• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    PURPOSE: An apparatus for checking a frequency using optical filters having different transmission characteristics is provided to use an optical fiber and a pilot tone which is used for checking the existence and the size of an optical signal in an optical transmission system based upon multi wave division method in order to manage and maintain the system efficiently. CONSTITUTION: A first shaping coupler(111) extracts an optical signal from an externally inputted optical signal. A second shaping coupler(112) equally divides the signal inputted from the first shaping coupler(111). A first and a second optical filters(113,114) filter different bandwidth transmission filtering with respect to a signal inputted from the second shaping coupler(112). A first and a second optical detectors(115,116) measure the intensity of the optical signal from an analog signal transmitted through the first and the second optical filters(113,114). An analog/digital converter(117) converts the analog signals outputted from the first and the second optical detectors(115,116) into digital signals.
    公开号:KR20000060249A
    申请号:KR1019990008384
    申请日:1999-03-12
    公开日:2000-10-16
    发明作者:정윤철；신승균；박근주
    申请人:윤덕용；한국과학기술원；
    IPC主号:
    专利说明:

    A apparatus for monitoring frequency of WDM signals using the pilot tone and two solid etalon filter which have different transmission characteristics}
    BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency monitoring apparatus using an optical filter in a wavelength division multiplexing optical transmission system. In particular, the present invention relates to an optical filter having different transmission characteristics and to each optical signal in order to efficiently maintain and manage the system in a wavelength division multiplexing optical transmission system. The present invention relates to a frequency monitoring apparatus using pilot tone signals of different frequencies.
    A wavelength division multiplexing (WDM) optical transmission system is a system that can greatly increase transmission capacity per optical fiber by multiplexing and transmitting multiple transmission lasers having different wavelengths into one optical fiber.
    In addition, the wavelength division multiplex optical transmission system can greatly increase the transmission capacity per optical fiber even when each laser operates at a relatively low transmission speed. Therefore, it is not necessary to use an optical fiber that is already installed without replacing it with a distributed transition optical fiber. It is possible.
    However, since the multiplexer / demultiplexer for multiplexing / demultiplexing of each channel, which is the most important in the wavelength division multiplex optical transmission system, is sensitive to the frequency of each channel, the output level of each channel is highly related to the performance of the system. In order to operate an optical (WDM) optical transmission system efficiently, the frequency of each channel must be monitored.
    As a conventional technique for monitoring the frequency of an optical signal, a method of measuring the frequency by comparing the ratio of the intensity of the optical signal passing through the two optical filters with the optical filter having two transmission characteristics opposite to each other has been proposed and used.
    However, the conventional method can be used in a single channel system, but optical signals of multiple channels are not applicable to a WDM optical transmission system.
    In addition, as a frequency monitoring method applicable to a conventional WDM optical transmission system, a method for monitoring the frequency of each channel using the channel selection characteristic of an arrayed waveguide grating (AWG), an acoustic optical A method of measuring using an Acousto-Optic Tunable Filter (AOTF) has been proposed.
    However, the conventional method using the AWG has a disadvantage of using an expensive AWG, and in the case of AOTF, since the bandwidth is wider than 1 nm, the frequency and the light output are measured in a system having a channel interval of about 100 GHz. There was a problem that can not be done.
    Accordingly, the present invention has been made to solve the problems of the prior art, two transmission characteristics are already used in the wavelength division multiplex optical transmission system to monitor the presence and size of different optical filters and optical signals. It is an object of the present invention to provide a frequency monitoring device that can efficiently maintain and manage a system by monitoring a frequency of each channel using a pilot tone.
    1 is a configuration diagram of a frequency monitoring apparatus using optical filters having different transmission characteristics according to an embodiment of the present invention.
    2 is a characteristic diagram of an optical filter having different transmission characteristics used in the present invention,
    3 is a configuration diagram of a frequency monitoring apparatus using optical filters having different transmission characteristics according to another exemplary embodiment of the present invention.
    4 is an explanatory view of the operating principle of the present invention,
    5 is a view showing the ratio of the intensity of the pilot tone signal according to the frequency of the optical signal measured using an optical filter having different transmission characteristics used in the present invention,
    6 is an explanatory diagram illustrating a process of extracting a frequency using an inverse function of the graph of FIG. 5,
    Figure 7 is an illustration of the experimental results of measuring the frequency using the present invention.
    Explanation of symbols on the main parts of the drawings
    111, 112: molding combiner 113, 114: optical filter
    115, 116: photodetector 117: analog-to-digital converter
    120: optical frequency extractor 121: high speed Fourier transducer
    122: frequency calculator 201, 202: electrical filter
    203: power detector
    According to the present invention for achieving the object as described above, the optical distribution means for distributing an optical signal including a pilot tone signal input from the outside; A plurality of optical filtering means having different transmission characteristics from each other so as to pass only a constant frequency region of the optical signal distributed by the light distribution means; Light detecting means for converting an output of the optical filtering means into an electrical signal; Provided is a frequency monitoring device comprising an optical frequency extraction means for detecting the intensity of the pilot tone from the output of the optical detection means to measure the frequency of the optical signal.
    Preferably, the optical frequency extraction means, analog digital conversion means for converting the output of the optical detection means into a digital signal; A fast Fourier transformer for performing fast Fourier transform on the digital data converted from the analog to digital conversion means; And an optical frequency calculator for extracting a frequency using the measured pilot tone intensity after measuring the intensity of the pilot tone using the fast Fourier transformed result.
    Preferably, the optical frequency extracting means comprises: a plurality of electrical filtering means for electrically filtering the output of the optical detecting means to output a pilot tone frequency band signal; A plurality of power detectors for measuring the intensity of a pilot tone from the output of said electrical filtering means; And an optical frequency calculator for extracting a frequency using the measured intensity of the pilot tone.
    Preferably, the optical frequency calculator is provided with a frequency monitoring device, characterized in that for measuring the frequency of the optical signal by measuring the ratio of the intensity of the pilot tone using the fast Fourier transformed result.
    Preferably, the optical frequency calculator is provided with a frequency monitoring device, characterized in that for measuring the frequency of the optical signal by measuring the difference in the intensity of the pilot tone using the fast Fourier transformed result.
    Preferably, the optical filtering means is provided with a frequency monitoring device, characterized in that a plurality of optical filters whose transmission characteristics are opposite to each other.
    Preferably, the optical filtering means is provided with a frequency monitoring device, characterized in that the passband characteristic is a solid Fabry-Perot etalon filter having a periodic characteristic according to the wavelength of the optical signal.
    Preferably, the optical filtering means is provided with a frequency monitoring device, characterized in that the passband characteristics are optical fiber Fabry-Perot etalon filter having a periodic characteristic according to the wavelength of the optical signal.
    Preferably, the optical filtering means is provided with a frequency monitoring device, characterized in that the interval between the resonant frequency is a waveguide lattice similar to the channel interval of the wavelength division multiplexed signal.
    Preferably, the optical filtering means is provided with a frequency monitoring device, characterized in that the optical filter capable of filtering in the vicinity of the optical frequency region in which each wavelength-multiplexed optical signal should operate.
    Preferably, the optical filtering means is provided with a frequency monitoring device, characterized in that the plurality of filters whose transmission characteristics are opposite to each other.
    In the following, a preferred embodiment of a frequency monitoring apparatus using optical filters having different transmission characteristics according to the present invention will be described in detail.
    1 is a block diagram of a frequency monitoring apparatus using optical filters having different transmission characteristics according to an embodiment of the present invention.
    As shown in the figure, the frequency monitoring device using an optical filter having different transmission characteristics according to an embodiment of the present invention, the first molded-coupler 111 for extracting an optical signal input from the outside from the optical path, A second shaping coupler 112 for equally distributing and outputting a signal input from the first shaping coupler 111, and a second bandpass filtering for the signal input from the second shaping coupler 112. First and second optical detectors 115 for measuring and outputting the intensity of the optical signal from the analog signals passing through the first and second optical filters 113 and 114 and the first and second optical filters 113 and 114. 116 and an analog-to-digital converter 117 for converting analog signals of the first and second photodetectors 115 and 116 into digital signals, and receiving a digital signal from the analog-digital converter 117 to obtain a frequency. And a frequency extractor 120 for extracting and outputting.
    In addition, the frequency extractor 120 inputs a fast Fourier transformer 121 for performing a fast Fourier transform on a signal input from the analog-digital converter 117, and a Fourier transformed signal from the fast Fourier transformer 121. And a frequency calculator 122 for extracting and outputting the frequency.
    Now, look at the operation of the frequency monitoring device using a filter with different transmission characteristics according to an embodiment of the present invention in detail.
    First, the first shaping coupler 111 extracts and outputs a part of an optical signal including a pilot tone signal allocated to each wavelength input from the outside connected to the optical path, and the second shaping coupler 111 forms the first shaping. The optical signal input from the combiner 111 is distributed and output.
    That is, the first molded coupler 111 is connected to the optical path, 99% of the output of the optical signal is passed through, the remaining 1% is extracted and output, the second molded coupler 112 is the first molded coupler The signal input from 111 is divided equally and output by 50:50.
    In addition, the first optical filter 113 and the second optical filter 114 display different transmission characteristics, and are equally distributed and output the filtered signal.
    Preferably, the first optical filter 113 and the second optical filter 114 may be composed of two optical filters whose transmission characteristics are opposite to each other.
    In addition, preferably, the first optical filter 113 and the second optical filter 114 may be configured as a solid Fabry-Perot etalon filter whose passband characteristics are periodic according to the wavelength of the optical signal. .
    In addition, preferably, the first optical filter 113 and the second optical filter 114 may be configured of an optical fiber Fabry-Perot etalon filter having a passband characteristic having a periodic characteristic according to the wavelength of the optical signal. .
    In addition, preferably, the first optical filter 113 and the second optical filter 114 may be configured as waveguide gratings having a distance between the resonant frequencies similar to the channel spacing of the wavelength-multiplexed signal.
    In addition, preferably, the first optical filter 113 and the second optical filter 114 may be configured as optical filters capable of filtering in the vicinity of an optical frequency region in which each of the wavelength division multiplexed optical signals should operate.
    2 is a characteristic diagram of optical filters having different transmission characteristics used in the present invention, and shows transmission characteristics of an etalon filter in which transmission characteristics of two optical filters are opposite to each other.
    That is, the frequency where the transmission is best in the first optical filter is the same as the frequency where transmission is least in the second optical filter.
    Therefore, as the size of the optical signal passing through the first optical filter and the second optical filter is changed according to the frequency of the optical signal and the size of the optical signal is reduced, the size of the pilot tone is also reduced.
    At this time, the etalon filter can be manufactured by coating both sides of the quartz glass, and the etalon filter changes its properties as the temperature changes, so that the temperature of the etalon filter is kept constant and a thermoelectric cooler and thermistor ( temperature control by means of thermistor.
    Meanwhile, in FIG. 1, the first photodetector 115 and the second photodetector 116 measure the intensity of the optical signal input from the first optical filter 113 and the second optical filter 114, and then measure the intensity of the optical signal. Outputs an electrical signal in accordance with the intensity of the optical signal.
    The analog-to-digital converter 117 receives an analog signal, converts it into a digital signal, and outputs it. The frequency extractor 120 receives a digitally converted signal and extracts and outputs a frequency.
    That is, after the frequency extractor 120 performs the fast Fourier transform on the digital signal input using the fast Fourier transformer 121, the frequency calculator 122 receives the result value of the fast Fourier transform and receives the pilot tone. Measure the optical power of the optical signal according to the measured optical power.
    Meanwhile, the frequency calculator 122 receives the result value of the fast Fourier transform, measures the power of the pilot tone, and measures the frequency of the optical signal using the measured power difference, or uses the ratio of the measured power. The frequency of the optical signal can be measured.
    3 is a block diagram of a frequency monitoring apparatus using optical filters having different transmission characteristics according to another embodiment of the present invention.
    As shown in the figure, the frequency monitoring device using an optical filter having different transmission characteristics according to another embodiment of the present invention, the first molded-coupler 111 for extracting an optical signal input from the outside from the optical path, A second shaping coupler 112 for equally distributing and outputting a signal input from the first shaping coupler 111, and a second bandpass filtering for the signal input from the second shaping coupler 112. First and second optical detectors 115 and 116 for detecting and outputting the intensity of the optical signal passing through the first and second optical filters 113 and 114 and the first and second optical filters 113 and 114. A plurality of electrical filters 201 and 202 for performing electrical filtering to extract only components of a pilot tone frequency from signals passing through the first and second photo detectors 115 and 116, and the plurality of electrical filters ( Signal passed through 201, 202 From using the strength of a pilot tone power detector 203 and the measurement for measuring the strength of a pilot tone and a frequency calculator (122) for extracting frequency.
    Now, operation of the frequency monitoring device using a filter having different transmission characteristics according to another embodiment of the present invention will be described in detail.
    According to another embodiment of the present invention, during operation of a frequency monitoring device using a filter having different transmission characteristics, the first molded-coupler 111 and the first molded-coupler (for extracting an optical signal input from the outside from the optical path) A second shaping coupler 112 for equally distributing and outputting a signal input from 111, and first and second optics for performing different bandpass filtering on the signal input from the second shaping coupler 112. The operation of the first and second photo detectors 115 and 116 for detecting and outputting the intensity of the optical signal passing through the filters 113 and 114 and the first and second optical filters 113 and 114 is illustrated in FIG. As described in 1.
    The plurality of electrical filters 201 and 202 filter the output signals of the first and second photodetectors 115 and 116 to pass only a pilot tone frequency, and the power detector 203 Pilot tone intensities are measured and output at the outputs of the plurality of electrical filters 201 and 202.
    The frequency calculator 122 measures and outputs a frequency using the measured intensity of the pilot tone.
    Meanwhile, the frequency calculator 120 may measure the frequency using the measured ratio of the intensity of the pilot tone, or may measure the frequency using the difference of the intensity of the pilot tone.
    4 is an explanatory diagram of the operating principle of the present invention.
    As shown in the figure, when the optical signal passing through the optical filter 113, 114 having the mutually opposite transmission characteristics, the transmission characteristics of the filter vary depending on the frequency, so that when the optical signals are in positions A, B, C, and D, respectively, The magnitude of the signal passing through the filter varies.
    At this time, if the intensity of the signal passing through the first optical filter 113 is different from the intensity of the signal passing through the second optical filter 114, it can be known at which frequency, such as A, B, C, D, etc. Will be.
    However, when only the intensity of the optical signal is detected, the pilot tone is used because the frequencies of several optical signals cannot be detected at the same time.
    When the intensity of the optical signal passing through the first optical filter 113 and the second optical filter 114 is changed, the intensity of the pilot tone carried on the optical signal is also changed, so that the analog signal is converted into a digital signal and the fast Fourier transform is performed. After detecting the intensity of the pilot tone, information on the frequency of the optical signal can be obtained.
    In addition, when the etalon filter is used, the first optical filter 113 and the second optical filter 114 have the same characteristics periodically, so that they can be applied to optical signals having different optical frequencies for each period. Since the frequency of the optical signal can be measured, the present invention can be applied to a wavelength division multiplex transmission system.
    Here the measurable frequency range is half the period of the etalon filter.
    That is, if the period of the etalon filter is 100 Hz, the range of the frequency that can be monitored is 50 Hz, which is half the period of the optical filter.
    5 is a diagram showing the ratio of the intensity of the pilot tone signal to the frequency of the optical signal measured using an optical filter having different transmission characteristics used in the present invention, wherein the frequency of the optical signal to which the pilot tone is applied The ratio of the intensity of the optical signal passing through the optical filter was measured by comparing the intensity of the pilot tone with varying from 193.14 Hz to 193.06 Hz.
    At this time, it can be seen that a 1-to-1 relationship between the ratio of the intensity of the pilot tone and the frequency of the optical signal is established from 193.08 kHz to 193.13 kHz.
    6 is an explanatory diagram illustrating a process of extracting a frequency of an optical signal using an inverse function of the graph of FIG. 5, and represents an inverse function obtained from the measured value of FIG. 5.
    Therefore, the frequency of the input optical signal can be obtained by knowing the ratio of the intensity of the measured pilot tone.
    At this time, the frequency of the optical signal can be calculated from the ratio of the intensity of the pilot tone by using the following simple equation (Equation 1).
    Where F is the frequency THz of the optical signal and P is the intensity of the pilot tone.
    In the drawings, Figure 7 is an exemplary view of the experimental results of measuring the frequency of the optical signal using the present invention, showing the error of the frequency of the optical signal measured by the frequency monitoring device and the frequency measured by the optical frequency meter.
    7 shows that the measurement can be performed within an error of ± 1 dB for an input change of -15 dBm to -25 dBm within a range of 50 Hz.
    As described in detail above, the frequency monitoring apparatus using the optical filter having different transmission characteristics of the present invention uses an etalon filter having transmission characteristics opposite to that of the pilot tone in the wavelength division multiplex optical transmission system to adjust the frequency of each optical signal. At the same time, there is no dynamic part, and since it is possible to measure the exact frequency with a simple algorithm, it is economical to monitor the frequency of the split-multiplex optical transmission system.
    The technical idea of the frequency monitoring device using the optical filter having different transmission characteristics of the present invention has been described above with the accompanying drawings, but this is by way of example only and not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.
    权利要求:
    Claims (12)
    [1" claim-type="Currently amended] Optical distribution means for distributing an optical signal including a pilot tone signal input from the outside;
    A plurality of optical filtering means having different transmission characteristics from each other so as to pass only a constant frequency region of the optical signal distributed by the light distribution means;
    Light detecting means for converting the output of the optical filtering means into an electrical signal; And
    And an optical frequency extraction means for detecting the intensity of the pilot tone from the output of the optical detection means and measuring the frequency.
    [2" claim-type="Currently amended] The method of claim 1,
    The optical frequency extraction means,
    Analog to digital conversion means for converting the output of the light detecting means into a digital signal;
    A fast Fourier transformer for performing fast Fourier transform on the digital data converted from the analog to digital conversion means; And
    And an optical frequency calculator for extracting a frequency using the measured intensity of the pilot tone after measuring the intensity of the pilot tone using the fast Fourier transformed result.
    [3" claim-type="Currently amended] The method of claim 1,
    The optical frequency extraction means,
    A plurality of electrical filtering means for electrically filtering an output of the light detecting means to output only a frequency of a pilot tone;
    A power detector for detecting the intensity of the pilot tone from the output of the electrical filtering means; And
    And an optical frequency calculator for extracting a frequency using the measured intensity of the pilot tone.
    [4" claim-type="Currently amended] The method of claim 2 or 3,
    The optical frequency calculator,
    And extracting a frequency by using the ratio of the measured intensity of pilot tones.
    [5" claim-type="Currently amended] The method of claim 2 or 3,
    The optical frequency calculator,
    A frequency monitoring device, characterized in that the frequency is extracted by using the difference of the intensity of the measured pilot tone.
    [6" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    A frequency monitoring device, characterized in that the plurality of filters having mutually opposite transmission characteristics.
    [7" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    A frequency monitoring device, wherein the passband characteristic is a solid Fabry-Perot etalon filter having periodic characteristics depending on the wavelength of the optical signal.
    [8" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    A frequency monitoring device, wherein the passband characteristic is an optical fiber Fabry-Perot etalon filter having periodic characteristics depending on the wavelength of the optical signal.
    [9" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    And a waveguide lattice in which the interval between the resonance frequencies is similar to the channel interval of the wavelength division multiplexed signal.
    [10" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    And an optical filter capable of filtering in the vicinity of an optical frequency region in which each wavelength-multiplexed optical signal should operate.
    [11" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    A frequency monitoring device, characterized in that the plurality of filters having mutually opposite transmission characteristics.
    [12" claim-type="Currently amended] The method according to any one of claims 1 to 3,
    The optical filtering means,
    A frequency monitoring device, characterized in that the plurality of filters having mutually opposite transmission characteristics.
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    同族专利:
    公开号 | 公开日
    KR100292808B1|2001-06-15|
    US6548806B1|2003-04-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1999-03-12|Application filed by 윤덕용, 한국과학기술원
    1999-03-12|Priority to KR1019990008384A
    2000-10-16|Publication of KR20000060249A
    2001-06-15|Application granted
    2001-06-15|Publication of KR100292808B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019990008384A|KR100292808B1|1999-03-12|1999-03-12|A apparatus for monitoring frequency of WDM signals using the pilot tone and two solid etalon filter which have different transmission characteristics|
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