CN117240369B

CN117240369B - Optical signal spectrum synthesis method and system

Info

Publication number: CN117240369B
Application number: CN202311527877.1A
Authority: CN
Inventors: 曹子峥; 皮雅稚
Original assignee: Peng Cheng Laboratory
Current assignee: Peng Cheng Laboratory
Priority date: 2023-11-16
Filing date: 2023-11-16
Publication date: 2024-02-13
Anticipated expiration: 2043-11-16
Also published as: CN117240369A

Abstract

The invention belongs to the technical field of high-speed optical communication, and discloses an optical signal spectrum synthesis method and an optical signal spectrum synthesis system. According to the invention, a plurality of paths of modulation signals are modulated onto a plurality of paths of optical local oscillation signals through a transmitting end, so that a plurality of paths of signals to be synthesized are obtained, the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship; the method comprises the steps that a sending end synthesizes a plurality of paths of signals to be synthesized to obtain synthesized signals, and the synthesized signals are transmitted to a receiving end through optical fibers; the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, so that channel expansion of a high-speed system is avoided, and the high-speed DAC and the high-speed ADC are excessively relied on, so that the channel capacity is prevented from being limited by bandwidth, and synthesis and detection from low baud rate to high baud rate are simply and flexibly realized.

Description

Optical signal spectrum synthesis method and system

Technical Field

The present invention relates to the field of high-speed optical communications technologies, and in particular, to a method and a system for synthesizing an optical signal spectrum.

Background

The digital-to-analog converter (DAC, digital to Analog Converter) and the analog-to-digital converter (ADC, analog to Digital Converter) in the optical signal modulation system have limited bandwidths, and the analog bandwidths of the digital-to-analog converter and the analog-to-digital converter are not greatly expanded in a short period; the basic component used to implement a high symbol rate QAM transmitter is a high-speed DAC, and bandwidth limitations of the DAC become a major factor in limiting the symbol rate achievable in a high symbol rate system. Furthermore, even if the modulation order is increased at the cost of the transmission distance, the high-speed DAC and the high-speed ADC are indispensable for transceiving the high-modulation order signal, and therefore, the bandwidth limitation of the DAC/ADC also limits the channel capacity in the high-modulation order system. Bandwidth extension techniques using parallel DAC/ADC architecture and additional analog electronics, but add complexity and cost to the transceiver.

The foregoing is provided merely for the purpose of facilitating understanding of the technical solutions of the present invention and is not intended to represent an admission that the foregoing is prior art.

Disclosure of Invention

The invention mainly aims to provide an optical signal spectrum synthesis method and system, and aims to solve the technical problem that the prior art depends on bandwidth limitation of electronic devices and cannot better improve channel capacity.

In order to achieve the above object, the present invention provides an optical signal spectrum synthesis method, which is applied to an optical signal spectrum synthesis system, wherein the optical signal spectrum synthesis system includes a transmitting end and a receiving end, and the transmitting end and the receiving end are connected through an optical fiber;

the transmitting end modulates a plurality of paths of modulation signals onto a plurality of paths of optical local oscillation signals to obtain a plurality of paths of signals to be synthesized, wherein the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship;

the sending end synthesizes the signals to be synthesized to obtain a synthesized signal, and transmits the synthesized signal to the receiving end through an optical fiber;

And the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy.

Optionally, the plurality of optical local oscillation signals are a plurality of optical signals with different wavelengths of the transmitting end, and before the transmitting end modulates the plurality of modulation signals onto the plurality of optical local oscillation signals to obtain a plurality of signals to be synthesized, the method further includes:

the sending end obtains the signals to be synthesized through a preset algorithm;

and modulating the in-phase component and the quadrature component of the plurality of paths of modulation signals onto the plurality of paths of optical local oscillation signals respectively by configuring the modulation symbol rate on each optical carrier, the carrier interval frequency and the phase relation, and modulating to obtain the plurality of signals to be synthesized.

Optionally, the transmitting end synthesizes the signals to be synthesized to obtain a synthesized signal, which includes:

and directly coupling the power of the signals to be synthesized to obtain the synthesized signal.

Optionally, the receiving end includes a digital signal processing module, and the receiving end recovers the modulation signal from the composite signal according to a preset demodulation policy, including:

when the modulation signal of the transmitting end is not precoded, the digital signal processing module sequentially carries out dispersion compensation, time domain blind equalization, frequency offset estimation and phase recovery processing on the synthesized signal to obtain a first signal;

The digital signal processing module performs Fourier transform on the first signal to obtain a second signal;

and the digital signal processing module detects the second signal to obtain the modulation signal.

Optionally, the receiving end recovers the modulation signal from the composite signal according to a preset demodulation policy, and further includes:

when the modulation signal of the transmitting end is pre-coded, the digital signal processing module sequentially carries out dispersion supplementation, time domain blind equalization, frequency offset estimation and phase recovery processing on the synthesized signal to obtain a first signal;

and the digital signal processing module carries out maximum likelihood sequence detection on the first signal to obtain the modulation signal.

Optionally, the receiving end includes a digital signal processing module, a photodetector array, a low-pass filter array, an analog-to-digital converter array, and an optical mixer array, and the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, including:

when the preset demodulation strategy is an asymmetric receiving strategy, the receiving end generates a receiving end optical local oscillator signal;

the receiving end inputs the receiving end optical local oscillation signal and the synthesized signal into the optical mixer array to obtain an in-phase component and a quadrature component of the synthesized signal; the center frequencies of the optical local oscillation signals and the synthesized signals are equal;

The receiving end converts the in-phase component and the quadrature component into an electric signal through the photoelectric detector; and obtaining fundamental frequency analog data of the synthesized signal through the low-pass filter array, performing analog-to-digital conversion through the analog-to-digital converter array to obtain a digital signal, and inputting the digital signal to the digital signal processing module for recovery to obtain the modulation signal.

Optionally, the receiving end includes a digital signal processing module, an optical mixer array, a photodetector array, a low-pass filter array, and an analog-to-digital converter array, and the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

when the preset demodulation strategy is a symmetrical receiving strategy, the receiving end divides the synthesized signal into N paths and generates N paths of receiving end optical local oscillation signals with the same frequency as the local oscillation signals generated by the transmitting end;

inputting the N paths of optical local oscillation signals of the receiving end and the synthesized signals into an optical mixer array respectively to obtain an in-phase component shunt and a quadrature component shunt of a frequency spectrum which takes the optical local oscillation signals of the receiving end as a central frequency and is preset to be multiplied by an optical carrier frequency interval;

The receiving end inputs the in-phase component taking the receiving end optical local oscillation signal as the center frequency to the photoelectric detector array, the low-pass filter array and the analog-to-digital converter array to obtain the in-phase component of the frequency spectrum;

the receiving end inputs the orthogonal component taking the optical local oscillation signal of the receiving end as the center frequency to the photoelectric detector array, the low-pass filter array and the analog-to-digital converter array to obtain the orthogonal component of the frequency spectrum;

and inputting the in-phase component and the quadrature component to the digital signal processing module for recovery to obtain the modulation signal.

Optionally, the receiving end includes a digital signal processing module, an optical mixer array, a photodetector array, a band-pass filter array, an electrical mixer array, a low-pass filter array, and an analog-to-digital converter array, and the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

when the preset demodulation strategy is a symmetrical receiving strategy, the receiving end inputs the synthesized signal and a receiving end optical local oscillator signal to the optical mixer array to respectively obtain an in-phase component synthesized signal and a quadrature component synthesized signal; the center frequencies of the optical local oscillation signals and the synthesized signals are equal;

The receiving end inputs the in-phase component synthesized signal to the photoelectric detector array, converts the optical signal into an electric signal, and then divides the electric signal into N paths to obtain N paths of in-phase component shunt electric signals;

the receiving end inputs all paths of in-phase component shunt signals to the band-pass filter array respectively to be filtered according to a preset filtering strategy, and a filtering wave band is obtained;

the receiving end generates electric local oscillator signals, the center frequency of each path of the electric local oscillator signals is the same as the center frequency of each path of the band-pass filter array, the filtering wave band and the electric local oscillator signals are input to the electric mixer array to be subjected to frequency mixing down-conversion treatment, the frequency mixing result is input to the low-pass filter array to obtain low-frequency signals of each path of in-phase components, and the frequency of the electric local oscillator signals is as follows: k represents BW/N, wherein k represents 0 to (N-1), BW=N represents Δf, and Δf represents the carrier frequency interval of the transmitting end;

the receiving end inputs the orthogonal component synthesized signals to the photoelectric detector array, and divides the detected electric signals into N paths to obtain N paths of orthogonal component shunt electric signals;

the receiving end inputs the orthogonal component shunt signals of each path to the band-pass filter array respectively, and filters the signals according to a preset filtering strategy to obtain filtered wave bands;

The receiving end acquires the electric local oscillator signal, inputs the filtered wave band and the electric local oscillator signal into the mixer to carry out frequency mixing down-conversion treatment, and inputs a frequency mixing result into the low-pass filter array to obtain low-frequency signals of all the orthogonal components;

and the receiving end carries out analog-to-digital conversion on the in-phase component low-frequency signal and the quadrature component low-frequency signal, and then inputs the signals to the digital signal processing module for recovery to obtain the modulation signal.

Optionally, the receiving end includes a digital signal processing module, an optical mixer array, a photodetector array, a time division demultiplexer, and an analog-to-digital converter array, and the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

when the preset demodulation strategy is an asymmetric receiving strategy, the receiving end inputs the synthesized signal and a receiving end optical local oscillator signal into the optical mixer array to respectively obtain an in-phase component synthesized signal and a quadrature component synthesized signal, wherein the center frequencies of the optical local oscillator signal and the synthesized signal are equal;

the receiving end inputs the in-phase component synthesized signal to the photoelectric detector array and the time division demultiplexer for time division demultiplexing, the in-phase component synthesized signal is demultiplexed into multipath in-phase component split signals, and the frequency spectrum widths of the in-phase component split signals are all the optical carrier frequency intervals;

The receiving end inputs the multipath in-phase component shunt signals to the analog-to-digital converter array to obtain multipath in-phase components;

the receiving end inputs the quadrature component synthesized signals to the photoelectric detector array and the time division demultiplexer for time division demultiplexing, the quadrature component synthesized signals are demultiplexed into multipath in-phase component branch signals, and the frequency spectrum widths of the in-phase component branch signals are all the optical carrier frequency intervals;

the receiving end inputs the multipath orthogonal component branching signals to the analog-to-digital converter array to obtain multipath orthogonal components;

the receiving end inputs the multipath in-phase components and the multipath quadrature components to the digital signal processing module for recovery, and the modulation signal is obtained.

In addition, in order to achieve the above objective, the present invention further provides an optical signal spectrum synthesis system, where the optical signal spectrum synthesis system includes a transmitting end and a receiving end, the transmitting end and a receiving end host are connected through an optical fiber, and the optical signal spectrum synthesis system is used in the optical signal spectrum synthesis method.

According to the invention, a plurality of paths of modulation signals are modulated onto a plurality of paths of optical local oscillation signals through a transmitting end, so that a plurality of paths of signals to be synthesized are obtained, the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship; the sending end synthesizes a plurality of paths of signals to be synthesized to obtain synthesized signals, and the synthesized signals are transmitted to the receiving end through optical fibers; the receiving end detects the synthesized signal to obtain a detection result of the synthesized signal, matches a demodulation strategy according to the detection result, recovers a modulation signal from the synthesized signal according to the demodulation strategy, and avoids the high-speed DAC and the high-speed ADC from excessively depending on the high-modulation-order signal, thereby avoiding the limitation of the bandwidth on the channel capacity and simply and flexibly realizing the synthesis and detection from the low baud rate to the high baud rate.

Drawings

FIG. 1 is a system processing flow chart of the optical signal spectrum synthesis method of the present invention;

FIG. 2 is a block diagram illustrating a system architecture of an embodiment of a method for synthesizing optical signal spectrum according to the present invention;

FIG. 3 is a system processing flow chart including a specific processing flow of a receiving end DSP in the optical signal spectrum synthesis method of the invention;

FIG. 4 is a schematic diagram of a detection scheme of a receiving-end DSP without precoding at a transmitting end according to an embodiment of the optical signal spectrum synthesis method of the present invention;

FIG. 5 is a schematic diagram of a detection scheme of a receiving-end DSP when precoding is performed at a transmitting end according to an embodiment of the optical signal spectrum synthesis method of the present invention;

FIG. 6 is a schematic diagram illustrating asymmetric receiving at a transceiver according to an embodiment of the spectrum synthesis method of the present invention;

FIG. 7 is a schematic diagram illustrating symmetric receiving at a transceiver according to an embodiment of the spectrum synthesis method of the present invention;

FIG. 8 is another receiving schematic diagram of transceiver symmetry according to an embodiment of the spectrum synthesis method of the present invention;

FIG. 9 is a schematic diagram illustrating another receiving scheme of transceiver symmetry according to an embodiment of the spectrum synthesis method of the optical signal of the present invention;

fig. 10 is a schematic diagram illustrating connection between a transmitting end and a receiving end in an embodiment of an optical signal spectrum synthesis method according to the present invention.

The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

An embodiment of the present invention provides a method for synthesizing optical signal spectrum, referring to fig. 1, fig. 1 is a schematic flow chart of a first embodiment of optical signal spectrum synthesis according to the present invention.

In this embodiment, the optical signal spectrum synthesis method includes the following steps:

step S10: the transmitting end modulates a plurality of paths of modulation signals onto a plurality of paths of optical local oscillation signals to obtain a plurality of paths of signals to be synthesized, the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship.

It should be noted that the present embodiment is applied to an optical signal spectrum synthesis system, where the optical signal spectrum synthesis system includes a transmitting end and a receiving end, and the transmitting end and the receiving end are connected by an optical fiber.

It should be understood that, in order to solve the problem that the channel capacity is limited by the bandwidth limitation of the DAC/ADC of the electronic device in the high-speed optical communication system, the present embodiment provides a direct spectrum synthesis method, in which different signals are modulated on multiple optical carriers respectively, each path of modulated signal can reach the highest baud rate limited by the bandwidth of the DAC, then direct spectrum synthesis is performed, the final bandwidth in the system is several times of the limited bandwidth of the DAC, the baud rate transmitted in the system is increased by equal times, and the low baud rate is synthesized to high baud rate, thereby realizing the channel capacity in the expansion system. When modulating different signals on multiple optical carriers, the baseband IQ signal can be expressed as follows:

（1）

Wherein S is the last synthesized signal in the time domain, C is the modulated signal on each optical carrier, N is the number of carriers, and N represents the carrier number of the current signal.

Based on the above equation (1), the relation between the time domain signal S and the frequency domain signal C can be obtained using a discrete time representation:

（2）

the frequency and the period are related as follows:

（3）

the above expression (2) can be written in matrix form:

=/>（4）

in practice this matrix T is a digital fourier transform, and the above expression (4) can be further written as:

（5）

where F is the Fourier transform matrix.

At this time, one symbol in one period can be clearly known, and the spectrum combination can be realized to reach the N times of baud rate through N paths of combination.

It should be noted that, the signal to be synthesized refers to a signal modulated by a single path of modulation signal and an optical local oscillation signal generated by a local oscillator.

In a specific implementation, referring to fig. 2, fig. 2 is a system structural block diagram of the present embodiment. The transmitting end comprises N paths of modulation signals, a local oscillator of the transmitting end can correspondingly generate N optical local oscillation signals TLO, each path of modulation signals can be divided into an in-phase component I and a quadrature component Q, and the transmitting end comprises I of a first path of modulation signals ₁ The component 102, after passing through the low-pass filter 103, is carrier-suppressed modulated by the modulator 104, and modulated onto the first optical carrier TLO-1 101. At the same time, Q of the first path of modulation signal ₁ The component 105 is modulated by the modulator 108 onto the optical carrier wave of which the first path of optical carrier wave 101 is subjected to 90 ° phase shift by the phase shifter 105 after passing through the low-pass filter 107. The multipath signals of the transmitting end are modulated in the same mode in turn, and the I of the N-th modulated signal _n The component 110 is passed through a low-pass filter 111, and then subjected to carrier-reject modulation by a modulator 112, and modulated onto an nth optical carrier TLO-N109. At the same time, Q of the Nth modulated signal _n The component 113 is modulated by a modulator 116 onto an optical carrier wave 90 ° phase-shifted by a phase shifter 114 from the nth optical carrier wave 109 after passing through a low-pass filter 115. Modulating the I component and the Q component of the modulated signal to the corresponding optical carrier wave of each path to obtain the signal to be synthesized.

Further, the plurality of optical local oscillation signals are a plurality of optical signals with different wavelengths of the transmitting end, the transmitting end modulates the plurality of modulation signals onto the plurality of optical local oscillation signals to obtain a plurality of signals to be synthesized, and before the signals to be synthesized are obtained, the method further comprises the steps of:

In a specific implementation, before a transmitting end modulates a plurality of paths of modulation signals onto a plurality of paths of optical local oscillation signals to obtain a plurality of paths of signals to be synthesized, a plurality of paths of signals to be synthesized can be obtained through a preset algorithm by reverse thrust, and in-phase components and quadrature components of the plurality of paths of modulation signals are respectively modulated onto the plurality of paths of optical local oscillation signals by configuring modulation symbol rates and carrier interval frequency and phase relations on all optical carriers, so that the plurality of signals to be synthesized are obtained.

Step S20: the sending end synthesizes the signals to be synthesized to obtain a synthesized signal, and transmits the synthesized signal to the receiving end through an optical fiber.

In a specific implementation, each signal is modulated and then combined in the optical coupler 117. As is clear from expression (5), the spectrum synthesis achieved based on this approach is equivalent to fourier transform. Depending on the signal S (k) to be modulated, it is also possible by a simple mapping relation, for example: look-Up Table, LUT, look-Up-Table and the like for precoding modulated signals The precoding is equivalent to inverse fourier transform. Therefore, in this embodiment, the processing manner of the modulated signal can be practically divided into two types: one is that the transmitting end does not do any processing and precoding to the modulated signal; one is to first precode the modulated signal at the transmitting end. If the sender does not do anything, the modulated I component 110I of FIG. 1 _n Then for modulated signal C _n Directly taking in-phase component, modulated Q component 113Q _n Then for modulated signal C _n The quadrature component is taken directly. If the modulated signal is precoded at the transmitting end, the modulated signal C is first _n Performing inverse Fourier transform precoding to obtain ∈>Then toTaking the in-phase component to obtain a modulated I component 110I _n The method comprises the steps of carrying out a first treatment on the surface of the For->Taking the quadrature component to obtain a modulated Q component 113Q _n . After the composite signal is obtained, the composite signal is then transmitted to the receiving end via the optical fiber 118.

Further, when the transmission end synthesizes the signals to be synthesized to obtain a synthesized signal, the synthesized signal can be obtained through direct power coupling.

Step S30: and the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy.

It should be noted that, the preset demodulation strategy is a demodulation method of the synthesized signal, and different synthesized signal features correspond to different demodulation modes.

In a particular implementation, the composite signal is transmitted to the receiving end via optical fiber 118. The receiving end performs coherent optical receiving demodulation on the synthesized signal and the received optical local oscillation signal 120, demodulates I, Q components of the signal respectively, inputs the I/Q component signals to the DSP module 121 at the same time, and completes one-line operations such as dispersion compensation, frequency offset estimation, channel estimation, equalization, phase compensation and the like in the DSP module, thereby recovering the modulated signal.

In the embodiment, a plurality of paths of modulation signals are modulated onto a plurality of paths of optical local oscillation signals through a transmitting end to obtain a plurality of paths of signals to be synthesized, the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship; the sending end synthesizes a plurality of paths of signals to be synthesized to obtain synthesized signals, and the synthesized signals are transmitted to the receiving end through optical fibers; the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, so that channel expansion of a high-speed system is avoided, and the high-speed DAC and the high-speed ADC are excessively relied on, so that the channel capacity is prevented from being limited by bandwidth, and synthesis and detection from low baud rate to high baud rate are simply and flexibly realized.

Referring to fig. 3, fig. 3 is a system processing flow chart of an optical signal spectrum synthesis method according to the present invention, which includes a specific processing flow of a receiving end DSP.

Based on the above first embodiment, the optical signal spectrum synthesis method of this embodiment includes, in the step S30:

step S301: when the modulation signal of the transmitting end is not precoded, the digital signal processing module sequentially carries out dispersion compensation, time domain blind equalization, frequency offset estimation and phase recovery processing on the synthesized signal to obtain a first signal.

Step S302: the digital signal processing module performs Fourier transform on the first signal to obtain a second signal.

Step S303: and the digital signal processing module detects the second signal to obtain the modulation signal.

It should be noted that, the receiving end includes a digital signal processing module, the first signal refers to a signal obtained by combining, and the second signal refers to a recovered signal processed by the digital signal processing module.

In a specific implementation, whether the signal sent by the sending end performs precoding affects what mode the receiving end should perform signal demodulation. When the precoding is not performed, the signals of adjacent channels are overlapped with each other, so that the number of the modulation signal levels is increased, and the M2-QAM is changed into the K2-QAM, wherein K > M. Blind estimation/equalization is performed at the receiving end, and the combined signal K2-QAM can be recovered to the required modulation signal M2-QAM. Referring to fig. 4, fig. 4 is a schematic diagram of a detection scheme of a DSP at a receiving end, where the DSP is not precoded at a transmitting end. In the digital signal processing module, the signals are sequentially subjected to dispersion compensation 201, a cascade multimode algorithm 202 is subjected to time domain blind equalization, frequency offset estimation 203 is performed, phase recovery 204 is performed to obtain K2-QAM signals 205, inverse Fourier transform 206 is performed to recover M2-QAM signals 207, and finally the recovered M2-QAM signals are detected 208, so that modulation signals can be recovered.

Further, the receiving end includes a digital signal processing module, and the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

In a specific implementation, referring to fig. 5, fig. 5 is a schematic diagram of a detection scheme of a DSP at a receiving end for precoding at a transmitting end. If the modulated signal is precoded at the transmitting end in the digital signal processing module, the signal is sequentially subjected to dispersion supplementation 301, a cascade multimode algorithm 302 performs time domain blind equalization, frequency offset estimation 303 and phase recovery 304, a K2-QAM signal 305 is obtained, and then maximum likelihood sequence detection 306 is directly performed, so that the modulated signal can be recovered.

Further, the receiving end includes a digital signal processing module, a photo detector array, a low-pass filter array, an analog-to-digital converter array and an optical mixer array, and recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, including:

the receiving end converts the in-phase component and the quadrature component into an electric signal through the photoelectric detector array; and obtaining fundamental frequency analog data of the synthesized signal through the low-pass filter array, performing analog-to-digital conversion through the analog-to-digital converter array to obtain a digital signal, and inputting the digital signal to the digital signal processing module for recovery to obtain the modulation signal.

In a specific implementation, referring to fig. 6, fig. 6 is a schematic diagram of asymmetric receiving at a transceiver. The signal is transmitted through the optical fiber to the receiving end, where an optical local oscillation signal 401 is used, and the frequency of the optical local oscillation signal should be the center frequency of the spread spectrum. The optical local oscillation signal 401 and the optical fiber transmission signal are input into the optical mixer 401 and the optical mixer 406, respectively, the I, Q component of the synthesized signal is subjected to coherent reception down-conversion, wherein the I component is subjected to photoelectric detection through the photodiode 403, the optical signal is converted into an electric signal, then the fundamental frequency component after frequency synthesis is filtered out through the low-pass filter 404, and the fundamental frequency component at the moment refers to the fundamental frequency with high speed after synthesis, so that the analog-to-digital conversion is performed by a corresponding high-bandwidth analog-to-digital converter 405; similarly, the Q component is photo-detected by photodiode 407, then passed through low pass filter 408, and then analog-to-digital converted by a high bandwidth analog-to-digital converter 409 (ADC). And then the I, Q component is input to the DSP digital signal processing module 410 at the same time, so that the receiving end demodulates according to whether the modulation signal of the transmitting end is precoded or not, and a demodulation signal is obtained.

Further, the receiving end includes a digital signal processing module, an optical mixer array, a photoelectric detector array, a low-pass filter array, and an analog-to-digital converter array, and recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

inputting the N paths of optical local oscillator signals of the receiving end and the synthesized signals into an optical mixer array respectively to obtain N paths of in-phase component branches and quadrature component branches of a frequency spectrum which takes the optical local oscillator signals of the receiving end as a center frequency and is preset to be multiplied by an optical carrier frequency interval;

In a specific implementation, referring to fig. 7, fig. 7 is a schematic diagram of receiving symmetric to a transceiver. The signal is transmitted by the optical fiber to reach the receiving end, and the corresponding receiving end adopts N paths of optical coherent receiving down-conversion. The frequency of the optical local oscillator signal 501 at the receiving end corresponds to the frequency of the TLO-1 at the transmitting end, and the frequencies are equal. The received synthesized signal and the optical local oscillator signal 501 are subjected to coherent reception down-conversion in the optical mixer 502, so as to obtain a frequency spectrum which takes the optical local oscillator signal 501 as a center frequency and is 2 times of the optical carrier frequency interval, and the frequency spectrum is shown in fig. 7 and divided into I, Q components. An I component signal with the optical local oscillation signal 501 as a center frequency passes through a photodetector 503, a low-pass filter 504 and an analog-to-digital converter 505 to obtain an I component of the frequency spectrum; the Q component signal with the optical local oscillation signal 501 as the center frequency passes through the photodetector 506, the low-pass filter 507, and the analog-to-digital converter 508 to obtain the Q component of the spectrum. Similarly, the frequency of the optical local oscillator signal 509 at the receiving end corresponds to the frequency of the TLO-2 at the transmitting end, and the frequencies are equal. The received synthesized signal and the optical local oscillation signal 509 are subjected to coherent reception down-conversion in the optical mixer 510, so as to obtain a frequency spectrum which takes the optical local oscillation signal 509 as a center frequency and is 2 times of the optical carrier frequency interval, and the frequency spectrum is divided into I, Q components. An I component signal with the optical local oscillation signal 509 as a center frequency passes through the photodetector 511, the low-pass filter 512, and the analog-to-digital converter 513 to obtain an I component of the spectrum; the Q component signal having the optical local oscillation signal 509 as the center frequency is passed through a photodetector 514, a low-pass filter 515, and an analog-to-digital converter 516 to obtain the Q component of the spectrum. Similarly, the frequency of the optical local oscillator signal 517 at the receiving end corresponds to the frequency of the TLO-N at the transmitting end, and the frequencies are equal. The received synthesized signal and the optical local oscillation signal 517 are subjected to coherent reception down-conversion in the optical mixer 518, so as to obtain a frequency spectrum which takes the optical local oscillation signal 517 as a center frequency and is 2 times of the optical carrier frequency interval, and the frequency spectrum is divided into I, Q components. An I component signal with the optical local oscillation signal 517 as a center frequency passes through the photodetector 519, the low pass filter 520, and the analog-to-digital converter 521 to obtain an I component of the spectrum; the Q component signal having the optical local oscillation signal 517 as the center frequency passes through the photodetector 522, the low-pass filter 523, and the analog-to-digital converter 524, and thus the Q component of the spectrum is obtained. Finally, each path of I/Q component is input to the DSP digital signal processing module 525 at the same time, so that the receiving end demodulates according to whether the modulating signal of the sending end is precoded or not, and a demodulation signal is obtained.

Further, the receiving end includes a digital signal processing module, an optical mixer array, a photoelectric detector array, a band-pass filter array, an electrical mixer array, a low-pass filter array and an analog-to-digital converter array, and recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

when the preset demodulation strategy is a symmetrical receiving strategy, the receiving end inputs the synthesized signal and a receiving end optical local oscillator signal to the optical mixer array to respectively obtain an in-phase component synthesized signal and a quadrature component synthesized signal;

the receiving end inputs the paths of in-phase component shunt signals to the band-pass filter array respectively to be filtered according to a preset filtering strategy, and a filtering wave band is obtained;

the receiving end obtains electric local oscillator signals, the center frequency of each path of electric local oscillator signals is the same as the center frequency of each path of band pass filters, the filtering wave band and the electric local oscillator signals are input to the electric mixer array to be subjected to frequency mixing down-conversion processing, the frequency mixing result is input to the low-pass filter array, and low-frequency signals of each path of in-phase components are obtained, and the frequencies of the electric local oscillator signals are as follows: k represents BW/N, wherein k represents 0 to (N-1), BW=N represents Δf, and Δf represents the carrier frequency interval of the transmitting end;

The receiving end inputs the orthogonal component synthesized signals to the photoelectric detector array, converts optical signals into electric signals, divides the electric signals into N paths, and divides the electric signals into N paths to obtain N paths of orthogonal component shunt electric signals;

In a specific implementation, referring to fig. 8, fig. 8 is another receiving schematic diagram of transceiver symmetry. The signal is transmitted through the optical fiber to reach the receiving end, and enters the optical mixer 602 together with the optical local oscillator signal 601 to obtain I, Q component synthesized signals respectively, wherein the frequency of the optical local oscillator signal is the center frequency of the synthesized frequency spectrum. The I component synthesized signal is divided into N paths after passing through the photodetector 603, each path enters a low-pass or band-pass filter respectively, wherein the first path enters the low-pass filter, the other paths enter the band-pass filter respectively, each path filters out a frequency band with an initial frequency (N-1) Δf and a frequency spectrum width Δf respectively, and Δf is a carrier frequency interval of a transmitting end. The filtered wave band is mixed with the electric local oscillation signal by a mixer, the frequency spectrum is moved to a low frequency wave band and a high frequency wave band, then the high frequency signal is filtered by a low-pass filter, the low frequency signal of the wave band is obtained, and the frequency of the electric local oscillation signal is as follows: k represents BW/N, wherein k represents 0 to (N-1), and BW=N represents Δf. The first path of signal is filtered out with wave band of 0 to delta f after passing through the low pass filter 604, and then mixed with the electric local oscillation signal 606 in the mixer 605, and ELO-1 at the moment is 0 frequency, so that the sum and difference obtained after the first path of signal and the 0 frequency pass through the mixer are still the signal itself, and then the signal is input into the DSP module 625 through the low pass filter 607 and the analog-digital converter 608; the N-th signal is filtered out by a band-pass filter 609, the wave band is (N-1) Deltaf-N Deltaf, then mixed with an electric local oscillation signal 611 in a mixer 610, the ELO-N frequency is (N-1) Deltaf, after the two signals pass through the mixer, the wave band filtered out by the band-pass filter is shifted to two positions of 0 Deltaf and (2N-1) Deltaf-2N Deltaf by frequency spectrums, and then the wave band is input to a DSP module 625 by a low-pass filter 612 and an analog-digital converter 613. The Q component is also processed in the same way, and the Q component synthesized signal is split into N paths after passing through the photodetector 614, where each path enters a low-pass or band-pass filter, respectively, and the first path enters the low-pass filter, and the other paths enter the band-pass filter, respectively. The first path of signal is filtered out with wave band of 0 to delta f after passing through the low pass filter 615, then mixed with the electric local oscillation signal 617 in the mixer 616, and ELO-1 at the moment is 0 frequency, so that the sum and difference obtained after passing through the mixer between the first path of signal and the 0 frequency is still the signal itself, and then the signal is input into the DSP module 625 through the low pass filter 618 and the analog-to-digital converter 619; the nth signal is filtered out by a band-pass filter 620, the band is (N-1) Δf-N Δf, then mixed with an electric local oscillator signal 622 in a mixer 621, the ELO-N frequency is (N-1) Δf, after both signals pass through the mixer, the band filtered out by the band-pass filter is shifted to two positions of 0 to Δf and (2N-1) Δf-2N Δf by frequency spectrums, and then input to a DSP module 625 by a low-pass filter 623 and an analog-digital converter 624. All the I/Q component signals are finally input to the digital signal processing module 625 at the same time, so that the receiving end demodulates according to whether the modulation signal of the transmitting end is precoded, and a demodulated signal is obtained.

Further, the receiving end includes a digital signal processing module, an optical mixer array, a photoelectric detector array, a time division demultiplexer, and an analog-to-digital converter array, and recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, and further includes:

when the preset demodulation strategy is a symmetrical receiving strategy, the receiving end inputs the synthesized signal and a receiving end optical local oscillator signal to the optical mixer array to respectively obtain an in-phase component synthesized signal and a quadrature component synthesized signal, wherein the center frequencies of the optical local oscillator signal and the synthesized signal are equal;

the receiving end inputs the in-phase component synthesized signal to the photoelectric detector array and the time division demultiplexer for time division demultiplexing, the in-phase component synthesized signal is demultiplexed into multipath in-phase component branching signals, and the frequency spectrum widths of the in-phase component branching signals are all the optical carrier frequency intervals;

the receiving end inputs the multipath in-phase component shunt signals to the analog-to-digital converter array to obtain multipath in-phase component signals;

the receiving end inputs the orthogonal component synthesized signal to the photoelectric detector and the time division demultiplexer for time division demultiplexing, the orthogonal component synthesized signal is demultiplexed into a plurality of orthogonal component branch signals, and the frequency spectrum widths of the orthogonal component branch signals are all the optical carrier frequency intervals;

The receiving end inputs the multipath orthogonal component shunt signals to the analog-to-digital converter array to obtain multipath orthogonal component signals;

In a specific implementation, referring to fig. 9, fig. 9 is another receiving schematic diagram of transceiver symmetry. The signal is transmitted through the optical fiber to reach the receiving end, and enters the optical mixer 702 together with the optical local oscillator signal 701 to obtain I, Q component synthesized signals respectively, wherein the frequency of the optical local oscillator signal is the center frequency of the synthesized frequency spectrum. The I component signal enters a time division demultiplexer 705 after passing through a photoelectric detector 703, the synthesized signal is demultiplexed into multiple paths for down conversion after time division demultiplexing, the frequency spectrum width of each path of signal is the frequency interval of an optical carrier, and then each path of signal is subjected to analog-to-digital conversion 706, 707 and 708 respectively; the I component signal passes through the photodetector 704, enters the time division demultiplexer 709, is demultiplexed into multiple paths through time division demultiplexing, is down-converted, each path of signal has a spectral width equal to an optical carrier frequency interval, and is subjected to analog-to-digital conversion 710, 711 and 712 respectively. And finally, inputting the multiple I components and multiple Q components obtained after transformation into a digital signal processing module 713 at the same time, so that the receiving end demodulates according to whether the modulation signal of the transmitting end is precoded or not, and a demodulation signal is obtained.

According to the embodiment, different signals are modulated on a plurality of optical carriers, and the direct synthesis of the frequency spectrum is realized by skillfully configuring the modulation symbol rate and the carrier interval frequency and phase relation on each optical carrier, so that the frequency spectrum which is several times of the bandwidth limited by a DAC/ADC is achieved, the digital domain partition filtering of the traditional optical domain synthesis is avoided, the optical domain frequency spectrum synthesis can be realized at a lower digital signal processing cost, and the recovery of the modulated signals is completed under the condition that the digital signal processing complexity of a receiving end is not obviously increased.

In addition, the embodiment of the invention also provides an optical signal spectrum synthesis system, which comprises a sending end and a receiving end, wherein the sending end and the receiving end are connected through an optical fiber;

the sending end is used for modulating a plurality of paths of modulation signals onto a plurality of paths of optical local oscillation signals to obtain a plurality of paths of signals to be synthesized, the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship;

the sending end is further used for synthesizing the signals to be synthesized to obtain synthesized signals, and transmitting the synthesized signals to the receiving end through an optical fiber;

The receiving end is used for detecting the synthesized signal to obtain a detection result of the synthesized signal, matching a demodulation strategy according to the detection result, and recovering the modulation signal from the synthesized signal according to the demodulation strategy.

In a specific implementation, referring to fig. 10, fig. 10 is a schematic diagram of connection between a transmitting end and a receiving end. Each path of modulation signal can be divided into an in-phase component I component and a quadrature component Q component, and at a transmitting end, I of a first path of modulation signal ₁ And the component is subjected to carrier suppression modulation on a modulator after passing through a low-pass filter and is modulated onto a first path of optical carrier. At the same time, Q of the first path of modulation signal ₁ The component is modulated to a first path by a modulator after passing through a low-pass filterThe optical carrier is subjected to 90-degree phase shift by the phase shifter. The multipath signals of the transmitting end are modulated in the same mode in turn, and the I of the N-th modulated signal _n The component is modulated onto the nth optical carrier by carrier suppression modulation on a modulator after passing through a low-pass filter. At the same time, Q of the Nth modulated signal _n The component is modulated on a modulator to an optical carrier wave of which the N path of optical carrier wave is subjected to 90-degree phase shift through a phase shifter after passing through a low-pass filter. Each path of signal is modulated respectively, combined on the optical coupler and then transmitted to the receiving end through the optical fiber. At the receiving end, the synthesized signal and the received optical local oscillation signal enter the receiving end together to carry out coherent optical receiving demodulation, I, Q components of the signal are respectively demodulated, the I/Q component signals are simultaneously input into a DSP module, and one-line operations such as dispersion compensation, frequency offset estimation, channel estimation, equalization, phase compensation and the like are completed in the DSP module, so that the modulated signal is recovered.

Further, the receiving end includes a digital signal processing module, the receiving end detects the synthesized signal to obtain a detection result of the synthesized signal, matches a demodulation strategy according to the detection result, and recovers the modulation signal from the synthesized signal according to the demodulation strategy, including:

when the detection result is that no pre-coding exists, the digital signal processing module is used for sequentially carrying out dispersion compensation, time domain blind equalization, frequency offset estimation and phase recovery processing on the synthesized signal to obtain a first signal;

the digital signal processing module is used for carrying out Fourier transform on the first signal to obtain a second signal;

the digital signal processing module is used for detecting the second signal to obtain the modulation signal.

In a specific implementation, when the receiving end demodulates the signal, the signal sent by the sending end needs to be detected, and whether the sending end performs precoding when modulating the signal or not is judged, but whether the sending end performs precoding or not affects what mode the receiving end should use to demodulate the signal. When the receiving end detects that the precoding is not performed, the signals of the adjacent channels are overlapped with each other, so that the number of the modulation signal levels is increased, and M2-QAM is changed into K2-QAM, wherein K > M. Blind estimation/equalization is performed at the receiving end, and the combined signal K2-QAM can be recovered to the required modulation signal M2-QAM. In a digital signal processing module, the signals are subjected to dispersion compensation in sequence, a cascade multimode algorithm is subjected to time domain blind equalization, frequency offset estimation and phase recovery, K2-QAM signals are obtained, inverse Fourier transformation is performed, M2-QAM signals are recovered, and finally the recovered M2-QAM signals are detected, so that the modulated signals can be recovered.

Further, the receiving end includes a digital signal processing module, the receiving end detects the synthesized signal to obtain a detection result of the synthesized signal, matches a demodulation strategy according to the detection result, recovers the modulation signal from the synthesized signal according to the demodulation strategy, and further includes:

when the detection result is precoding, the digital signal processing module is used for sequentially carrying out dispersion supplementation, time domain blind equalization, frequency offset estimation and phase recovery processing on the synthesized signal to obtain a first signal;

and the digital signal processing module is used for carrying out maximum likelihood sequence detection on the first signal to obtain the modulation signal.

In a specific implementation, if the modulated signal is precoded at a transmitting end, in a digital signal processing module, the signal is sequentially subjected to dispersion supplementation, a cascade multimode algorithm is subjected to time domain blind equalization, frequency offset estimation is performed, phase recovery is performed, a K2-QAM signal is obtained, and then maximum likelihood sequence detection is directly performed, so that the modulated signal can be recovered.

In the embodiment, a plurality of paths of modulation signals are modulated onto a plurality of paths of optical local oscillation signals through a transmitting end to obtain a plurality of paths of signals to be synthesized, the number of the modulation signals, the number of the optical local oscillation signals and the number of the signals to be synthesized are the same, and the relationship among the modulation signals, the optical local oscillation signals and the signals to be synthesized is a one-to-one correspondence relationship; the sending end synthesizes a plurality of paths of signals to be synthesized to obtain synthesized signals, and the synthesized signals are transmitted to the receiving end through optical fibers; the receiving end detects the synthesized signal to obtain a detection result of the synthesized signal, matches a demodulation strategy according to the detection result, recovers a modulation signal from the synthesized signal according to the demodulation strategy, and avoids the high-speed DAC and the high-speed ADC from excessively depending on the high-modulation-order signal, thereby avoiding the limitation of the bandwidth on the channel capacity and simply and flexibly realizing the synthesis and detection from the low baud rate to the high baud rate.

It should be understood that the foregoing is illustrative only and is not limiting, and that in specific applications, those skilled in the art may set the invention as desired, and the invention is not limited thereto.

It should be understood that, although the steps in the flowcharts in the embodiments of the present application are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited in order and may be performed in other orders, unless explicitly stated herein. Moreover, at least some of the steps in the figures may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, the order of their execution not necessarily occurring in sequence, but may be performed alternately or alternately with other steps or at least a portion of the other steps or stages.

It should be noted that the above-described working procedure is merely illustrative, and does not limit the scope of the present invention, and in practical application, a person skilled in the art may select part or all of them according to actual needs to achieve the purpose of the embodiment, which is not limited herein.

Furthermore, it should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.

The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.

The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.

Claims

1. The optical signal spectrum synthesis method is characterized by being applied to an optical signal spectrum synthesis system, wherein the optical signal spectrum synthesis system comprises a sending end and a receiving end which are connected through an optical fiber;

the signals to be synthesized in the plurality of paths are directly coupled in power to obtain the synthesized signals, and the synthesized signals are transmitted to the receiving end through optical fibers;

the receiving end recovers the modulation signal from the synthesized signal according to a preset demodulation strategy, wherein the preset demodulation strategy comprises a symmetrical receiving strategy and an asymmetrical receiving strategy;

the sending end modulates the plurality of modulation signals onto the plurality of optical local oscillation signals to obtain a plurality of signals to be synthesized, and the method further comprises the following steps:

2. The method of claim 1, wherein the receiving end includes a digital signal processing module, and the receiving end recovers the modulated signal from the composite signal according to a preset demodulation strategy, including:

when the modulation signal of the transmitting end is not precoded, the digital signal processing module sequentially performs dispersion compensation, time domain blind equalization, frequency offset estimation and phase recovery processing on the synthesized signal to obtain a first signal;

3. The method of claim 1, wherein the receiving end recovers the modulated signal from the composite signal according to a preset demodulation strategy, further comprising:

4. The method of claim 1, wherein the receiving end comprises a digital signal processing module, a photodetector array, a low pass filter array, an analog-to-digital converter array, and an optical mixer array, and recovering the modulated signal from the composite signal according to a preset demodulation strategy comprises:

5. The method of claim 1, wherein the receiving end comprises a digital signal processing module, an optical mixer array, a photodetector array, a low pass filter array, and an analog-to-digital converter array, and wherein the receiving end recovers the modulated signal from the composite signal according to a preset demodulation strategy, further comprising:

6. The method of claim 1, wherein the receiving end comprises a digital signal processing module, an optical mixer array, a photodetector array, a bandpass filter array, an electrical mixer array, a low pass filter array, and an analog-to-digital converter array, and wherein the receiving end recovers the modulated signal from the synthesized signal according to a preset demodulation strategy, further comprising:

7. The method of claim 1, wherein the receiving end comprises a digital signal processing module, an optical mixer array, a photodetector array, a time division demultiplexer, and an analog-to-digital converter array, and wherein the receiving end recovers the modulated signal from the composite signal according to a preset demodulation strategy, further comprising:

8. An optical signal spectrum synthesis system, wherein the optical signal spectrum synthesis system comprises a transmitting end and a receiving end, the transmitting end and a receiving end are connected through an optical fiber, and the optical signal spectrum synthesis system is used for executing the optical signal spectrum synthesis method according to any one of claims 1-7.