• 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:
    The present invention relates to an optical transmitter with dual phase and amplitude modulation generated by two respective electrical signals consisting of synchronous pulses that directly modulate a laser and an electro-absorption modulator, integrated monolithically, producing an optical signal modulated in phase and amplitude respectively. The technique generates a multilevel impulse signal that indicates phase changes through positive or negative pulses of variable duty cycle. The amplitude modulation of residual intensity of the laser is corrected by a subtractor branch to the EAM. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2695901A1
    申请号:ES201730902
    申请日:2017-07-06
    公开日:2019-01-11
    发明作者:Gomà Josep Prat
    申请人:Universitat Politecnica de Catalunya UPC；
    IPC主号:
    专利说明:

    [0001]
    [0002]
    [0003]
    [0004] SECTOR OF THE TECHNIQUE
    [0005]
    [0006] The invention is part of the technical sector of broadband telecommunications with an emphasis on local fiber optic access networks.
    [0007]
    [0008] BACKGROUND OF THE INVENTION
    [0009]
    [0010] Fiber-optic networks by ultra-dense multiplexing of wavelengths are being considered as an option to improve the capacity of optical access networks [1]. Although wavelength multiplexing and coherent detection are already common in long-distance optical communications, their use in access networks has been limited by the cost of the devices and the complexity of the processing. In particular, the coherent transmitter generally modulates the optical phase and requires an external modulator that makes the terminals of the users more expensive. For its part, the coherent receiver, whether homodyne or heterodyne, uses a laser as an optical local oscillator that mixes with the data signal.
    [0011]
    [0012] In order to use a simple transmitter, direct modulation of laser intensity is generally used in access networks. However, this generates a widening of the optical spectrum due to the intrinsic modulation of the laser frequency ("chirp"), which is excessive for a dense multiplexing in wavelength. To minimize this, lasers with managed chirp (CML) based on interferometers or distributed feedback filters have been proposed [2]; however, the CML requires a very critical optical spectrum configurator coupled to the laser. In the past, direct phase modulation of a laser was also proposed previously by deriving the electrical data signal using its adiabatic frequency chirp [3]. Recently this was demonstrated, preequalizing directly at high-pass to the laser input [4], without requiring a phase modulator external to the laser as usual and obtaining compact optical spectra without optical filtering; it has also been proposed and demonstrated the direct modulation of phase by means of a multilevel signal consisting of digital pulses with a short work cycle to directly modulate the laser digitally [5,6]. The bandwidth of this modulation can be extended to high frequencies thanks to the transient chirp of the laser or a resonance in the cavity.
    [0013]
    [0014] On the other hand, lasers can be manufactured with monolithically integrated modulators both in the same photonic circuit with III-V materials. This modulating section is usually of the Electro-Absorption (EAM) type, giving rise to the EML type transmitters ("ElectroAbsortion Modulated Laser"). This modulation uses the Franz-Keldish effect of ultrafast modulation of the intensity of the light by electric field. , with a very low chirp. [7] There are also modulators of the Mach-Zehnder or IQ interferometric type, which give rise to the IML type transmitters.The latter allow to obtain, modulating several sections of the interferometer / s, complex multilevel modulations of the type QAM, required in the most modern systems of fiber optic broadband communications with coherent optical reception, however, they are more complex than EAM, both in terms of photonic integration and electronic radio-frequency injection in the multiple electrodes, and when introducing greater optical losses usually require optical amplifier.
    [0015]
    [0016] The present innovation combines the mentioned technique of direct modulation of the laser in phase with digital impulses and of the amplitude modulation by electro-absorption in a same device, and extends them to generate complex multilevel modulations of the QAM type, but with a much lower complexity to the IML. For this, both sections, laser and electro-absorption, must be synchronized and pre-encoded in addition. The electro-absorption section is unable to modulate the optical phase substantially, while the laser section is unable to modulate its amplitude efficiently, but its phase by applying the referred procedures. In this way both integrated sections can be supplemented to modulate both orthogonal variables of the light synchronously, amplitude and phase, and thus generate QAM or the required complex equivalent low-pass constellation. The photonic integrated circuit can also integrate an amplifier section, which has modulation characteristics similar to those of the laser.
    [0017]
    [0018] As can be inferred from the following description, the proposed device and method can be applied industrially with the existing technological processes, by the broadband telecommunications equipment manufacturers, in order to increase the capacity and / or reduce the costs of the current optical communications.
    [0019] Bibliography
    [0020]
    [0021] [1] J. Prat, et al., "Technologies for Cost-Effective udWDM-PONs," Journal of Lightwave Technology, vol. 34, no.2, 2016.
    [0022] [2] Y. Matsui, et al., "Chirp-managed directly modulated laser (CML)," in IEEE Photon. Technol. Lett., Vol. 18, no.2, pp. 385-387, January 2006.
    [0023] [3] RS Vodhanel; AF Elrefaie; MZ Iqbal; RE Wagner; JL Gimlett; S. TsujiJ, "Performance of directly modulated DFB lasers in 10-Gb / s ASK, FSK, and DPSK lightwave systems", J. of Lightwave Technology, vol. 8, no.9, pp. 1379-1386, 09-1990.
    [0024] [4] IN Cano, A. Lerin, V. Polo, J. Prat, "Direct phase modulation DFB for cost-effective ONU transmitter in udWDM-PONs," in IEEE Photonics Technology Lett., Vol. 26, no. 10, pp. 973-975, 05-2014.
    [0025] [5] National Patent Application n. 201631206 to 09-16-2016, "Method of direct modulation of the optical phase of a laser by means of an encoded pulse signal and variable work cycle", I. Cano, J. Prat.
    [0026] [6] J. C. Velásquez, Iván. N. Cano, V. Polo, J. Prat, "Direct Beat Phase Modulated DFB for flexible 1.25-5 Gb / s Coherent UDWDM-PONs", OFC-2017, Los Angeles, paper Th2A.32, 03-2017.
    [0027] [7] G. Chu, I. Cano, V. Polo, J. Prat, "Application on Minimizing Residual AM in DPSK UDWDM-PON ONU by Integrated Dual-EML", IEEE Photonics Journal, vol. 8, no. 3, 08-2016.
    [0028] [8] J. Proakis, Digital communication systems, 2nd ed., New Jersey: Prentice-Hall, 2002.
    [0029] [9] I. N. Cano; Lerín, A .; Presi, M .; Polo, V .; Ciaramella, E .; Prat, J., "6.25Gb / s Differential Duobinary Transmission in 2GHz BW Limited Direct Phase Modulated DFB for udWDM-PONs", ECOC'2014, P.7.2, Cannes, France, 2014.
    [0030] [10] I.N. Spout ; J. Camilo Velásquez; Victor Polo; Josep Prat, "10 Gbit / s Phase Time Diversity Directly Modulated DFB with Single-PD Intradyne Receiver for Coherent WDM-PON", ECOC-2016, W.4.P1, Düsseldorf, Germany, 2016.
    [0031] [11] G.Y.Chu, V. Polo, A. Lerin, J. Tabares, I.N.Cano, J. Prat, "1.25-3.125 Gb / s per user PON with RSOA as phase modulator for statistical wavelength ONU" Optics Communications, Vol.
    [0032] 357, pp.34-40, 2015.
    [0033] [12] Iván N. Cano, F. Bottoni, J.C. Velásquez, Marco Presi, E. Ciaramella, J.Prat, "Bidirectional Coherent PON with UN Based on Reused Direct-Modulated LO", OFC-2016, Anaheim, USA, M3C.7.
    [0034] [13] GYChu, INCano, V. Polo, C. Kazmierski, R. Brenot, J. Prat, "Monolithically Integrated Dual-Output DEML for Full Duplex DPSK-ASK and DPSK-SSB ONU in Ultra-Dense Channel Spaced Access Network" , IEEE / OSA, Journal of Lightwave Technology (JLT), vol.34, no.8, 15 April, 2016 [14] PCT patent application P200700765, "Wavelength Shifter Module for Optical Fiber Access Communications", J.Prat.
    [0035] EXPLANATION OF THE INVENTION
    [0036]
    [0037] The present invention provides a method for generating an optical signal modulated in phase and in amplitude from the direct modulation of a laser and a monolithically integrated electro-absorption modulator in the semiconductor chip. The laser section is injected with a multilevel pulsed data signal, corresponding to the phase variations of the constellation with respect to the previous symbol, in the form of pulses with variable duty cycle of maximum one symbol time and, simultaneously, a signal is injected. multilevel data signal to the electro-absorption modulator section corresponding to the amplitude levels of the constellation symbol module.
    [0038]
    [0039] First of all, in the transmitter, the data signal is introduced to a multilevel complex mapper or encoder that corresponds several bits of the digital input information in a symbol or baud, now defined by the two signals, of variation in phase and amplitude. , towards the laser and the modulator respectively; this is an alternative to conventional systems, in which the complex modulation is determined by two orthogonal signals, one in-phase (I) and another in-square (Q), modulating Mach-Zehnder modulators that are then combined in a coupler, previous optical delay of one of them of 90 degrees.
    [0040]
    [0041] The phase pulse signal is obtained in a pulse encoder by differentiating or subtracting the signal with itself delayed in a short time, generally much lower than the symbol time, thus operating as a flank detector; pulses other than the central value will represent proportional changes in the optical phase, producing a positive pulse of optical frequency on a positive flank and a negative pulse on a negative flank. In this way, a phase variation corresponding to the input signal to the pulse generator is obtained at the laser output, limited by the integration time corresponding to the delay of the pulse encoder. For the amplitude, the pulses of the second output of the mapper represent the discrete levels of the module of each symbol in the constellation.
    [0042]
    [0043] Usually the multi-level pulse signal will be adapted, equalized and amplified, so that, by directly modulating a laser, it produces the desired changes in the optical phase (for example of multiples of 90 degrees or odd multiples of 45 degrees in QPSK, according to the orientation of the constellation), thanks to the "chirp" phenomenon of the semiconductor laser. The EAM section has a faster and simpler dynamic, which means that it requires a substantial adaptation.
    [0044]
    [0045] In practical lasers it happens that in direct modulation of the injection current to the laser both modulations are produced simultaneously, of frequency (phase) and amplitude; therefore the separation between phase modulation and amplitude is not exact, but there is a partial mixture. By injecting the data signal to the laser according to the modulation of the desired phase, we have the residual intrinsic intensity modulation, usually 1 or 2 dB of amplitude variation, according to its chirp parameter. In binary modulation of two phase levels this does not suppose a serious problem, but with the multilevel modulation that inter-relation is very adverse. As we demonstrated in [7], this effect can be compensated through the properly controlled electro-absorption section. A sample of the phase signal is inverted and added to the amplitude signal to the EAM. With this correction, the independence between the two coding branches (phase and amplitude) is achieved.
    [0046]
    [0047] A differential demodulator, which compares the phase with the phase of the previous symbol, is advantageously used in the receiver, since it is simpler and more tolerant to the phase noise of the lasers than the synchronous receivers. You can also use a previous synchronous receiver for accurate estimation of the optical phase. According to this choice, a differential precoder will be used in the transmitter or not. The receiver simultaneously also detects the amplitude of each symbol so that, together with the detected phase, it obtains the corresponding transmitted digital symbol in a multilevel decoder or demapping device.
    [0048]
    [0049] Thus, the design of the transmitter is the main object of the present invention, the general object of the invention being an optical communication system, which transmits data modulated according to the proposed method, and which consists of:
    [0050] a) A transmitter based on a single-mode laser, whose phase is directly modulated, integrated monolithically with an electro-absorption modulator that modulates the amplitude of the optical field. The transmitter includes a pulse generator pre-encoder that transforms the original data signal into a multilevel pulse signal, differentially encoded in preference, and an adapter block to the two sections of the photonic device.
    [0051] b) An optical transmission link
    [0052] c) A receiver preferably based on coherent detection, which uses a laser as an optical local oscillator that tunes the desired optical channel, in a manner equivalent to a heterodyne radio receiver. It contains a demodulator, a decoder, and a chromatic dispersion compensator when required. It can also include a radio frequency stage to lower the baseband signal and one or more stages of equalization and filtering to reduce noise and distortion of the signal.
    [0053]
    [0054] There is another possible relevant version of the device that can be contemplated in the invention, since it is capable of performing the same function. Usually the optical interfaces or transceivers contain a transmitter and a receiver, to establish a bidirectional communication. As indicated, coherent receivers require a laser, unlike conventional direct detection, which acts as a local oscillator that tunes the desired optical channel, equivalent to a heterodyne radio receiver. To avoid this extra laser, it is possible to share the transmitter's laser, under certain conditions, as has been proven in [11, 12]. In the case of the proposed device, with laser in phase modulation, this is not appropriate since the modulation of the laser does not offer a pure signal as required by the local oscillator.
    [0055]
    [0056] To solve it, a solution is proposed, which also forms an integral part of the invention, although in separate terms. It consists of adding a third section of semiconductor optical amplifier (SOA) to the optical device, following the EAM, and, at the same time, establishing two optical outputs: one on the side of the laser section and one on the SOA side. The first is not modulated and serves as the local oscillator of the receiver, while the second is modulated in amplitude and phase, constituting the transmitter output. Now the phase modulation is not done by the laser, but by the SOA. Both are based on the same semiconductor materials and have very similar dynamic and chirp characteristics. The fundamental difference is that the laser is bounded by two reflectors while in the SOA it is not. This implies that the adiabatic chirp modulation of the laser is in frequency while that of the SOA is directly in phase [11,13]. The scheme of the transmitter is thus the same except for the pulse encoder, which is now not used. This configuration is also novel; there is no known dual phase and amplitude modulation with this configuration of the device, nor with dual optical output for the two functions.
    [0057]
    [0058] Other advantages of the integration of an SOA section is that it allows to increase the transmission power compensated for the losses imposed by the EAM, of several decibels. Another advantage is that of being able to act as a light switch, for example while the laser is retuned avoiding interference to other channels. Also the SOA together with the EAM it can perform wavelength shifting functions to avoid Rayleys backscattering, as described in [14].
    [0059]
    [0060] BRIEF DESCRIPTION OF THE DRAWINGS
    [0061]
    [0062] To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, an illustrative and non-limiting set of drawings is attached as an integral part of said description.
    [0063]
    [0064] Figure 1 shows a block diagram of the transmission system detailing the optical transmitter (100) object of the invention.
    [0065]
    [0066] Figure 2 shows the block diagram of the pulse encoder for generating the multilevel short pulse signal. It is composed of a subtracter that subtracts the value of the signal from the same signal delayed by a time Ti through a delay element that will be at most equal to a symbol time and that will define the work cycle of the pulses. In dotted lines, the signal is drawn to the EAM, correcting the residual intensity modulation of the laser.
    [0067]
    [0068] Figure 3 shows an example of multilevel input signals to the laser section and data to the modulator section EAM.
    [0069]
    [0070] Figure 4 shows an example of a constellation of 8 levels (3 bits) and of 16 QAM levels (4 bits), with the corresponding phases and amplitudes.
    [0071]
    [0072] Figure 5 shows the optical device with the Laser, EAM and SOA sections, with an extra laser output to the receiver.
    [0073]
    [0074] PREFERRED EMBODIMENT OF THE INVENTION
    [0075]
    [0076] The preferred implementation of the optical transmitter (TX, 100) is shown in Figure 1, there being variants that are obviously derived from it. Its design is configured as a series of connected blocks that are described below, as well as its working together:
    [0077]
    [0078] In the transmitter, some stages of analog-digital electrical processing that generate two signals of multilevel pulses, one for the phase and another for the amplitude, from the digital input information, which directly modulate the laser and the EAM section respectively, to obtain an optical signal modulated in phase and in amplitude simultaneously, which is subdivided into the following blocks as shown in Figure 1:
    [0079]
    [0080] • A Multilevel Complex Mapper (MAP, 101) with one digital input and two pulsed outputs. Matches blocks of m bits of the digital input information in a digital symbol in each defined baud two values without return to zero: one of the phase (O) and the other of the amplitude (A) of the symbol, which come out to the laser sections and EAM respectively. This block can be implemented preferably with a table in memory ("look-up table") with the two values in the memory position directly accessed with the m bits of the symbol.
    [0081]
    [0082] • A differential precoder (PRE, 102) that generates a replica of the signal towards the laser without return to zero but differentially coded; it is constituted by an analog or digital subtracter implemented with an M-module subtractor or with an XNOR logic gate, whose inputs will be:
    [0083] o The phase output data signal (O) of the Mapper.
    [0084] o The feedback signal of the encoder output delayed a symbol time (Ts).
    [0085] This block may not be essential depending on the implementation of the rest of the transmitter and receiver blocks.
    [0086]
    [0087] • A pulse encoder (COD, 103) that generates a multilevel pulse signal to the laser section with a duty cycle of maximum one bit time. This encoder acts as a flank detector that produces a short positive pulse when there is a positive flank (transition from less to more), and a negative pulse when there is a negative flank (transition from plus to minus); the amplitude of the generated impulses are proportional to the input. This encoder can be implemented with an analog subtractor with the following inputs:
    [0088] o The previous data signal (O) coded.
    [0089] o The same signal but with a delay Ti that can be variable of how maximum of a symbol time, and that will define the work cycle of the impulses.
    [0090]
    [0091] In the example of Figure 3 this pulse signal is shown with a duty cycle of half a symbol time Ti = Ts / 2 for the constellation example 2xQPSK of Figure 4; the outer circle has 4 symmetric levels plus zero; the inner circle can be mapped with 5 levels, or with 4 levels if the central value is moved. This produces a multilevel pulse signal that indicates changes in the optical phase of the signal. The zero reference level of this pulse signal indicates that there is no change in the optical phase, while the positive and negative values (taking as reference the central value) produces positive and negative changes respectively in the optical phase of the modulated signal. These pulse values are adjusted so that their temporal integral multiplied by the "chirp" factor of the laser offers the desired phase variation in each symbol with respect to that of the previous symbol. Synchronously, the amplitude signal to the EAM has two possible values here, corresponding to the radii of the two circles, inner and outer; it thus carries a bit of information. The example of the 16QAM constellation is also shown in Figure 4 (right): here there are 3 amplitude and 12 phase values, plus the reference value that can match one of the 12.
    [0092]
    [0093] The two respective signals to the laser + EAM photonic device will be adapted to the device according to its physical opto-electronic parameters by means of an Adapter module (Ad, 105), located as close as possible to the device to extend the broadband and adapt impedances, to the instead of equalizing the delays of the two branches (A and O). The pulse signal directly modulates the laser section. To better adapt the impedances, one resistor can be placed in series with the laser and another one in parallel with the EAM, while the DC bias is introduced to both (from tens of mA to the laser and from a few volts from cathode to anode). of the EAM). The amplitude level signal attacks the EAM section preferably by subtracting a small portion of the phase signal to compensate for the residual intensity modulation of the laser. Thus, this module conditions the two signals, amplifying them, equalizing them to adjust their bandwidth and compensating the residual intensity modulation of the laser by the EAM. To implement this last function, this transmitter module adds a branch with an attenuator (or with an amplifier if the signal has been excessively attenuated) from the phase signal to the laser to a subtracter to the input of the EAM, proportional to the signal to the laser, according to its chirp parameter, in such a way that the amplitude remains constant when only the phase is modulated. It is easily adjustable, in design or in production: modulating only the phase (O), measuring the instantaneous power at the output of the photonic device by means of a simple fast photo-detector and a wide-band oscilloscope, and varying the gain of the crossed branch ( from O to A, according to Figure 1) until the signal in the oscilloscope remains constant (at least in average value within each symbol). Thus, the amplitude or envelope of the optical signal will be only proportional to the amplitude signal (A), precisely.
    [0094]
    [0095] The photonic device is basically a monomode semiconductor laser integrated with a section of electro-absorption (EAM) monolithically, as has been mentioned, with separate broadband electrodes for signal injection and polarization to the two sections. The laser is typically of the type DFB (Distributed-FeedBack), DBR (Distributed-Back-Reflector) or variants thereof. The EAM section uses the Franz-Keldish effect of ultra-fast intensity modulation. Using a DFB-type laser, the wavelength tuning is thermally limited to a few nanometers, but by combining the multiple transmitters of the network according to the methodology described in [1], the practical total occupancy of a broad band of the optical spectrum is achieved with high spectral efficiency.
    [0096]
    [0097] The preferred transmission medium is the standardized single-mode optical fiber, in a point-to-multi-point topology like the PON networks typical of the FTTH (Fiber-to-the-Home) access networks. It is not necessary to make modifications to the external fiber optic cable distribution plant, since the proposed system has a higher power margin and fits into a narrow spectrum.
    [0098]
    [0099] The receiver will preferably be coherent, with a local oscillator laser that will be tuned to the wavelength of the desired channel with the signal generated in phase and amplitude, for homodyne or heterodyne detection. The receiver contains a differential demodulator for the phase that will be responsible for comparing the difference in the phases of two consecutive symbols, and a chromatic dispersion compensator when required. It may also include a radio frequency stage to lower the baseband signal and one or more stages of equalization and filtering to reduce the added distortion and noise in the transmission channel.
    [0100]
    [0101] The second preferred implementation modifies the photonic device by adding a section of semiconductor optical amplifier (SOA, 201) and now coupling two light outputs, as shown in Figure 5: one output as a transmitter on the SOA side, and another output as the local oscillator of the receiver of the same transceiver (RX, 202) on the To be. The phase modulation performed by the laser is now performed by the SOA; the laser is simply polarized without modulation. This change of function allows to share the unique photonic device between the transmitter and the receiver, saving costs and simplifying the management of wavelengths. The block diagram of the transmitter is the same except for the Pulse Encoder (Cod 103), which is no longer necessary because the SOA modulates the optical phase directly, and provides an extra optical output to the receiver (RX 202), as a local oscillator signal to be mixed with the received optical signal. The presence of a differential decoder will also depend on whether the receiver demodulator is synchronous or differential.
    [0102]
    [0103] As is evident, alternatively the laser could be separated from the chip, and connected to the EAM + SOA modulator chip for example through a waveguide on a Silicon substrate, still losing density.
    [0104]
    [0105] Although the description given corresponds to two preferred implementations, an expert can make implementable variations of them following the fundamental idea of the invention, with the architecture and methodology defined.
    [0106]
    [0107] In an equivalent alternative implementation, the defined functions of the blocks Prec (102), Cod (103) and Ad (104) can for example be incorporated into the block Map (101) or another similar one, in such a way that the functions defined would be done with digital numerical processing, which would convert the two analog signals to the photonic device by means of two Digital-Analog converters (DAC).
    [0108]
    [0109] A possible specific case is when the delay time of the pulse encoder block (COD, 103) is equal to or of the symbol time order. In this case, the impulses are as wide as the symbol and thus the bandwidth of the signal is reduced, although at the risk of causing intersymbolic interference due to the overlap of the data, and then the decision time must be fine-tuned at the end of each symbol . In this case, the PREC and COD blocks do complementary functions and can be redundant, generating a continuous phase modulated signal of MSK (Minimum Shift Keying) or CPFSK (Continuous Phase Frequency Shift Keying) since the phase variations of the laser are continuous , with the same type of reception detection, similar to the DPSK or DQPSK [8].
    [0110]
    [0111] In the preferred embodiment, the consecutive symbols are independent of each other. However, having correlation between them may be desirable to extend the speed of transmission beyond the bandwidth of the system. This naturally leads to a coding of the duobinary type. As demonstrated in [9], duobinary coding can also be applied to the phase by taking advantage of the 360 ° cyclicity in the constellation argument, and increasing the excursion of the current injection. This form of transmission would basically consist of the same scheme defined by adapting the Mapping block, according to [9].
    [0112]
    [0113] In another possible implementation, the COD block (103) can be made analogically with a high-pass bypass filter, which approximates the difference function defined in the COD block.
    [0114]
    [0115] For further simplification of the transmitter and receiver electronics, the phase and amplitude data signal can be decoupled and independently detected with a phase detector branch and another separate amplitude detector, avoiding synchronism, at the cost of losing sensitivity and reach.
    [0116]
    [0117] For the sake of simplifying the homodyne receiver, in number of photodetection branches mainly, the technique of phase shaping or phase mixing demonstrated in [10] can be applied here, whereby the constellation is rotated by 90 ° in half of each symbol. In this way it is possible to avoid bending the photodetection branches (one for the component in phase (I) and another one for the quadrature component (Q)), and use it to demodulate the two components with the same phototection branch and demodulation, but in two different instants, in each half of the symbol. To implement it in the part of the transmitter, which is the object of the invention, the Symbol Mapper must add 90 ° in its phase output (O) in the second half of the cycle.
    权利要求:
    Claims (5)
    [1]
    1. Optical transmitter with dual phase modulation and coherent light amplitude through two encoded pulse signals comprising:
    • a photonic integrated active device with a monomode laser and a monolithically integrated electro-absorption modulator (EAM),
    • an amplitude-phase complex digital mapping encoder,
    • a differential precoder,
    • a multi-level pulse encoder of the phase signal and
    • a block Signal adapter that adjusts the levels and corrects the modulation of residual intensity of the laser through the EAM,
    and characterized in that both photonic elements, laser and EAM, are modulated directly with the respective phase and module combinations of each symbol in the complex constellation QAM, from the digital information to be transmitted, by means of:
    to. a signal of direct electric current to the laser consisting of discrete pulses of impulsive type of several levels and with a short work cycle, of maximum one period of symbol in the different levels of "0" (reference central value), and that produces a optical signal whose optical phase is modulated in such a way that:
    • the state "0" represents that there is no change in the optical phase while • the other levels indicate positive or negative changes in the optical phase according to the amplitude of the pulse, which is adjusted so that its temporal integral multiplied by the factor of "chirp" of the laser offer the desired phase variation in each symbol with respect to that of the previous symbol in the constellation.
    b. an electrical voltage signal to the EAM corresponding to the amplitude or modulus of the QAM symbol to be transmitted, to which a sample of the laser injection current signal is subtracted, to compensate for the residual intensity modulation in the laser.
    [2]
    The method according to Claim 1 wherein the shape of the phase pulses in the transceiver can be formed by an equalizer or analog high pass filter, which approximates the function of the multilevel pulse encoder.
    [3]
    3. The method according to claim 1 or 2 wherein the pulse width of the laser pulse signal is equal to or in the order of the symbol time and in this case the PREC and COD blocks are redundant and are obviated, generating the signal wave modulated in continuous phase of the MSK type (Minimum Shift Keying) or CPFSK (Continuous Phase Frequency Shift Keying), with the same type of detection in reception as DPSK.
    [4]
    4. Optical transmitter with dual phase modulation and coherent light amplitude through two encoded pulse signals comprising:
    • an active photonic integrated device with a monomode laser, an electro-absorption modulator (EAM) and a semiconductor optical amplifier (SOA) integrated monolithically, and with two light outputs:
    i. one on the side of the unmodulated laser, towards the Receiver, and
    ii. another on the SOA side, modulated to the Transmitter output,
    • an amplitude-phase complex digital mapping encoder,
    • a differential precoder, depending on the type of demodulator,
    • a block Signal adapter that adjusts the levels and corrects the residual intensity modulation of the SOA through the EAM,
    and characterized in that the SOA and EAM photonic elements are modulated directly with the respective phase and module combinations of each symbol in the complex QAM constellation, from the digital information to be transmitted, by:
    to. a direct electrical signal to the SOA consisting of discrete pulsations of several levels at different levels of "0" (reference central value), and which produces an optical signal whose optical phase is modulated in such a way that:
    • the positive current levels, with respect to the polarization current, represent positive time advances or phase variations, while negative current levels represent delay or negative phase variations.
    • the amplitudes of the pulse are adjusted so that its value multiplied by the "chirp" factor of the SOA offers the desired phase in each symbol of the constellation.
    b. an electrical voltage signal to the EAM corresponding to the amplitude or modulus of the QAM symbol to be transmitted, to which a sample of the injection current signal is subtracted from the SOA, to compensate for the residual intensity modulation in the SOA.
    [5]
    The method according to any of the preceding Claims wherein the defined functions of the Differential Precoder, Pulse Encoder or Adapter blocks are performed in the Mapper block with digital processing of the signal.
    类似技术:
    公开号 | 公开日 | 专利标题
    RU2662230C1|2018-07-25|Optical transmitter with pre-compensation of dispersion dependent on optical receiver
    US7978390B2|2011-07-12|Optical modulator
    Cano et al.2014|Direct phase modulation DFBs for cost-effective ONU transmitter in udWDM PONs
    US6473214B1|2002-10-29|Methods of and apparatus for optical signal transmission
    US20060159466A1|2006-07-20|Offset quadrature phase-shift-keying method and optical transmitter using the same
    CN112583492A|2021-03-30|Method and apparatus for detecting and compensating for power imbalance and modulation imperfections for coherent optical transmitters
    JP6482070B2|2019-03-13|Method for generating optical two-tone signal and method for controlling DP-MZM type optical modulator
    US9523867B2|2016-12-20|Off quadrature biasing of Mach Zehnder modulator for improved OSNR performance
    Cano et al.2015|DQPSK directly phase modulated DFB for flexible coherent UDWDM-PONs
    US20150249504A1|2015-09-03|Optical Transmitter
    CN103168437A|2013-06-19|Self-adaptive receivers not requiring fec feedback
    Corsini et al.2015|10-Gb/s long-reach PON system with low-complexity dispersion-managed coherent receiver
    WO2006131904A1|2006-12-14|Dispersion compensation
    ES2695901B2|2019-11-28|OPTICAL TRANSMITTER WITH DUAL PHASE AND AMPLITUDE MODULATION
    US10715255B2|2020-07-14|Off quadrature mach-zehnder modulator biasing
    Velásquez et al.2017|15-dB differential link-loss UDWDM-PON with direct beat phase modulated DFBs
    Li et al.2018|Photonic generation of microwave binary digital modulation signal with format agility and parameter tunability
    JP6701144B2|2020-05-27|Light modulator
    Velásquez et al.2017|Direct Beat Phase Modulated DFB for flexible 1.25-5 Gb/s Coherent UDWDM-PONs
    Paskov2015|Algorithms and subsystems for next generation optical networks
    Sakamoto et al.2009|High-bit-rate optical QAM
    Prat et al.2019|Direct PSK-ASK modulation for coherent udWDM
    Zhang et al.2016|IMDD-based bidirectional 20 Gb/s/λ WDM-PON with Nyquist 4 PAM employing Rayleigh backscattering noise detection-based self wavelength management
    Straullu et al.2017|Symmetric 10 Gbps PON operating with a single laser over 31 dB of ODN Loss
    JP2016218190A|2016-12-22|Optical two-tone signal generating method, and dp-mzm type optical modulator control method
    同族专利:
    公开号 | 公开日
    ES2695901B2|2019-11-28|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2019-01-11| BA2A| Patent application published|Ref document number: 2695901 Country of ref document: ES Kind code of ref document: A1 Effective date: 20190111 |
    2019-11-28| FG2A| Definitive protection|Ref document number: 2695901 Country of ref document: ES Kind code of ref document: B2 Effective date: 20191128 |
    优先权:
    申请号 | 申请日 | 专利标题
    ES201730902A|ES2695901B2|2017-07-06|2017-07-06|OPTICAL TRANSMITTER WITH DUAL PHASE AND AMPLITUDE MODULATION|ES201730902A| ES2695901B2|2017-07-06|2017-07-06|OPTICAL TRANSMITTER WITH DUAL PHASE AND AMPLITUDE MODULATION|
    [返回顶部]