西班牙专利ES2576748A1 Method and system for monitoring fiber optic networks (Machine-translation by Google Translate, not

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专利摘要:
Method and system for the monitoring of fiber optic networks. The present invention describes a method and a monitoring/monitoring system of an access optical network, which detects, prevents and localizes the failures of the deployed optical fibers and some network elements, and solves some of the problems presented by the prior art. The embodiments of the present invention propose an innovative system that makes it possible to detect, prevent and locate faults even in complex optical fiber networks point-to-multipoint, specifically in wdm-pon networks, in a flexible, precise manner, with a low maintenance cost, also allowing monitoring to be performed simultaneously with the provision of the service. (Machine-translation by Google Translate, not legally binding)
公开号:ES2576748A1
申请号:ES201530018
申请日:2015-01-09
公开日:2016-07-11
发明作者:María Del Carmen VÁZQUEZ GARCÍA；Alberto TAPETADO MORALEDA；David Ricardo SÁNCHEZ MONTERO；Julio MONTALVO GARCÍA
申请人:Universidad Carlos III de Madrid；
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专利说明:

image 1 DESCRIPTION
Method and system for monitoring fiber optic networks 5 TECHNICAL FIELD OF THE INVENTION
The present invention relates, in general, to the field of optical fiber networks and more specifically, to a method and system for monitoring the physical layer in passive optical networks.
10 BACKGROUND OF THE INVENTION
In recent years, due mainly to the increasingly widespread use of multimedia services (such as video on demand, internet television ...), the demand for bandwidth in telecommunications service access networks has increased considerably. Therefore, telecommunications operators have deployed new optical access and transport networks capable of improving their service portfolio and satisfying high demand requirements by consumers. For transport, operators have deployed a large-capacity transmission infrastructure, for example using optical fiber cables with multiple cable fibers (each cable is protected by a sheath and within the same cable, there are several optical fibers each with an outer jacket of different color that allows the unique identification of each fiber inside the cable). In this way the old copper cable based infrastructures have been replaced by optical networks of
25 access, which far exceed them in performance (bandwidth, scalability ...).
These access networks deployed by most operators are passive optical access networks (they are called passive networks because they do not use any active device that has to be powered remotely), also known as PON (Passive 30 Optical Networks) ”, Passive Optical Networks). The International Telecommunications Union has standardized these fiber optic access networks with a point-to-multipoint topology in different standards, for example, GPON (Gigabit Capable Passive Optical Network, Passive Optical Networks capable of Gigabits, ITU-T G. 984.1 ) X-GPON (English 10-Gigabit-capable passive optical network, Passive Optical Networks 35 capable of 10 Gigabits, ITU-T G. 987.1) and EPON (English Passive Optical Network Ethernet, Ethernet Passive Optical Networks, ITU-T 802.3ah -2004 -part 3) and are the
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more extended solutions used to provide broadband access over fiber.
PON networks usually have a point-to-multipoint tree structure; Thus, a large number (thousands or tens of thousands) of client installations are connected by means of 5 optical fibers to the same Central Office (also called CO of the English "Central Office") of the operator. Figure 1 shows an example of PON access network topology. As shown in this figure, MxN customer facilities (2) are connected to a single Optical Line Termination (OLT) termination (4) located in the rack (3) in the Central Office (1) of the operator. The transmission medium, the 10 fiber branches (6), connects the OLT (4) with the MxN Optical Network Units (ONUs), also called Optical Network Termination or ONTs of the English Optical Network Termination) (5) located in the client or user facilities (2). To do this, the fiber access infrastructure uses optical (passive) splitters of power 7a (1: M) and 7b (1: N) to divide the optical signal from the OLT (4) into the
15 different ONUs (5). The optical division can be carried out at a single point, but for deployment reasons, the optical power division is typically carried out at two levels as in the example shown. For the first level only one optical power splitter 7a is used, with one input and M outputs and for the second split level, there are M power optical splitters 7b, each with one input and N outputs.
20 The first generation of passive optical networks were TDM-PON networks, that is, they used Time Division Multiplexing (TDM). However, more recently, other PON networks have appeared that use another type of multiplexing, specifically WDM-PON networks. WDM-PON is an access technology
25 optical, which uses Wavelength Division Multiplexing Technology (Wavelength Division Multiplexing) as this technique allows more efficient traffic transport by offering users much faster access speeds than those achieved in the TDM-PON.
30 In this scenario, telecommunications operators have the challenge of supervising outdoor plants with point-multipoint topologies (with thousands of fiber branches), so that a low operational cost is achieved, while ensuring a low risk of interruption of the circuit and a fast recovery time in case of failures in the physical layer of the PON optical network, so that problems or defects that may appear in the
The physical layer should be detected and repaired in the shortest possible time.
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The detection of faults (ruptures, splices, defective contacts, incursions ...) is quite simple in point-to-point links, using reflectometric techniques, specifically using optical reflectometers in the time domain (OTDR) of the English "Optical Time Domain Reflectometers") . These techniques allow fault detection by sending
5 of optical pulses (also called optical pulses), the reception of reflections or echoes (for example, by Rayleigh scattering) and the measurement of the delay of the received echo (since damage to the fiber creates echoes and, therefore, the delay of the received echo allows to estimate its location while the analysis of the waveform and the spectrum of the echo helps to determine the type of damage caused by the echo).
10 However, this technique does not work in multipoint point networks (such as TDM-PON), since the echo signal received by the OTDR can consist, if there are damages in different fibers, in the sum of different reflected signals, so it is not possible to discern in a simple way in which of the many branches of fiber optic the fault occurs. To identify
15 Which fiber is failing, using this type of reflectometers, the reflectometry test should be repeated for each fiber of the optical cable, which is unfeasible in terms of resources, times and costs.
Some solutions have been developed in the prior art to solve the character
20 ambiguous of the location of the damages in this type of networks. For example, using tunable OTDRs located in the central office. But all these solutions are complex because it would involve using tunable lasers and a large number of tunable optical filters, which implies a huge cost.
25 Other monitoring solutions in passive optical networks with wavelength multiplexing, WDM-PON, also use OTDR to monitor the PON system, so that they require a switch to select which branch is monitored at any time, presenting the limitations previously described and the additional one that it takes a lot of time to detect the location of the fault in PON networks with a large
30 number of subscribers.
Other techniques for monitoring WDM-PON networks use different filters centered on different wavelengths in each of the branches of the network (for each client). This means having as many different filters as branches in the 35 point-to-multipoint optical access network, which implies a huge cost and also forces the operator to have an updated inventory of the different filters for maintenance (which associates each
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branch to its corresponding filter), which entails the risk of surveillance and maintenance errors.
The following are some documents of the prior art that propose 5 solutions for the detection of damages in PON networks:
Spanish patent ES2397024B1 proposes the use of a tunable laser source and optical reflectors, located on each delivery fiber, which reflect the light signals of a specific and individualized wavelength. The laser source emits to each of the 10 reflection wavelengths associated with the reflectors, in this way, and by means of a reception analysis equipment in the OLT, it can be determined, by means of the wavelength of the signal reflected the delivery fiber corresponding to each of the reflected signals. In addition to the drawbacks of using tunable lasers, another drawback of this system is that it is necessary to use different optical reflectors in
15 each of the delivery fibers of the PON network.
European patent EP2086133B1 presents a system in which the OLT generates a trigger signal that is received at each ONU. At the ONU, upon receiving this signal, a new upload signal is generated and received (OTDR analysis) in the OLT. Each ONU is assigned
20 a delay in the launch of the upload signal, thus, in the OLT it can be distinguished which delivery fiber each upload signal corresponds to. However, in this system it is necessary to install monitoring units in each of the ONUs, which increases the cost of the system against the use of optical reflectors and is also a fairly complex system due to the necessary synchronization between the OLT and all Un.
25 In the document Radio-frequency self-referencing system for monitoring drop fibers in wavelength division multiplexing passive optical networks ”IET Optoelectron., 2010, Vol. 4, Iss. 6, pp. 226-234 by J. Montalvo, D.S. Montero, C. Vázquez, J.M. Baptista, J.L. Santos presents a technique based on the measurement of the degradation of losses from
30 a reference and sensing signal (measured in the branch to be monitored). It uses a conventional AWG and the parameter used in monitoring is a relationship between powers in two different delay conditions and the delay to delay the reference signal and the measurement signal is performed in analogue way. This system requires two specific filters to monitor each branch, each with a specific wavelength range with the
35 consequential problems noted above. In addition, it does not allow monitoring with the channel in service.
image5 SUMMARY OF THE INVENTION
In view of the state of the art, an alternative solution is needed to detect and prevent failures in point-to-multipoint fiber optic networks in an efficient, cost-effective and
5 as exact as possible, that it solves at least part of the inconveniences presented by prior art systems. To this end, the present invention proposes a method and system of supervision and preventive monitoring of optical fibers, especially in WDM-PON access networks.
10 Specifically, in a first aspect, the present invention proposes a procedure for monitoring a fiber optic network that serves a set of customers, where said network has a set of fiber optic branches and at least one central office , the method being characterized in that it comprises the steps of:
a) Inject into the network, a first optical signal at a first wavelength;
B) Reflecting this first optical signal in a first reflector optical filter tuned to said first wavelength and receiving in this processing unit this first reflected optical signal;
C) Inject into the network, a second optical signal with a second wavelength other than the first wavelength, the bandwidth of this second optical signal being within a certain band, called a monitoring band;
d) In a cyclic AWG device, divide this second optical signal into signals
25 optics of different wavelengths and deliver each of these optical signals to the corresponding fiber optic branch of the set, where each branch of the set corresponds to the output of the AWG device, within the monitoring band, a length of determined wave different from the rest, where in each branch of optical fiber of the set there is a second reflector optical filter and where
All the second optical reflector filters of the branches have the same bandwidth, which comprises all the wavelengths corresponding to all the optical fiber branches of the assembly within the monitoring band;
e) In each of the branches to which the cyclic AWG device has delivered an optical signal, reflect in the second reflector optical filter of said branch and receive in the processing unit the signal reflected by each branch, and 6
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f) Determine the state of the set of fiber optic branches and the cyclic AWG device by analyzing the reflected light signals received in steps b) and e) in the processing unit.
5 The fiber optic network can be a Passive Optical Network that uses Wavelength Division Multiplexing, WDM-PON.
The first optical filter tuned to the first wavelength may be located on a stretch of fiber optic between the central office and a cyclic AWG device. For example,
10 may be located at the entrance of the cyclic AWG device. And even the first filter can be co-located with the AWG installed in its input fiber, or even integrated within the AWG component itself, so that it was not even necessary to install an additional component in the WDM-PON network, but the AWG itself already has the reflector integrated in its input. The cyclic AWG device can be in the external plant of the fiber optic network.
15 The first and second wavelengths belong to an optical band other than the optical band used to serve the customers of the fiber optic network. For example, the first wavelength may be 1490 nm and the second wavelength 1470 nm.
20 The processing unit can be in the central office and the first and second signals can be injected (downstream, that is, towards the user) from devices located in the central office.
The first optical signal may be a narrowband optical signal that comes from the first wavelength filtering of part of an optical signal generated by a broadband light source modulated by an Acusto-Optical modulator and the second signal. optics can come from the filtering centered on the second wavelength of the rest of the optical signal generated by the broadband light source modulated by the modulator
30 Acoustic-Optical. The bandwidth of the second optical signal can be much greater (more than 10 times) than the bandwidth of the first optical signal. The second optical signal can be broad bandwidth and contain components in all wavelengths corresponding to all branches of the assembly within the monitoring band, so in step d) the cyclic AWG delivers an optical signal of different wavelength
35 to each and every one of the fiber optic branches of the set.
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The status of each branch can be determined from the loss of power in each branch. To calculate the loss of power in each branch a phase detection can be performed. In particular, in one embodiment step f) comprises comparing the optical signal reflected by the filters of the fiber optic branches with the first optical signal reflected in the filter centered on the first wavelength and in one embodiment step f) comprises for each branch: - delay each other, the reflected signal coming from said branch and the first optical signal reflected in the first filter, - adding said delayed signals, - detecting the phase of said signal resulting from the sum of the delayed signals, - determine the loss of power in said branch from the phase detected.
In one embodiment in step f) the state of each branch is determined from the loss of power in each branch and to calculate the loss of power in each branch a relationship is made between optical powers detected for different delay conditions. Specifically, in one embodiment, step f) comprises for each branch: - delaying each other, the reflected signal coming from said branch and the first optical signal reflected in the first filter, - adding said delayed signals, - detecting the power ratio of the signals resulting from the sum of the delayed signals under two different delay conditions; -determine the loss of power in said branch from the ratio of detected powers.
The first optical reflector filter and each of the second optical filters may be Bragg Gratings (FBG) fiber filters. The optical filters located in each of the fiber optic branches may be between the cyclic AWG device and the client equipment that said fiber optic branch serves, for example, next to the client equipment or even incorporated into the equipment of client.
In one embodiment, the step of receiving in a processing unit the signal reflected by each branch of optical fiber comprises:
-Multiplex the light signals into a signal in the cyclic AWG device, each with a different wavelength, reflected in the filters of the different fiber optic branches; -Receive in another AWG device located in the central office, the signal multiplexed by the cyclic AWG device and demultiplex it obtaining the optical signals, each with a different wavelength, reflected in the second reflection filters of the different fiber optic branches ;
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5 - Deliver said reflected optical signals to the processing unit.
In one embodiment in step f) the power loss that has occurred in each branch is calculated and the status of the AWG device is determined from power losses
10 detected in all branches.
In a second aspect, the present invention proposes a monitoring system of a fiber optic network that serves a set of clients, where said network has a set of fiber optic branches and at least one central office, the procedure being
15 characterized in that it comprises:
-A light emission source configured to generate an optical signal,
-A first multiplexer-demultiplexer element configured to demultiplexer
20 the optical signal from a light emission source to obtain a first optical signal at a first wavelength and inject said first optical signal into the network;
-A second multiplexer-demultiplexer element configured for
25 demultiplexing the optical signal from a light source to obtain a second optical signal at a second wavelength and injecting said second optical signal into the network;
-A cyclic AWG device configured to split an optical signal that receives its
30 input, in signals of different wavelengths and deliver each of these optical signals to the corresponding fiber optic branch of the assembly, where each of the fiber optic branches of the assembly are connected to a different output port of said device and it corresponds, within a certain band, monitoring band, a determined wavelength different from the rest;
35 - A first reflector optical filter tuned to a first wavelength; 9
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-In each fiber optic branch of the set, a second reflector optical filter centered on the second wavelength, where all the optical filters of all branches have the same bandwidth that comprises all wavelengths, within the band monitoring, corresponding to the output of the cyclic AWG to all the fiber optic branches of the set and
-A processing unit with an optical receiver configured to receive the optical signals reflected by the filters, the processing unit being configured to detect problems in the set of optical fiber branches and in the cyclic AWG device by analyzing the signals of reflected light received.
In accordance with another aspect of the invention, a computer program product is provided, comprising computer executable instructions for carrying out any previously disclosed procedure, when the program is executed on a computer, on a digital signal processor , in a field programmable gate array (FPGA), in an application-specific integrated circuit, in a microprocessor, in a microcontroller, or in any other form of programmable hardware and also incorporates a digital data storage medium encoding a program executable by the machine to carry out any of the disclosed procedures.
Accordingly, according to the invention, a method, a system and a computer program according to the independent claims are provided. Advantageous embodiments are defined in the dependent claims. These and other aspects of the invention will be apparent and elucidated from the embodiments described in the following lines of the present specification. DESCRIPTION OF THE DRAWINGS
To complete the description that is being carried out and in order to contribute to a better understanding of the features of the invention, in accordance with a preferred example of its practical embodiment, accompanying said description as an integral part thereof, a set of drawings is offered in which, by way of illustration and not with a restrictive character, the following figures are represented:
Figure 1 shows a block diagram of an example of Passive Optical Access Network, PON.
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Figure 2 shows a graph with the wavelength response of a cyclic AWG device.
5 Figure 3 presents a block diagram of the proposed structure according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
The present invention can be embodied in other specific devices, systems and / or procedures. The described embodiments should be considered in all respects only as illustrative and not as restrictive. In particular, the scope of the invention is defined by the appended claims rather than by the
15 description of the figures included herein. All changes that are included in the meaning and scope of the claims must fall within its scope.
The present invention deals with the detection and prevention of failures in access networks of
20 optical fibers, WDM-PON. The embodiments presented are going to refer to these types of networks, but the embodiments are also applicable to other types of networks.
The embodiments described below solve some of the problems found in the prior art monitoring techniques. These
25 embodiments represent an innovative proposal, which refers in particular to a preventive monitoring method and system that allows to accurately detect faults even in WDM-PON point-to-multipoint fiber optic access networks in an economical, fast, simple way and accurate.
30 As explained above, WDM-PON networks are passive fiber optic access networks that use Wavelength Division Multiplexing (WDM) to perform point-multipoint communication between one (or several) Operator's Headquarters of telecommunication and many users (customers) of said operator (or more specifically between the OLT located in the Central Office of the Operator and each of the UN located in
35 each installation of each client). WDM-PON networks often use AWG devices (waveguide grid array, English "Arrayed Waveguide Grating") to separate the different wavelengths, each of which is addressed to a user.
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These devices are usually used as optical demultiplexers, so that they are able to separate, from an optical signal (also called a light signal or light signal), which goes through a single optical fiber, signals of different wavelengths that routes to different output ports, connected to each of the fiber optic branches that goes to each of the users' UNs, allowing point-to-point communication. In other words, an AWG device divides the light that comes from a light source into different light components, each centered on a wavelength i (1 ≤ i
10 ≤ R), where R is the number of branches / customers served by the AWG.
Of course, the AWG device is also used as a multiplexer, being able to multiplex a high number of signals of different wavelengths into a single signal that transmits through a single optical fiber. These devices are based on a fundamental principle
15 optical, that in a fiber optic network, a good number of channels of different wavelength can be transported in a single optical fiber without the cross interference between them being appreciable.
In the system proposed in the present invention, an AWG device will also be used,
20 but in this case it is a cyclic AWG device; unlike some state-of-the-art solutions where non-cyclic AWGs are used. A non-cyclic AWG device separates the signal (or input signals) into signals of different wavelengths (called channels) and delivers a single-length signal to each AWG output port (that is, each fiber optic branch). wave (in a certain band). However the
The cyclic AWG device (to be used in the present invention) has a periodic response, whereby each output port will route signals of a certain wavelength and signals of wavelengths equidistant with that first wavelength ( in the same band or in different bands).
30 In other words, a cyclic AWG has a periodic response so that each AWG output branch encompasses a channel in a given band and also other equispaced channels (from the point of view of wavelength) in it optical band or other bands. Thus, with cyclic AWGs, the same output branch can be used simultaneously in several optical bands. Typically for bidirectional communication
One band is used for one direction of data transmission and another for the opposite direction or, as in the present invention, one band will be used to serve the customers and another
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for monitoring. A non-cyclic AWG does not have a periodic response, so that each branch only lets one channel (a signal of a certain wavelength) pass through the corresponding band.
To explain its operation more clearly, Figure 2 shows a graph with the wavelength response of a cyclic AWG device with 32 branches (R = 32). The figure shows branches 1 (in a continuous line) and 32 (in a broken line). As can be seen, each branch operates simultaneously in several bands due to the cyclic operation of the AWG. Within each band there will be signals of different wavelengths that can belong to different branches.
In the present invention, the characteristics of the cyclic AWG (where signals from different bands or optical ranges can be found in each branch) are used to perform the monitoring using signals in an optical band other than that of the channel in service (i.e. band used by the telecommunications operator to provide service) and, therefore, monitoring (fault detection) is performed while the branch is in service (which is one of the advantages of the present invention). In some prior art solutions, a cyclic AWG is used, but only for data transmission in both directions of transmission, using a band (cycle) for one direction of the service signals (user-central direction) and another band (cycle) for the opposite direction of the service signals (central-user direction), so they only use two cycles of the cyclic AWG. But in no prior art solution, an additional third band (cycle) of the cyclic AWG is used to perform monitoring using signals in an optical band other than the service band (s); that is, in the present invention the cyclic AWG is used in three cycles (bands), two for the service signals and a different one for the monitoring signals, unlike in the rest of the prior art solutions where or not AWG cyclic is used or only used in two cycles for simultaneous data transmission in both directions of transmission.
In one embodiment, the S band (1460-1530 nm) can be used for monitoring and the C (1530-1565nm) and L (1565-1625nm) bands for the communication (service) channels; although of course, other combinations of bands are also possible.
On the other hand, the proposed system also uses only one type of filter (reflection) in each of the branches to be monitored. As it has been seen, in solutions of the state of the art, the filters used in each branch to be monitored are centered in wavelengths
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different (each filter will be centered on the wavelength corresponding to the fiber optic branch in which it is located) and, therefore, it is necessary to use different filters on each outgoing branch of the AWG or equivalent (with the consequent inventory problems and maintenance discussed above). However, in the solution proposed here, the reflection filters placed on each AWG output branch reflect the entire range of wavelengths used for monitoring (for example, an entire optical band), therefore independently of the branch at the If the filter is connected, the corresponding monitoring wavelength will be reflected. That is, in the present invention equal filters (covering the same range of wavelengths) are used in all branches (therefore interchangeable), so inventory activities are simplified (by using the same filter for all the branches do not have to keep a strict inventory that associates each branch with its corresponding filter) and maintenance, and consequently the network costs are reduced. Therefore, the present invention uses a "colorless" monitoring topology (absence of color) that is, independent of the wavelength of the channel.
In the proposed solution, to perform the monitoring, for each of the fiber branches there is an optical monitoring signal (or measurement) and a common optical reference signal. Through a heterodyne detection the small power variations of each of the branches are detected (comparing the common reference signal with the measurement signal reflected in each branch), which indicate or the degradation in losses that occurs and, at from it, the current presence of a branch failure can be detected or the possibility of a future branch failure can be predicted. As will be explained later, from this comparison, failures can also be detected in other devices of the fiber optic network, such as in the AWG. This processing takes place in the central office.
That is, the proposed invention allows to detect not only total losses of the signal in the branches that indicate a current fault but also attenuations of the optical signal in the branches (although they are very slight), whereby a deterioration of a certain branch or AWG device before breakage or serious failure occurs and act accordingly; Therefore, contrary to the existing solutions, the present invention allows us to develop a task not only for detecting failures but also for preventing them (therefore being able to act before the failure avoiding the interruption of service).
The present invention allows detecting attenuations in sections of the optical network much milder than those that allow detecting the solutions of the state of the art and that even the
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They pick up some of the current standards. Thus, in some of these standards (for example in SFF-8472 or ITU-T G.984.2 Physical Media Dependent (PMD) layer specification (Amd2, Appendix IV), March 2008) a precision in the measurements of ± 3dB is required, while In the present invention, accuracies can be obtained in attenuation measurements much less than 1 dB.
The present invention can be used in combination with other state-of-the-art technologies (for example, OTDR) if it is desired to locate where the fault occurred in the exact branch. That is, the present invention can be used to detect even very minor problems in some of the branches and then use another technique of those already existing to locate at which point of the branch the problem has occurred.
A schematic of the proposed structure according to an embodiment of the present invention is presented in Figure 3. It shows a WDM-PON access network, in which there are a number of elements installed in a central office of a telecommunication operator and other elements located in an external plant.
First, we see that there is an external fiber optic infrastructure, which is branched so that from each of the output ports (32b) of the cyclic AWG device (32) there is a branch of optical fiber (33) that will each client unit or unit (ONU) (34) located in each of the client's facilities. This AWG device will divide the light it receives at its input (32a) into different light components each centered on a different wavelength, each of which will go to a different fiber optic branch. If the number of AWG outputs is R (in other words, the AWG serves R optical branches at the output), each of these outputs will correspond to a single optical signal of a different wavelength iM (1 ≤ i ≤ R) within the monitoring bandwidth (also called band), and, when the AWG receives an optical signal at the monitoring bandwidth, at its input (32a), it will divide it into iM wavelength components ( for those longiM wavelengths that exist in the optical input signal) and will deliver that component to its corresponding branch. If the optical input signal of this AWG has sufficient bandwidth to have optical components in the wavelengths of all branches, the AWG will deliver R signals of different wavelengths (each to a corresponding branch). Of course, if the optical input signal does not have sufficient bandwidth (that is, it does not have optical components at all wavelengths of all branches within the monitoring bandwidth), then the AWG will only deliver to its output, optical signals length of
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iM wave for those iM wavelengths that exist in the optical input signal. In the example in the figure, the number of branches (customers) is 32 (although only 3 are shown for clarity). On the other hand, the AWG will perform the opposite function, multiplex the signals it receives from each branch to form a single multiplexed signal that it will send to the central office.
Being a cyclic AWG, each AWG output branch encompasses a channel in a given band and also other equally spaced channels. That is, each output will correspond not only to one wavelength in the monitoring bandwidth, but to other wavelengths equiespaced outside that monitoring bandwidth. Thus, for example, also in the service band, each of the AWG outputs will correspond to an optical signal of a different wavelength iS (1 ≤ i ≤ R) within the service band, and, when the AWG receives an optical signal in the service band, will divide it into deiS wavelength components (for those iS wavelengths that exist in the optical input signal) and deliver that component to its corresponding branch.
The bandwidth of the signal used to monitor will be narrow enough not to cover more than one wavelength component of those corresponding to each branch (that is, not to "get into" another AWG cycle). In addition, it is usually wide enough to cover all the optical branches that leave the AWG, that is, to have a component (but only one) of the wavelength corresponding to each branch. If the monitoring signal does not cover all branches, only some of them will be monitored (which may be of interest in certain applications).
In Figure 3, a single cyclic AWG appears (located in a remote location on the external floor) that serves all the clients of the network but there may be two or more cyclic AWGs (functioning as shown in the previous paragraphs), each of them serving a certain number of clients in the network.
In addition, according to a preferred embodiment of the present invention, there is a filter at the entrance of the AWG, which we will call reference filter (36) and a filter (35) in each of the fiber optic branches (which we will call branch filters), located at the entrance (or at least near) the client equipment. In one embodiment, these branch filters may even be part of (be incorporated in) the client equipment (of the ONU / ONT), so that it is not necessary to install them specifically in the branch when they are already integrated in 16 10
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each team. All these filters will be reflection filters (also called optical reflectors) since they behave reflecting (at least in part) signals whose wavelength is in a certain range of wavelengths and letting the rest of the signals (whose length of wave is not in a certain range of wavelengths). The range of wavelengths that the filter reflects (called the range or bandwidth of the filter) can be very narrow (so that in practice it would only reflect signals of a single wavelength) or be wider (so in the practice would reflect signals of a more or less large set of wavelengths).
These filters can be any type of reflection filters but preferably they will be FBG filters (network filters or Bragg fiber optic grid). These FBG filters can be tuned (centered) at the desired wavelength and have a bandwidth (range of wavelengths they reflect) around said central wavelength. As mentioned, the branch filters are all centered on the same wavelength and cover the same range of wavelengths, while the reference filter, as will be explained later, is usually centered on another wavelength other than of the branch filters and be narrower (although normally this wavelength will belong to the same optical band as the wavelength of the branch filters).
Then, having one filter per branch and one reference, the number of filters needed in the proposed monitoring system is R + 1 (where R is the number of branches or customers of the network). In solutions of the state of the art, two specific filters are used to monitor each branch, then the number of filters needed would be 2R, much higher than in the proposed solution (so the proposed solution is much less complex and expensive than solutions of the state of the art, especially considering that the number of clients of the network is usually very high).
In this embodiment, there is a broadband light source (37) (BLS), a signal generator (38) and an Acusto-Optical modulator (39) (AOM), "Acousto Optic Modulator ”) that modulates the light signal generated by the source (37) according to the signal generated by the generator (38). These items may be located in the Central Office. This signal will be a broad optical spectrum signal that will include at least a first and second wavelength. The first and second wavelength can be 1490 nm and 1470 nm respectively, although of course other wavelength values can be used. The output of this modulator goes to a coupler (310) that divides the light signal from
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so that most (99% according to the example shown in Figure 3 although other percentages of division can be used) go to circulator 2 (312), (and hence through the demux element (321) and the AWG external (32), to customers' equipment through fiber optic branches). The rest (1% according to this example) goes to circulator 1 (311) (and from there through the demux element (320), to the reference reflector filter). This smaller part of the light source that goes to the circulator 1 is the one used as a reference signal and allows to obtain the self-reference property of the measurement system.
In this embodiment, there are also two wavelength-multiplexer (demuxmux) wavelength elements (320 and 321), which will serve to extract (filter) and introduce the monitoring signals into the optical network (together with the service signal) and to separate the monitoring signals once reflected by the respective filters. These elements can be, for example, Multiplexing elements by Vivid Wavelength Division (CWDM), although other types of multiplexer-multiplexers can be used.
The first of these elements (320) receives the output of circulator 1 (311) through port 320a and demultiplex (filters) in a narrow range signal (for example 0.5nm although other ranges are possible) centered on the first length wave (for example at 1490 nm), which is routed to output 320b and from there to the reference filter (where it will be reflected). The rest of the signal that it receives through port 320a is routed through port 320c to the transmitter / receiver (317). Likewise, this element (320) will extract, from the reflected signals it receives at its port 320b, a signal centered on the first wavelength (reflected reference signal) and deliver it to the processor 313 (through port 320a). The rest of the signal that it receives through port 320b (which will be a signal of the optical communication service), routes it through port 320c to the transmitter / receiver 317.
The second of these elements (321) receives the output of circulator 2 (312) through port 321a and demultiplex (filters) in a signal of a certain range (for example 5nm or 20 nm although other ranges are possible) centered on the second wavelength (for example at 1470 nm) that leads to the 321b output and from there to the external AWG (32) and subsequently to the clients' equipment through the fiber optic branches (where they will be reflected by the filters of branch). The rest of the signal that it receives through port 321a routes it through port 321c to the other demux element (320). Also this element
(321) will extract, from the signals reflected by the network it receives at its port 321b, signals centered on the first wavelength (reflected monitoring signals) and the
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will deliver to processor 313 (through port 321a). The rest of the signal that it receives through port 321b, routes it through port 321c to the other demux element (320).
The signal of the optical communication service emitted by the transmitter / receiver 317, being in a band other than the monitoring band (that is, it does not include either the first or second wavelength signal) will not be affected by these demux elements that the only thing they will do with it is to receive it through one of its ports (320c or 321c) multiplex it with the signals they receive from other ports and deliver it to another of its ports (320b or 321b) so that it reaches customers, allowing offer the communication service to customers simultaneously to the monitoring of the WDM-PON network.
All these elements are typically found in the operator's central office.
In the central office of the operator there is the signal processing unit (DSP) of the “Digital Signal Processing”, which will be responsible for measuring and analyzing the reflected signals (through digital signal processing) those reflected by the branches as the reference) to detect possible failures in the branches. This processing unit will have among other elements, digital analog converters, optical detectors (photodetectors in English) sensitive to wavelength and in general all the elements necessary to receive, measure and analyze the reflected optical signals. This unit will preferably work in a self-referenced manner, that is, that the result of the measurements (and therefore of the analysis performed) is independent of absolute variations of parameters external to the fiber segment that is monitored, which would distort and even do totally The result was wrong. For example, in this specific case, what you want to measure is the optical attenuation (from there to detect the defects of the fiber) between the AWG input port and the end end of each AWG output branch that connects to a client computer (ONU). The self-reference allows that if, for example, the power of the light source (laser) located in the plant changes due to aging or temperature effects, or the fiber that connects the plant with the AWG is attenuated, the parameter of Attenuation of each branch of the AWG does not vary since a mathematical quotient is used that cancels the effect of variations in the parameters outside the measurement segment.
In the central office there would also be a second AWG (316) (which can be cyclic or non-cyclic) that would receive the single signal resulting from multiplexing in the AWG of the external plant (32), the signals reflected by the different optical branches and the will divide into light signals from
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Different wavelengths, each of which will go to a different output channel that will be delivered to the processing unit. That is, in the processing unit the reflected signal will be separated in different wavelengths, each corresponding to one of the R optical branches. The number of outputs of the second AWG will be R (as well as the first) and each of these outputs will be assigned a single optical signal of a different wavelength iM (1 ≤ i ≤ R) within the monitoring bandwidth . In other words, what this second AWG does is recover the separate signals reflected by each optical branch, which the first AWG (32) has multiplexed together.
Also in the central office there would also be an optical transmitter / receiver (317) that will be responsible for the transmission and reception of the optical signals of the communication service that is being provided to the clients of the access network. These signals will have a wavelength belonging to bands other than monitoring, so they will not be reflected by the reference filter or by the branch filters and will reach the customer's equipment. In one embodiment, these service signals will be in the C band, for example, around 1550 nm in the user-central direction, and in the L band, for example, around 1600nm, in the central-user direction. But of course other bands and other values can be used. These service bands (bandwidth in which the service signals are located) will be different from the monitoring band (bandwidth in which the monitoring signals are located, both the reference and the ones sent to the branches); This, together with the cyclic AWG, allows monitoring to be done simultaneously with the provision of the service.
In one embodiment of the present invention, monitoring will be performed following the following steps:
-The monitoring system sends an optical signal (also called optical signal or light signal) (314) of reference (for example an optical pulse) at a first wavelength. This optical signal will be the signal from the BLS light source (37), after passing through the modulator (39) and the coupler (310). This signal is injected into the PON network using circulator 1 (311) and the first demux (320) that performs filtering at that first wavelength of the output of the wide spectrum source, after circulator 1. This signal will have a relatively narrow bandwidth (for example 0.5 nm). This first wavelength will be within the range of the reference filter (36) located at the entrance of the first AWG (32) in the external plant. In fact, in one embodiment this first wavelength will be the central wavelength of said reference filter. The reference signal when arriving at the reference filter will be reflected (since the wavelength of this signal is within the range of the reference filter) and returns (318) to the central office. Specifically, it returns to circulator 1, thanks to the demux selection (320), which will deliver it to the processing unit (313). In one embodiment this first wavelength is in the S band,
image10
5 having a value for example of 1490 nm. But of course other bands and other values can be used for the first wavelength.
-An optical signal (also called a light signal or a light signal) is sent for monitoring (315) of broad optical spectrum at a second wavelength. This optical signal 10 will be the signal from the BLS light source (37), after passing through the modulator (39) and the coupler (310). This signal is injected into the PON network using circulator 2 (312) and the second demux (321) that performs a filtering on that second wavelength of the output of the wide spectrum source, after circulator 2. This signal will arrive to the cyclic AWG and will not be reflected by the reference filter (36) of the AWG input, since
15 that this second wavelength will be different from the first wavelength and will be outside the reflection range of the reference filter.
-In the cyclic AWG this signal will be divided into signals of different wavelengths, each of which will go to one of the optical branches that goes to each client team. Typically this signal will have a bandwidth large enough to cover all the optical branches that exit the cyclic AWG (32); that is, following the example explained above, this signal will be centered on the second wavelength and would cover the entire range of wavelengths used for branch monitoring (iM, 1 ≤ i ≤ R). If the monitoring signal does not cover all this bandwidth, then only
25 some of them (which may be of interest in certain applications) will be monitored (only a monitoring signal will arrive).
The signal that goes through each of the branches will meet the reflector filter of each branch. The reflector filters used in the branches will be centered on this second wavelength and, as explained above, these filters have sufficient bandwidth to cover (and therefore reflect) the entire range of wavelengths used to branch monitoring (iM, 1 ≤ i ≤ R); therefore all filters can be the same, and it is not necessary to know the operating wavelength of each port to select the corresponding filter, facilitating the installation of this type of systems and reducing its complexity. The signal that goes through each one of the branches will have a different wavelength iM but, when covering the reflector filters of each branch all the lengths of
image11
Wave, in all branches the signal will be reflected by each of the reflector filters and will return to the cyclic AWG, which will multiplex all the reflected signals forming a single optical signal (319) that will be sent back to the central office. Specifically, it returns to circulator 2, after being selected by demux (321) centered on the band of lengths of
5 branch wave, which will deliver it to the second AWG (316).
In an embodiment this second wavelength is in the S band having a value, for example, of 1470 nm and the bandwidth of the reflectors and the monitoring signal will be 20nm. But of course other bands and other values can be used for
10 first wavelength. For example, in an experiment carried out to test the system a bandwidth of 5nm was used (so that only one of the outgoing branches of the cyclic AWG was covered and, therefore, monitoring was not done in all branches of all customers).
15 -The AWG (316) would receive the unique signal resulting from multiplexing in the AWG of the external plant
(32) the signals reflected by the different optical branches and will demultiplex them. That is, it will divide the signal it receives into light signals of different wavelengths (the one corresponding to each channel), each of which will correspond to the signal reflected in one of the monitored fiber optic branches (33).
20 The signal reflected by each of the branches will have a different wavelength (the one corresponding to each branch, iM (1 ≤ i ≤ R)) and said reflected signal will be attenuated in its path differently depending, not only on the fiber wavelength of each branch, but also the state or possible failures in the fiber infrastructure in that branch.
25 For example, a bent cable or a dirty connector may produce optical attenuation on an AWG branch and that would cause the signal reflected on that branch to be lower than normal. All reflected signals are received in the processing unit (313). This processing unit will compare the reflected reference signal (at the first wavelength) with the reflected signal received from each branch (at different wavelengths but at
30 the environment of the second wavelength), to calculate the attenuation of each branch and, from the attenuation, will quickly determine if there is or may be any problem in that branch. When the digital processing is carried out, its development is virtually possible on a PC (personal computer), which allows a more immediate remote reconfiguration.
In addition, through this processing of the reflected signals, possible operation failures can also be detected in the cyclic AWG itself (32). Under normal conditions this device has fixed losses (always the same) of a few decibels between the input and each of its output ports; if the AWG suffered any failure, which affected all branches simultaneously, similar additional attenuation would be detected in all branches, so it would be detected that in that device or at that point of the passive fiber network, it can there is a problem (flood, blow by manipulation
image12
image13
or accident, temperature outside the operating range, etc ...) since the attenuation introduced by the AWG has varied.
The processing unit will perform the radio frequency processing, since the optical signals are electrically modulated by the AOM modulator (39). This allows to improve the robustness of the system against electrical noise that could interfere with continuous signals if the optical signals were not modulated, as well as allow a greater resolution of the system in terms of the level of variation of optical power to be measured.
This processing can be done in several different ways. For example, the processing may comprise a phase detection. Specifically, in one embodiment what is done is, for each branch i, offset (delay) the reflected signal from the branch and the reference signal received from each other in the processor (313) (after passing through photodetectors to convert them in electrical signals and usually also through bandpass filters to keep the band of interest and thus reduce the noise). The outdated (delayed) signals are then added, so that the phase of the resulting signal depends only on the amplitude variations of each branch and not on the power fluctuations of the source or link common to both signals. Thus the amplitude variations are converted into phase variations, whereby a phase detection can be performed and from said phase detection, the losses (attenuations) of the signal that occur in each branch can be obtained. This allows the detection of very slight attenuations that would not be detected using another type of processing.
The phase dependence of the resulting electrical signal after its detection with the losses in the analyzed branch is determined by the following expression:
 without   without  
Ri Yes
 arctg 
cos  cos  (1)  i  
 R Yes
image14
where Φi is the phase detected, R is the angular frequency with which the electrical signal that modulates the optical signal is offset to the wavelength of the reflected reference signal received, If it is the angular frequency with which it is offset the electrical signal that modulates the optical signal at the wavelength of the reflected signal received from each branch i,
5y i are the losses in each of the branches "i". Therefore, through this equation, through the detection of the phase Φi the losses in that branch can be obtained.
Selecting the specific delay values R and Si (which can be the same for all branches or using different delay values on each branch) can cause the
10 behavior is more or less linear and with a greater or lesser sensitivity.
To make the phase detection, a fixing amplifier (in English “lock-in”) is usually used that allows to measure and detect (extract) electrical signals, even of low power, in a certain wavelength with great precision in a Very loud channel Specifically, the
The signal resulting from adding the delayed reflected signals is passed through this amplifier which, using a phase tuning algorithm (phase locked loop algorithm) and a demodulation stage, allows the signal phase to be detected. To do it more precisely, the “lock in” amplifier also takes into account the original reference signal.
20 Detecting losses in this way, by phase detection, allows detecting very small signal attenuations, so that a deterioration of a certain branch can be detected before breakage or serious failure occurs in that branch and act in consequence; whereby the present invention allows to develop a work not only for detecting failures but also for preventing them.
25 The embodiment presented in the previous paragraphs of attenuation detection by phase measurement is only one possible implementation of a self-reference attenuation detection technique. Any other of the many known techniques could be used, for example, those based on the ratio of output powers to two
30 different delay conditions for the reference signal and the signal of each branch. These techniques (which monitor the ratio of powers in 2 different delay conditions) involve the use of 2 lock-in amplifiers per branch, while the one proposed above (which monitors the phase with a single phase, delay, relative condition since it is enough to put a lag, delay, relative between both signals) just
35 need a lock-in amplifier per branch.
image15
In summary, the proposed monitoring method and system employs cyclic AWGs together with equal reflector filters in each branch, where one of the AWG cycles corresponds to an optical band dedicated to monitoring, while other bands can be used simultaneously for data transmission. in both directions of transmission. The present invention presents a fast and flexible economic method and system for the supervision and monitoring of optical fibers in WDM-PON networks. The proposed solution allows to optimize the number of filters used (one per fiber branch) and also allows the development of a “colorless” monitoring topology, that is, independent of the wavelength, so that the filters used in each branch They are equal and therefore 10 interchangeable. In this way, the same type of reflector can be connected to any branch in an indifferent way, because they all work at all wavelengths of the monitoring band, simplifying inventory and maintenance activities, thus avoiding errors and the cost of the network is minimized. In prior art solutions, it was necessary to use a different reflector (or pair of reflectors) on each branch. 15 Together with the use of frequency modulation and virtual delays (they are performed by software on the signals acquired from the branch and the reference), it allows software processing that offers greater flexibility, precision and reconfiguration. In previous schemes, the use of analog delays and expensive lock-in amplifiers was proposed. In addition, the proposed invention allows a great precision and sensitivity in the detection, so it allows to detect very slight attenuations of the optical signal in a certain section of optical fiber, so that small deteriorations can be detected before breakage occurs or serious failure in that branch and act accordingly; therefore, contrary to the existing solutions, the present invention allows to develop a work not only for detecting failures but also for preventing them with more precision than previous techniques (therefore, it is possible to act before the failure avoiding interruption from service). In addition, with the proposed method and system, monitoring can be performed while the channel is in service but traveling the same path as the signal used to provide the service; so you can do a very reliable monitoring of the infrastructure used for the service without requiring
30 the interruption of the same nor to carry out the monitoring at hours in which no service is provided. As explained, the present invention not only detects failures in the fiber optic branches but also allows to detect possible operating failures in the AWG itself.
This technology has a high potential in any type of access networks, but especially in access networks for businesses where high security and reliability are required, as well as in metropolitan networks and in converged fixed-mobile networks.
image16
Although in some of the embodiments specific values were presented for some parameters such as the wavelengths used, the monitoring and service bands, the bandwidth of the filters and the input signals ... it will be evident to the expert in the matter that other types of securities may be used herein
5 invention without departing from the scope thereof.
The person skilled in the art will notice without difficulty that various procedures described above can be carried out by programmed computers. Here, some embodiments are also intended to protect the 10 program storage devices, for example, digital data storage media, which are instruction programs executable by computer or executable by coding machines and readable by computer or machine, in which said instructions carry out some or all of the steps of said procedures described above. Storage devices
15 programs can be, for example, digital memories, magnetic storage media, such as magnetic disks and magnetic tapes, hard disk drives or digital optically readable data storage media. The embodiments are also intended to protect the computers programmed to execute said steps of the procedures described above.
The description and drawings simply illustrate the principles of the invention.
The present invention has been described with reference to specific embodiments, it should be understood by those skilled in the art that the
25 and various different changes, omissions and additions in their detailed and precise form without departing from the scope of the invention as defined by the subsequent claims. Some of the steps of the methods described above can be performed in a different order from the above.
30 Likewise, all the related examples herein are for pedagogical purposes only to help the reader understand the principles of the invention and the contribution concepts of the inventor (s) to extend the technique should be interpreted without purpose. limiting to such examples and specifically related conditions. Likewise, all the declarations of the present memory, principle devices,
Aspects and embodiments of the invention, as well as its specific examples are directed to encompass the equivalents thereof.
image17
It should be appreciated by those skilled in the art that any block diagrams inserted herein represent conceptual views of illustrative circuit assemblies that incorporate the principles of the invention. Similarly, it should be appreciated that any flow maps, flow charts, transition diagrams of
5 states, pseudocode and the like, represent various processes that can be substantially represented in a computer-readable medium and thus executed by a computer or processor, whether or not such computer or processor has been explicitly shown.

权利要求:
Claims (16)
[1]
image 1
1. Method of monitoring a fiber optic network that serves a set of
customers, where said network has a set of fiber optic branches (33) and at least one central office, the method being characterized in that it comprises the steps of:
a) Inject into the network, a first optical signal (314) centered on a first wavelength;
10 b) Reflecting this first optical signal in a first reflector optical filter (36) tuned to said first wavelength and receiving in a processing unit
(313) this first reflected optical signal;
c) Inject into the network, a second optical signal (315) centered on a second
15 wavelength other than the first wavelength, the bandwidth of this second optical signal being within a given band, called the monitoring band;
d) In a cyclic AWG device (32), divide this second optical signal into signals
20 optics of different wavelengths and deliver each of these optical signals to the corresponding fiber optic branch of the set, where each branch of the set corresponds to the output of the AWG device, within the monitoring band, a length of determined wave different from the rest, where in each branch of optical fiber of the set there is a second reflector optical filter (35) and where
All the second optical reflector filters of the branches have the same bandwidth, which comprises all the wavelengths corresponding to all the optical fiber branches of the assembly within the monitoring band;
e) In each of the branches to which the cyclic AWG device (32) has
30 delivered an optical signal, reflect in the second reflector optical filter (35) of said branch said signal and receive in the processing unit (313) the signal reflected by each branch and
f) Determine the state of the fiber optic branch assembly and the AWG device
35 cyclic (32) by analyzing the reflected light signals received in steps b) and e) in the processing unit (313).
image2
[2]
2. Method according to any of the preceding claims wherein the fiber optic network is a Passive Optical Network using Wavelength Division Multiplexing, WDM-PON.
5
[3]
3. A method according to any of the preceding claims wherein the first optical filter (36) tuned to the first wavelength is located in a section of fiber optic between the central office and a cyclic AWG device (32).
Method according to any of the preceding claims wherein the first and second wavelengths belong to an optical band other than the optical band that is used to service the customers of the fiber optic network.
[5]
5. Method according to any of the preceding claims wherein the first wavelength is 1490 nm and the second wavelength is 1470 nm.
[6]
6. Method according to any of the preceding claims wherein said processing unit is in the central office and the first and second signals are injected from devices located in the central office.
twenty
[7]
7. Method according to any of the preceding claims wherein the second optical signal is broad bandwidth and contains components in all wavelengths corresponding to all branches of the assembly within the monitoring band, so that in the step d) the cyclic AWG delivers a different optical signal
25 wavelength to each and every one of the fiber optic branches of the set.
[8]
8. Method according to any of the preceding claims, wherein in step f) the state of each branch is determined from the loss of power in each branch and to calculate the loss of power in each branch a detection of phase.
30
[9]
9. Method according to any of the preceding claims, wherein step f) comprises for each branch: - delaying each other, the reflected signal from said branch and the first optical signal reflected in the first filter (36),
35 -summing said delayed signals, -detecting the phase of said signal resulting from the sum of the delayed signals; -determine the loss of power in said branch from the phase detected.
image3
[10]
10. Method according to any of the preceding claims 1-7, wherein in step f) the state of each branch is determined from the loss of power in each branch
5 and to calculate the power loss in each branch, a relationship is made between optical powers detected for different delay conditions.
[11]
11. Method according to any of the preceding claims wherein said first optical signal is a narrowband optical signal that comes from filtering.
10 centered on the first wavelength of part of an optical signal generated by a broadband light source (37) modulated by an Acusto-Optical modulator (39) and the second optical signal comes from the filtering centered on the second length of wave of the rest of the optical signal generated by the broadband light source (37) modulated by the Acusto-Optical modulator (39).
fifteen
[12]
12. Method according to any one of the preceding claims, wherein the first reflector optical filter and each of the second optical filters are Bragg's fiber filters, FBG.
Method according to any one of the preceding claims, wherein step f) comprises comparing the optical signal reflected by the filters (35) of the fiber optic branches with the first optical signal reflected in the filter (36) centered on The first wavelength.
[14]
14. Method according to any of the preceding claims wherein the filters
25 optics (35) located in each of the fiber optic branches, are incorporated into the client equipment that each branch serves.
[15]
15. Method according to any of the preceding claims, wherein the step of
receiving in a processing unit the signal reflected by each branch of optical fiber 30 comprises:
-Multiplex in a signal in the cyclic AWG device (32) the light signals, each with a different wavelength, reflected in the filters of the different fiber optic branches;
35 -Receive in another AWG device (316) located in the central office, the signal multiplexed by the cyclic AWG device and demultiplex it obtaining the optical signals, each with a different wavelength, reflected in the second reflection filters of the different fiber optic branches;
image4
5 - Deliver said reflected optical signals to the processing unit.
[16]
16. Method according to any of the preceding claims, wherein in step f) the loss of power that has occurred in each branch is calculated and the status of the AWG device is determined from power losses detected in all
10 branches
[17]
17. Monitoring system of a fiber optic network that serves a set of customers, where said network has a set of fiber optic branches (33) and at least one central office, the procedure being characterized in that it comprises:
15 -A light emission source configured to generate an optical signal,
-A first multiplexer-demultiplexer element (320) configured to demultiplex the optical signal from a light emission source for
20 obtaining a first optical signal at a first wavelength and injecting said first optical signal into the network;
-A second multiplexer-demultiplexer element (321) configured to demultiplex the optical signal from a light emission source for
25 obtaining a second optical signal at a second wavelength and injecting said second optical signal into the network;
-A cyclic AWG device (32) configured to divide an optical signal that it receives at its input, into signals of different wavelengths and deliver each of
30 these optical signals to the corresponding fiber optic branch of the assembly, where each of the fiber optic branches of the assembly are connected to a different output port of said device and corresponds, within a certain band, monitoring band, a certain wavelength different from the rest;
35 - A first reflector optical filter (36) tuned to a first wavelength; -In each fiber optic branch of the set, a second reflector optical filter (35), where all optical filters (35) of all branches have the same bandwidth that comprises all wavelengths, within the band of monitoring, corresponding to the cyclic AWG output to all branches of
image5
5 set optical fiber and
-A processing unit with an optical wavelength sensitive receiver configured to receive the optical signals reflected by the filters, the processing unit being configured to detect problems in the set of branches
10 of optical fiber and in the cyclic AWG device (32) by analyzing the reflected light signals received.
[18]
18. A computer program product comprising a computer program code adapted to carry out the procedure in accordance with any of the
Claims 1 to 16 when said program code is executed on a computer, a digital signal processor, an FPGA, an application-specific integrated circuit, a microprocessor, a microcontroller or other form of programmable hardware.

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