CN113132014A - Optical interconnection communication method and system - Google Patents

Abstract

An optical interconnection communication method and system relates to the high-speed optical interconnection field in a data center, comprising: the binary bit stream signal to be transmitted is converted into an analog electric signal after being processed by the DSP; a laser is adopted to output two paths of light, one path of light is used as an optical carrier of an integrated double-offset coherent optical transmitter to modulate the analog electrical signal into a complex optical field signal, and the other path of light is used as local oscillator light to perform time delay adjustment; performing coherent mixing on the complex optical field signal and the local oscillator light through a polarization-independent coherent optical receiver, wherein the polarization state of the local oscillator light is controlled through feedback polarization disturbance, and the polarization state of the local oscillator light is prevented from falling into X and Y directions; and recovering the binary bit stream signal by DSP processing of the mixed electric signal. The invention is suitable for various modulation formats and various rates, and can also reduce the cost and the power consumption.

Description

Optical interconnection communication method and system

Technical Field

The invention relates to the field of high-speed optical interconnection in a data center, in particular to an optical interconnection communication method and system.

Background

With the advent and popularity of new, bandwidth-intensive network applications such as HDTV (High Definition video), VR (Virtual Reality), teleconferencing, mobile internet, and cloud computing, network traffic has continued to grow rapidly at a compound annual growth rate of over 22% each year. Fiber optic communication networks, as a foundation for information carrying, transmission and exchange, will also be under tremendous pressure. Particularly, in the trend of 5G about to be commercially used, the new creation of DCN (Data Center Network) and CDN (Content Delivery Network) changes the distribution of large Data traffic in the Network silently. The large data services mainly based on-line live broadcast, video transmission and file sharing occupy the main body of internet traffic, are mainly carried and distributed through DCN and CDN, and do not need to be transmitted through a long-distance network in most scenes, so that the network traffic load is transferred from a long-distance backbone network to a medium-short distance metropolitan area network and a data center. Studies have shown that 2016 global data center-related IP flows have been as high as 6.8ZB (1ZB ═ 10)⁹TB), it is expected that by 2021 it will grow to 20.6ZB, with a growth rate of approximately 2-fold over 5 years. Especially in cloud computing data centers, data traffic pressure is more significant. It is expected that by 2021, 94% of the traffic will be processed in the cloud data center, but in the data center related network, more than 70% of the traffic is terminated within the data center. It is clear that short-range (less than 2km), high-speed optical interconnect technologies will play an important role in future large data transmission and carrying.

In the face of bandwidth upgrading requirements of optical interconnection in a data center, capacity, power consumption and cost are three important consideration factors, and the international mainstream standard organization correspondingly standardizes an optical module for the data center. At present, based On a short-wavelength VCSEL (Vertical Cavity Surface Emitting Laser) and a multimode fiber, a Multi-core MPO (Multi Push On) connector is used to realize 10-transmission and 10-reception, and finally complete optical interconnection of about 100G, but the transmission distance is usually limited to about 100 meters. For large data centers, the connection scenario needs to cover 5 km. At this time, it is usually necessary to upgrade to a scheme combining a DML (direct Modulated Laser) and a single-mode fiber, and an OOK (On-Off Keying) modulation scheme is adopted, such as an MSA (Multi Source Agreement) 100G CWDM4(Coarse Wavelength Division Multiplexing) standard optical mode that can support 2km and 100G transmission, but 4 sets of transceiving equipment are required in one direction. For the next generation of interconnection requirements of about 400G and 2km, an Electro-absorption Modulated Laser (EML) is required to be adopted to replace a DML combined with a high-order PAM4(4Pulse Amplitude Modulation) Modulation technology on the basis of a single-mode optical fiber, the number of wavelengths is increased to 8, and the cost and the power consumption are remarkably increased. For subsequent further expansion and upgrade, the IMDD (Intensity Modulation Direct Detection) technology will be very important, and the module size, power consumption and cost will become challenges.

Compared with the conventional IMDD, digital coherent optical communication has become a mainstream technology for long-distance optical communication in the future due to better sensitivity, higher spectral efficiency and stronger impairment compensation capability, and has been deployed commercially on a large scale. However, the existing long-range 100G/200G coherent DWDM (Dense Wavelength Division Multiplexing) system cannot be directly used for optical interconnection in a short-range data center because the number of ports in the data center is huge and sensitive to the cost of the transceiver module. Meanwhile, the long-distance module has large power consumption and size, which further limits its application in high-density optical interconnection of data center. How to reduce the cost and power consumption of the existing coherent optical communication system is the first problem facing the coherent technology for short-distance data center optical interconnection scenarios.

Currently, there are three main categories of low-cost coherent optical communication techniques. One approach is to avoid using a high-speed Digital-to-analog converter (DAC/ADC) and a complex DSP ASIC (Digital Signal Processing chip) by using a purely analog optoelectronic Signal Processing approach, in order to reduce the cost and power consumption. However, this solution completely without the need for a DSP suffers from a large degradation in performance because it is completely unable to compensate for device bandwidth limitations and is difficult to adapt to higher order modulation formats, while low complexity, crosstalk-free polarization demultiplexing is one of its limiting factors to the application. [ Journal of Lightwave technology, Vol.35, No.21, Design of Low-Power DSP-Free Coherent Receivers for Data Center Links ]. The second category is to replace the conventional 90 ° coherent mixer with a simplified 3x3 coupler in order to reduce the cost of the fractional optical device. [ Journal of Lightwave technology, Vol.36, No.16, company of low complexity coherent receivers for UDWDM-PONs ]. The other is a self-coherent method, where the local oscillator light and the Signal light are transmitted from the transmitting end to the receiving end together, and the local oscillator light and the Signal light are separated by some methods such as space division multiplexing fan-out or polarization separation and then are subjected to coherent mixing, so that the number and cost of lasers can be reduced, and a part of DSP (Digital Signal Processing) algorithms [ optical Express, vol.21, No.2, innovative selecting-synchronous coherent detection in a 19 channel-Digital-multiplexed transmission link ] at the receiving end can be simplified. In view of the industrialization and module performance consistency, it is easy to find that a coherent optical interconnect with low cost and low power consumption based on DSP is still the most promising solution in the industry. However, in the second and third low-cost coherent systems, because high-rate DA (digital-to-analog) and AD (analog-to-digital) sampling is involved, the power consumption is high, and it is difficult to meet the power consumption requirement of the pluggable optical module in the data center. Reducing the sampling rate of the system and further simplifying the coherent DSP algorithm and the architecture are possible directions for reducing power consumption, and are difficult problems to be solved by the high-speed coherent optical interconnection technology of the data center.

As shown in fig. 1 and fig. 2, a sending-end DSP processing flow and a receiving-end DSP processing flow of the conventional coherent optical communication for long-distance transmission respectively include a sampling rate conversion part, such as the up-sampling in fig. 1 and the re-sampling in fig. 2, which not only has a complex structure, but also consumes more power due to operating at a high sampling rate (greater than the baud rate). Particularly, the computation complexity of the functions of dispersion compensation, multi-tap adaptive equalization, frequency offset estimation, phase recovery and the like at the receiving end is large and occupies most of the chip power consumption, and obviously, the traditional DSP architecture cannot be directly applied to a low-cost and low-power-consumption data center short-distance optical interconnection system. The Modulation format of the signal is common Polarization-multiplexed Phase Modulation or Amplitude-Phase Modulation, such as PDM (Polarization Division multiplexed), PSK (Phase Shift Keying), PDM-QPSK (Quadrature Phase Shift Keying), PDM-8QAM (8-ary Quadrature Amplitude Modulation), PDM-16QAM (16-ary Quadrature Amplitude Modulation), PDM-64QAM (64-ary Quadrature Amplitude Modulation), and the like.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide an optical interconnection communication method and system, which are suitable for various modulation formats and various rates and can reduce the cost and the power consumption.

To achieve the above object, in one aspect, an optical interconnection communication method is adopted, including:

the binary bit stream signal to be transmitted is converted into an analog electric signal after being processed by the DSP; a laser is adopted to output two paths of light, one path of light is used as an optical carrier of an integrated double-offset coherent optical transmitter to modulate the analog electrical signal into a complex optical field signal, and the other path of light is used as local oscillator light to perform time delay adjustment;

performing coherent mixing on the complex optical field signal and the local oscillator light through a polarization-independent coherent optical receiver, wherein the polarization state of the local oscillator light is controlled through feedback polarization disturbance, and the polarization state of the local oscillator light is prevented from falling into X and Y directions; and recovering the binary bit stream signal by DSP processing of the mixed electric signal.

Preferably, the digital signal processing of the binary bitstream signal to be transmitted includes:

after FEC coding is carried out on binary bit stream signals to be transmitted, independent constellation mapping is carried out on X, Y two polarization states to generate two independent complex signal streams, polarization diversity pre-coding is carried out, time domain pre-compensation is carried out on the pre-coded two signals after orthogonal separation, digital-to-analog conversion is carried out on the compensated signals by taking the baud rate as the sampling rate, and the analog electric signals are obtained.

Preferably, the constellation map generates a complex signal stream of [ X₁，Y₁]^TThe precoded symbol stream is [ X ]₂，Y₂]^TThe rule of precoding is [ X ]₂，Y₂]^T＝H·[X₁，Y₁]^T，

Is a precoding matrix and satisfies ad-bc ≠ 0.

Preferably, the digital signal processing of the mixed electric signal includes:

and performing analog-to-digital conversion on the mixed electric signal into a digital signal, performing anti-aliasing filtering, performing feed-forward equalization and clock synchronization on the filtered signal, performing single-tap adaptive equalization to realize polarization demultiplexing, and performing de-precoding, de-mapping and FEC decoding to obtain the binary bit stream signal.

Preferably, the two signals obtained by polarization demultiplexing are [ A ]₁，B₁]^TUsing a matrix pair [ A ]₁，B₁]^TPerforming polarization-resolving diversity pre-coding processing to obtain [ A₂,B₂]^TThe rule of the polarization diversity precoding is as follows: [ A ]₂，B₂]^T＝H‘·[A₁，B₁]^TWhere H' is the inverse of the precoding matrix H,

preferably, the controlling the polarization state of the local oscillator light by the feedback polarization comprises:

the polarization-independent coherent optical receiver divides received local oscillation light into two branches with mutually perpendicular polarization states, the local oscillation light of each branch is divided into two paths according to different power proportions, one path with smaller optical power divided by the local oscillation light of each branch is extracted, the power difference of the two extracted local oscillation lights is obtained and converted into photocurrent amplitude, and when the absolute value of the photocurrent amplitude is larger than a preset threshold value, the local oscillation light is disturbed through a control signal in direct proportion to the absolute value.

Preferably, the optical interconnection communication method is applicable to modulation formats including QPSK, 8QAM, 16QAM, 32QAM and 64 QAM;

the applicable information rates of the optical interconnection communication method comprise 100G, 200G, 400G, 600G and 800G.

In another aspect, an optical interconnection communication system is provided, including:

a laser for outputting continuous light;

the first optical splitter is used for receiving the continuous light and splitting the continuous light into two paths, wherein one path provides optical carriers and the other path serves as local oscillation light;

the transmitting DSP chip is used for converting binary bit stream signals to be transmitted into analog electric signals after the binary bit stream signals are processed by the DSP;

the integrated double-bias coherent optical transmitter is used for receiving the optical carrier and modulating the analog electric signal into a complex optical field signal;

the first optical fiber channel is used for transmitting the complex optical field signal output by the integrated double-polarization coherent optical transmitter;

the coarse adjustable delay line is used for coarsely adjusting the time delay of the local oscillator optical transmission line so as to match the length of the complex optical field signal transmission link;

the second optical fiber channel is used for transmitting the local oscillator light adjusted by the coarse adjustable delay line;

the polarization-independent coherent optical receiver is used for receiving the complex optical field signal and the local oscillator light which are transmitted by the first optical fiber channel and the second optical fiber channel respectively and performing coherent frequency mixing; the polarization-independent coherent optical receiver comprises a polarization scrambler for controlling the polarization state of the local oscillator light through feedback polarization scrambling to avoid the polarization state of the local oscillator light falling into X and Y directions;

and the receiving end DSP chip is used for receiving the electrical signals after frequency mixing and recovering the binary bit stream signals through DSP processing.

Preferably, the laser is a DFB laser; the splitting ratio of the first splitter 2 is 7: 3; the coarse adjustable delay line is realized by adopting a single mode fiber; the first optical fiber channel and the second optical fiber channel are both common single mode optical fibers.

Preferably, the polarization-independent coherent optical receiver includes:

the first polarization beam splitter is used for splitting the complex optical field signal into two branches with mutually vertical polarization states;

the fine adjustable delay line is used for accurately adjusting the transmission delay and the optical path difference of the local oscillator light relative to the signal light, and ensuring that the signal light and the local oscillator light meet the coherence length;

the second polarization beam splitter is used for splitting the local oscillator light into two branches with mutually vertical polarization states;

the polarization scrambler receives the local oscillation light adjusted by the fine adjustable delay line, controls the polarization state of the local oscillation light input to the second polarization beam splitter, and avoids the local oscillation light entering the second polarization beam splitter from being in the horizontal or vertical direction;

the second optical splitter and the third optical splitter are used for splitting the two local oscillator lights with polarization states in different power proportions;

the fifth balance detector is used for receiving one path of local oscillator light with smaller power respectively split by the second optical splitter and the third optical splitter, obtaining a power difference and converting the power difference into photocurrent amplitude output;

the controller is used for converting the photocurrent amplitude into a disturbance control signal of the local oscillation light polarization state and controlling the deflector;

and the frequency mixing gain module is used for performing coherent frequency mixing on the two paths of complex optical field signals output by the first polarization beam splitter and one path of local oscillator light with higher power, which is split by the second beam splitter and the third beam splitter, respectively obtaining a real part and an imaginary part of X, Y polarization, amplifying and realizing automatic gain control.

Preferably, the mixing gain module includes:

the first 90-degree frequency mixer is used for carrying out coherent frequency mixing on one path of complex optical field signals output by the first polarization beam splitter and one path of local oscillator light with larger power split by the second beam splitter;

the second 90-degree frequency mixer is used for carrying out coherent frequency mixing on the other path of complex optical field signals output by the first polarization beam splitter and one path of local oscillator light which is split by the third beam splitter and has larger power;

the first balanced detector and the second balanced detector are used for converting the optical signal output by the first 90-degree mixer into an electric signal to respectively obtain a real part and an imaginary part of the X polarization;

the third balanced detector and the fourth balanced detector are used for converting the optical signal output by the second 90-degree mixer into an electric signal to respectively obtain a real part and an imaginary part of Y polarization;

and the transimpedance amplifier is used for amplifying the real part and the imaginary part of the X polarization and the real part and the imaginary part of the Y polarization and realizing automatic gain control.

Preferably, the second optical splitter and the third optical splitter have the same ratio, which is 95: 5;

and when the absolute value of the amplitude of the photocurrent output by the fifth balance detector is greater than a preset threshold value, outputting a control electric signal which is in direct proportion to the absolute value to act on the polarization scrambler, wherein the threshold value is 90% of the maximum photocurrent detected by the fifth balance detector.

Preferably, the originating DSP chip includes:

the FEC encoding module is used for carrying out FEC encoding on the binary bit stream signal to be transmitted;

a constellation mapping module for performing independent constellation mapping respectively for X, Y two polarization states according to a preset modulation format to generate two independent pathsVertical complex signal stream [ X ]₁，Y₁]^T；

A pre-coding module for applying the complex signal stream [ X₁，Y₁]^TPerforming polarization hierarchical precoding to output two precoded symbol streams [ X ]₂，Y₂]^TThe precoding rule is:

[X₂，Y₂]^T＝H·[X₁，Y₁]^T，

for the precoding matrix, it satisfies ad-bc ≠ 0.

The pre-compensation module is used for performing time domain pre-compensation on the two paths of signals after pre-coding after orthogonal separation;

and the DAC module is used for performing digital-to-analog conversion on the compensated signal by taking the baud rate as the sampling rate to obtain the analog electric signal.

Preferably, the receiving DSP chip includes:

an ADC module for converting the mixed electrical signal into a digital signal;

two low-pass filters for performing anti-aliasing filtering processing on the X-polarization signal and the Y-polarization signal respectively,

the two feedforward equalizers respectively correspond to one low-pass filter and carry out feedforward equalization on the filtered signals;

two clock recovery modules, which recover the best sampling clock and phase of each feedforward equalized signal;

the self-adaptive equalization module performs self-adaptive equalization on the signals after clock recovery to realize polarization demultiplexing to obtain two paths of equalized signals [ A ]₁，B₁]^T。

A de-precoding module using a matrix pair [ A ]₁，B₁]^TPerforming polarization-resolving diversity pre-coding processing to obtain [ A₂，B₂]^TThe rule of the polarization diversity precoding is as follows: [ A ]₂，B₂]^T＝H‘·[A₁，B₁]^TWherein H' is an inverse matrix of the precoding matrix H;

two constellation diagram mapping modules, which respectively de-map the signals after de-polarization diversity pre-coding;

and the two FEC decoding modules are used for respectively carrying out FEC decoding on the binary bit after demapping and recovering the binary bit stream signal.

Preferably, the precompensation module of the originating DSP chip performs time domain precompensation by using a real number domain finite impulse response filter, and the number of taps of the finite impulse response filter is less than or equal to 3;

the self-adaptive equalization module of the receiving end DSP chip adopts a single-tap 2x2 complex butterfly filter to carry out self-adaptive equalization;

the DAC module and the ADC module both work at a sampling rate of 1 baud rate.

The technical scheme has the following beneficial effects:

compared with the prior art, the invention adopts the self-coherent technology to avoid the receiving end from adopting an expensive narrow linewidth laser and only uses one transmitting end, thereby reducing the cost of the short-distance optical interconnection system.

Further, a DFB (Distributed Feedback Laser) Laser is adopted at the transmitting end, the linewidth of the DFB Laser is generally large and is MHz-level, and the price of the DFB Laser is cheaper than that of an ECL (External Cavity Laser), the ECL is generally a narrow linewidth Laser, and the linewidth is KHz-level. However, the current commercial coherent optical communication system needs an ECL laser with a frequency of about 100kHz, so that the DFB laser is adopted to further reduce the system cost compared with other lasers.

The polarization state of the local oscillator light is controlled by adopting a mode of combining the power balance detection and the polarization scrambler, so that the risk of demodulation failure when the local oscillator light is just X or Y polarized is avoided, the polarization-independent coherent reception is realized, and the difficulty of controlling the polarization state of the local oscillator light in an auto-coherent system is solved.

The optical path difference of the local oscillator light and the signal light is adjusted by adopting a coarse adjustable delay line and a fine adjustable delay line on the optical path, and the matching of the coherent length is ensured, so that the frequency offset estimation and the phase recovery at a receiving end are avoided, and a DSP algorithm and a circuit at the receiving end are simplified to the maximum extent.

On the aspect of DSP, on one hand, DAC and ADC conversion of baud rate sampling rate is adopted, so that the power consumption of a coherent DSP chip is reduced to a great extent; on the other hand, by providing a set of very simple DSP signal processing flow at the transmitting and receiving end, the complexity of the DSP is simplified, and the power consumption and the area of a chip are saved.

Polarization diversity precoding is utilized in a transmitting-end DSP chip, correlation is artificially introduced between signals in two polarization states, tolerance to polarization correlation loss is expected to be improved, and the problem of performance loss of a low-cost device in a coherent system is solved to a certain extent.

In a receiving end DSP chip, FFE (feed Forward Equalizer) is used for compensating problems of optical fiber dispersion and ISI (Inter Symbol Interference) caused by device bandwidth limitation, then a single-tap butterfly filter is used for realizing polarization demultiplexing, then precoding is removed, and symbols in X and Y polarization states are recovered. Compared with the traditional coherent DSP algorithm, the whole DSP algorithm is greatly simplified, and all algorithm sub-modules work under the condition of single sampling rate, so that the power consumption of the DSP chip is expected to be greatly reduced.

Moreover, based on the DSP processing of the transmitting end, different high-order modulation formats such as QPSK, 8QAM, 16QAM, 32QAM, 64QAM and the like can be suitable, and meanwhile, the method is suitable for multiple information rates such as 100G, 200G, 400G, 600G, 800G and the like.

In conclusion, the invention has the beneficial effects that the short-distance optical interconnection with low cost, high speed and low power consumption can be realized, and the invention is very suitable for the optical interconnection scene in the data center sensitive to cost and power consumption.

Drawings

Fig. 1 is a schematic diagram illustrating a processing flow of an originating DSP of a conventional coherent optical communication for long-distance transmission;

FIG. 2 is a diagram illustrating a DSP processing flow at a receiving end of a conventional coherent optical communication for long-distance transmission;

FIG. 3 is a diagram illustrating a single tap adaptive equalizer according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an optical interconnect communication system according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an implementation of a polarization independent coherent optical receiver;

FIG. 6 is a diagram of an originating DSP chip according to an embodiment of the present invention;

FIG. 7 is a diagram of a receiving DSP chip according to an embodiment of the present invention;

FIG. 8 is a flow chart of local oscillator light polarization control according to an embodiment of the present invention;

FIG. 9 is a QPSK constellation according to an embodiment of the present invention;

fig. 10 is a constellation diagram of 8QAM according to an embodiment of the present invention.

Reference numerals:

1-a laser, 2-a first optical splitter, 3-a coarse adjustable delay line, 4-an integrated double-polarization coherent optical transmitter, 5-a sending end DSP chip, 6-a first optical fiber channel, 7-a polarization-independent coherent optical receiver, 8-a receiving end DSP chip and 9-a second optical fiber channel;

the device comprises a 51-FEC encoding module, a 52-constellation mapping module, a 53-precoding module, a 54-precompensation module and a 55-DAC module;

700-frequency mixing gain module, 701-first polarization beam splitter, 702-first 90 ° frequency mixer, 703-first balanced detector, 704-second balanced detector, 705-transimpedance amplifier, 706-second 90 ° frequency mixer, 707-third balanced detector, 708-fourth balanced detector, 709-second light splitter, 710-third light splitter, 711-second polarization beam splitter, 712-fifth balanced detector, 713-controller, 714-polarization scrambler, 715-fine adjustable delay line;

81-ADC module, 82-low pass filter, 83-feedforward equalizer, 84-clock recovery module, 85-adaptive equalization module, 86-de-precoding module, 87-constellation diagram mapping module and 88-FEC decoding module.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

An embodiment of an optical interconnection communication method is provided, which specifically includes:

in the transmitting direction, the binary bit stream signal to be transmitted is converted into an analog electrical signal after being processed by the DSP. A laser provides a direct current optical carrier for optical interconnection communication, and the direct current optical carrier is also used as local oscillator light for coherent detection. Specifically, a laser is adopted to output two paths of light, wherein one path of light is used as an optical carrier of an integrated double-bias coherent optical transmitter, and an analog electric signal obtained by DSP processing is modulated into a complex optical field signal; and the other path is used as local oscillation light for time delay adjustment. The time delay of the local oscillator optical transmission line can be roughly adjusted through the rough adjustable time delay line so as to match the length of the complex optical field signal transmission link and ensure that the complex optical field signal and the local oscillator light are close to the coherence length.

In the receiving direction, the complex optical field signal and the local oscillator light are received through a polarization-independent coherent optical receiver, coherent mixing is carried out, and the modulation signal is moved to a baseband to obtain a baseband electric signal. The polarization state of the local oscillator light is controlled through the feedback polarization disturbance, the polarization state of the local oscillator light is prevented from falling into the X direction and the Y direction, data loss in one polarization state is further caused, and correct demodulation of polarization multiplexing data is guaranteed. The mixed electrical signal is processed by the DSP to recover a binary bit stream signal. Wherein, four paths of electric signals are obtained after frequency mixing, namely two paths of electric signals of X polarization and Y polarization, and the respective in phase and quadrature.

The above controlling the polarization state of the local oscillator light by feeding back the polarization disturbance specifically includes: the polarization-independent coherent optical receiver divides received local oscillation light into two branches with mutually perpendicular polarization states, the local oscillation light of each branch is divided into two branches according to different power proportions, one branch with smaller optical power divided by the local oscillation light of each branch is extracted, the power difference of the two extracted local oscillation lights is obtained and converted into photocurrent amplitude, and when the absolute value of the photocurrent amplitude is larger than a preset threshold value, the local oscillation light is disturbed through a control signal in direct proportion to the absolute value.

Based on the above embodiments, an embodiment of DSP processing in the transmit direction and the receive direction is further provided. The binary bit stream signal to be transmitted is processed by a digital signal, specifically comprising the steps of:

s101, performing FEC (Forward Error Correction) coding on a binary bit stream signal to be transmitted.

S102, according to a preselected modulation format, the data subjected to FEC coding are subjected to independent constellation mapping respectively aiming at X, Y two polarization states (namely a horizontal polarization state and a vertical polarization state) to generate two independent complex signal streams [ X ]₁，Y₁]^T。

S103. complex signal stream [ X ]₁，Y₁]^TThen, polarization diversity pre-coding is carried out to output two pre-coded symbol streams [ X ]₂，Y₂]^T(ii) a The precoding rule is:

[X₂，Y₂]^T＝H·[X₁，Y₁]^Twherein, in the step (A),

is a precoding matrix and satisfies ad-bc ≠ 0.

S104, performing orthogonal separation on the two paths of signals after precoding to obtain four corresponding paths of signals, representing the real part and the imaginary part of the X and Y polarization states respectively, and performing time domain pre-compensation through a real Impulse Response (FIR) filter respectively to adjust the relative time delay between the signals and compensate the bandwidth of part of photoelectric devices.

Preferably, to ensure low complexity and power consumption, the number of FIR taps is no more than 3.

And S105, sending the four pre-compensated signals into a DAC (digital-to-analog converter), and performing digital-to-analog conversion by taking the baud rate as a sampling rate to obtain an electric signal to be modulated.

In the receiving direction, the digital signal processing of the mixed electrical signal specifically comprises the following steps:

s201, four paths of electric signals output by the polarization-independent coherent receiver are subjected to analog-to-digital conversion by taking the baud rate as the sampling rate to obtain four paths of digital signals.

S202, performing digital anti-aliasing filtering processing on the four paths of digital signals by using a low-pass filter to remove signal spectrum aliasing possibly caused by single-time sampling.

S203, performing feed-forward equalization on the filtered signals to compensate the influence of intersymbol interference (ISI) caused by bandwidth limitation and short-distance optical fiber dispersion, and also compensating the time difference between channels;

and S204, performing clock synchronization on the signals subjected to the feedforward equalization to recover the optimal sampling clock and phase, wherein the clock synchronization algorithm needs to work at a single sampling rate.

S205. as shown in fig. 3, Xin, Yin, Xin 'and Yin' respectively represent input and output signal vectors of the adaptive equalizer X, Y in two polarization states, Wxx, Wxy, Wyx and Wyy are four groups of tap coefficients of the butterfly filter, respectively represent the influence of the X-polarization input on the X-polarization output, the influence of the Y-polarization input on the X-polarization output, the influence of the X-polarization input on the Y-polarization output, and the influence of the Y-polarization input on the Y-polarization output. According to a certain tap self-adaptive updating criterion and updating period, single-tap self-adaptive equalization is carried out to realize polarization demultiplexing, and two equalized signals are obtained as [ A ]₁，B₁]^T。

Preferably, the clock-recovered signal is adaptively equalized using a single-tap adaptive filter, such as a single-tap 2x2 complex butterfly filter.

S206. use a matrix pair [ A ]₁，B₁]^TPerforming polarization-resolving diversity pre-coding processing to obtain [ A₂，B₂]^TThe rule for de-polarization diversity precoding is as follows: [ A ]₂，B₂]^T＝H‘·[A₁，B₁]^TWhere H' is the inverse of the precoding matrix H,

s207, according to the preselected modulation format, the demapping of the signal after the precoding is removed is completed, and the recovered symbols are changed into binary bits.

And S208, FEC decoding is carried out on the binary bit after demapping, and the binary data stream of the sending end is recovered.

Preferably, the number of taps used in the feed-forward equalization in S205 is not greater than 10, and the tap adaptive update criterion may be a Constant Modulus Algorithm (CMA), a multi-modulus algorithm (MMA), a cascaded multi-modulus algorithm (CMMA), or a least mean square error algorithm (LMS). The tap coefficient update period of the single-tap adaptive filter is not less than every 10 symbol periods.

As shown in fig. 4, the present invention further provides an embodiment of an optical interconnection communication system, which can implement at least one of the above-mentioned methods. The system comprises a transmitting end and a receiving end, wherein the transmitting end comprises a laser 1, a first optical splitter 2, a coarse adjustable delay line 3, an integrated double-polarization coherent optical transmitter 4, a transmitting end DSP chip 5, a first optical fiber channel 6 and a second optical fiber channel 9; the receiving end comprises a polarization-independent coherent optical receiver 7 and a receiving end DSP chip 8; the transmitting end and the receiving end are transmitted through two optical fiber channels.

The output of the laser 1 is connected with the first optical splitter 2, the output of the first optical splitter 2 is respectively connected with the integrated double-polarization coherent optical transmitter 4 and the coarse adjustable delay line 3, and the integrated double-polarization coherent optical transmitter 4 is also connected with the originating DSP chip 5 and the first optical fiber channel 6. The other port of the coarse adjustable delay line 3 is connected to a second fibre channel 9. The other ends of the first optical fiber channel 6 and the second optical fiber channel 9 are respectively connected to a signal light and a local oscillation light interface of the polarization-independent coherent light receiver 7; and the output electrical interface of the polarization-independent coherent optical receiver 7 is connected with the receiving end DSP chip.

The laser 1 is used for outputting continuous light, providing a direct current optical carrier for an optical interconnection system, and simultaneously serving as local oscillation light for coherent detection. Preferably, the laser 1 has a line width of not less than 10 MHz. The laser 1 is preferably a DFB (Distributed Feedback laser).

The first optical splitter 2 is configured to split the output of the laser 1 into two paths, and control the distribution ratio of optical carrier and local oscillation optical power. Preferably, the splitting ratio of the first splitter 2 is greater than 6: 4, less than 8: 2.

the originating DSP chip 5 is used to convert the binary bitstream signal to be transmitted into an analog electrical signal after encoding, constellation mapping and appropriate pre-compensation, for driving the integrated double-offset coherent optical transmitter 4. The DAC used in the originating DSP chip 5 operates at a sampling rate of 1 baud rate to reduce the system power consumption.

The integrated double-polarization coherent optical transmitter 4 is used for modulating the analog electrical signal into a polarization-multiplexed complex optical field signal, i.e., signal light, and completing the conversion of the signal to be transmitted from an electrical domain to an optical field.

The first optical fiber channel 6 serves as a low-loss transmission medium for transmitting the modulated signal light.

The coarse adjustable delay line 3 is used for roughly adjusting the delay of the local oscillator optical transmission line to match the optical signal transmission link length and ensure that the signal light and the local oscillator light are close to the coherence length.

The second optical fiber channel 9 is used as a low-loss transmission medium for transmitting the local oscillation optical signal adjusted by the coarse adjustable delay line 3.

Further, the lengths of the first fibre channel 6 and the second fibre channel 9 are substantially equal and do not exceed 5 km.

The polarization-independent coherent optical receiver 7 is configured to perform coherent mixing on the local oscillator light and the signal light, and shift the modulated signal to a baseband to obtain a baseband electrical signal. Further, the polarization-independent coherent optical receiver 7 implements feedback polarization disturbance, thereby automatically adapting to local oscillation light input in any polarization state.

The receiving-end DSP chip 8 is configured to convert the received baseband electrical signal into a digital signal, perform certain digital signal processing, such as damage equalization and compensation, polarization demultiplexing, demodulation and decoding, and finally restore the binary data stream of the transmitting end. The ADC of the receive DSP chip 8 also operates at a sampling rate of 1 baud rate to reduce the system power consumption.

As shown in fig. 5, an embodiment of the polarization independent coherent optical receiver 7 in the foregoing embodiment is provided, and its internal structure specifically includes a first polarization beam splitter 701, a second beam splitter 709, a third beam splitter 710, a second polarization beam splitter 711, a fifth balanced detector 712, a controller 713, a polarization scrambler 714, a fine tunable delay line 715, and a mixer gain module 700. The mixing gain block 700 is composed of a first 90 ° mixer 702, a first balanced detector 703, a second balanced detector 704, a transimpedance amplifier 705, a second 90 ° mixer 706, a third balanced detector 707, and a fourth balanced detector 708.

The input of the first polarization beam splitter 701 is used as a signal light input port of the polarization-independent coherent light receiver 7, one end of the fine tunable delay line 715 is used as a local oscillation light input port of the polarization-independent coherent light receiver 7, and the output of the transimpedance amplifier 705 is used as an electrical signal output port of the polarization-independent coherent light receiver 7.

Two outputs of the first polarization beam splitter 701 are connected to one input port of the first 90 ° mixer 702 and the second 90 ° mixer 706, respectively; one of the output ports of the second optical splitter 709 and the second optical splitter 710 is connected to the other input port of the first 90 ° hybrid 702 and the second 90 ° hybrid 706, respectively. The four outputs of the first 90 ° mixer 702 are connected to the input ports of a first balanced detector 703 and a second balanced detector 704, respectively. The four outputs of the second 90 ° hybrid 706 are connected to the input ports of a third balanced detector 707 and a fourth balanced detector 708, respectively. The outputs of the first balanced detector 703, the second balanced detector 704, the third balanced detector 707 and the fourth balanced detector 708 are connected to the transimpedance amplifier 705.

The second polarizing beamsplitter 711 has an input coupled to the output of the polarization scrambler 714, and two outputs coupled to the inputs of the second and third beamsplitters 709 and 710, respectively. The other output ports of the second optical splitter 709 and the third optical splitter 710 are connected to the input of a fifth balanced detector 712. The output of the fifth balanced detector 712 is connected to an input of a controller 713, the output of the controller 713 is connected to a control port of a polarization scrambler 714, and the input of the polarization scrambler 714 is connected to the output of a fine adjustable delay line 715.

The fine adjustable delay line 715 is used to accurately adjust the transmission delay and the optical path difference between the two optical paths of the local oscillator light and the signal light in a small range, so as to ensure that the signal light and the local oscillator light meet the coherence length.

The first polarization beam splitter 701 is used to split a complex optical field signal (i.e., signal light) into two branches with mutually perpendicular polarization states.

The second polarization beam splitter 711 is configured to split the local oscillation light into two branches with mutually perpendicular polarization states.

The polarization scrambler 714 is configured to control a polarization state of the local oscillation light input to the second polarization beam splitter 711, so as to prevent the polarization state of the local oscillation light entering the second polarization beam splitter 711 from falling into X and Y directions, that is, prevent the local oscillation light from being exactly in a horizontal or vertical direction.

The second optical splitter 709 and the third optical splitter 710 are configured to split two local oscillator lights with polarization states in different power proportions, and the path with the smaller power is sent to the fifth balanced detector 712.

The fifth balance detector 712 is configured to receive a path of local oscillator light with smaller power respectively split by the second optical splitter and the third optical splitter, extract a power difference between the local oscillator light after polarization splitting, and convert the local oscillator light into a photocurrent amplitude for output.

The controller 713 is configured to convert the photocurrent amplitude into a disturbance control signal of the local oscillation polarization state, and control the polarization scrambler 714 in a certain manner to implement polarization disturbance.

The frequency mixing gain module 700 is configured to perform coherent frequency mixing on the two paths of complex optical field signals output by the first polarization beam splitter 701 and the one path of local oscillator light with higher power split by the second optical splitter 709 and the third optical splitter 711 respectively to obtain a real part and an imaginary part of X, Y polarization respectively, perform amplification, and implement automatic gain control. Further, the specific functions of the internal structure are as follows:

the first 90 ° mixer 702 is configured to perform coherent mixing on one path of complex optical field signals output by the first polarization beam splitter 701 and one path of local oscillator light with larger power split by the second optical splitter 709.

The second 90 ° mixer 706 is configured to perform coherent mixing on the other path of complex optical field signal output by the first polarization beam splitter 701 and one path of local oscillator light with larger power split by the third optical splitter 710.

A first balanced detector 703 and a second balanced detector 704 for converting the optical signal output from the first 90 ° mixer 702 into an electrical signal, and obtaining the real part and the imaginary part of the X-polarization, respectively.

A third balanced detector 707 and a fourth balanced detector 708 for converting the optical signal output by the second 90 ° hybrid 706 into an electrical signal, resulting in a real part and an imaginary part of the Y polarization, respectively.

The transimpedance amplifier 705 amplifies both the real part and the imaginary part of the X polarization and the real part and the imaginary part of the Y polarization, and performs automatic gain control.

The polarization independent coherent optical receiver 7 implements feedback polarization disturbance by detecting the differential power signals of the second optical splitter 709 and the third optical splitter 710, thereby automatically adapting to local oscillation light input in any polarization state.

As shown in fig. 6, the process of the controller 713 controlling the polarization scrambler 714 according to a certain manner specifically includes:

s301, the fifth balanced detector 712 detects the optical power difference of the local oscillator light with smaller output power of the third optical splitter 709 and the fourth optical splitter 710, and converts the optical power difference into photocurrent amplitude output.

S302, taking the absolute value of the amplitude of the photocurrent output by the fifth balanced detector 712.

S303, the controller 713 judges whether the absolute value is larger than a preset threshold value, if so, the process goes to S304; if not, go back to S301. Preferably, the threshold is 90% of the maximum photocurrent detected by the fifth balanced detector 712.

S304, the controller 713 outputs a control electrical signal proportional to the absolute value to the scrambler 714.

S305, the polarization scrambler 714 scrambles the polarization state of the input local oscillation light according to the size of the received control electric signal.

In the optical interconnection communication system, preferably, the laser 1 is a DFB laser, the nominal line width is 10MHz, and the optical power is 16 dBm. The splitting ratio of the first splitter 2 is 7: 3. the coarse tunable delay line 3 is implemented by using a single mode fiber of 1 to 5 meters. The first optical fiber channel 6 and the second optical fiber channel 9 are both common single mode optical fibers, and the length is 2 kilometers. The second optical splitter 709 and the third optical splitter 710 have the same proportion, which is 95: 5.

as shown in fig. 7, an embodiment of an originating DSP chip 5 in an optical interconnect communication system is provided. The originating DSP chip 5 specifically includes an FEC encoding module 51, a constellation mapping module 52, a pre-encoding module 53, a pre-compensation module 54, and a DAC module 55.

The FEC encoding module 51 is configured to FEC encode the binary bitstream signal to be transmitted.

The constellation mapping module 52 is configured to perform independent constellation mapping for X, Y two polarization states according to a preset modulation format, and generate two independent complex signal streams [ X₁，Y₁]^T。

The pre-coding module 53 is used to convert the complex signal stream [ X₁，Y₁]^TPerforming polarization hierarchical precoding to output two precoded symbol streams [ X ]₂，Y₂]^TThe precoding rule is:

[X₂，Y₂]^T＝H·[X₁，Y₁]^T，

for the precoding matrix, it satisfies ad-bc ≠ 0.

The pre-compensation module 54 is configured to orthogonally separate the two pre-coded signals to obtain four corresponding signals, which respectively represent the real part and the imaginary part of the X and Y polarization states, and then perform time domain pre-compensation to adjust the relative time delay between the signals and compensate the bandwidth of part of the photoelectric devices. Preferably, the pre-compensation module 54 performs time-domain pre-compensation by using a real number domain Finite Impulse Response (FIR) filter; to ensure low complexity and power consumption, the number of FIR taps is no more than 3.

The DAC module 55 is configured to perform digital-to-analog conversion on the compensated signal at a sampling rate of 1 baud rate to obtain an analog electrical signal.

As shown in fig. 8, the receiving DSP chip 8 includes an ADC module 81, two low pass filters 82, two feed forward equalizers 83, two clock recovery modules 84, an adaptive equalization module 85, a de-precoding module 86, two constellation diagram mapping modules 87, and two FEC decoding modules 88.

The ADC block 81 is configured to convert the four electrical signals output by the polarization independent coherent receiver 7 into four digital signals at a sampling rate of 1 baud rate.

Two low-pass filters 82 for performing anti-aliasing filtering processing on the X-polarization signal and the Y-polarization signal, respectively, to remove signal spectrum aliasing possibly caused by single-time sampling.

Two feedforward equalizers 83, each corresponding to one of the low-pass filters 82, for performing feedforward equalization on the filtered signals; to compensate for the effects of intersymbol interference (ISI) due to system bandwidth limitations and short-range fiber dispersion, and also to compensate for time differences between channels.

Two clock recovery modules 84, which recover the best sampling clock and phase of each feed-forward equalized signal; the clock synchronization algorithm needs to operate at a single sample rate.

A self-adaptive equalization module 85, configured to perform self-adaptive equalization on the clock-recovered signal, implement polarization demultiplexing, and obtain two equalized signals [ a₁，B₁]^T。

A de-precoding module 86 using a matrix pair [ A ]₁，B₁]^TPerforming polarization-resolving diversity pre-coding processing to obtain [ A₂，B₂]^TThe rule for solving the polarization diversity precoding is as follows: [ A ]₂，B₂]^T＝H‘·[A₁，B₁]^TWhere H' is the inverse of the precoding matrix H.

Two constellation mapping modules 87, each demapping the signal that has been demapped and encoded.

And two FEC decoding modules 88 for FEC decoding the demapped binary bits respectively to recover the binary bit stream signal.

Based on the above system, an embodiment of the use of DSP processing is provided. In this embodiment, the baud rate is 32Gbaud, the adopted modulation format is polarization multiplexing QPSK, that is, PDM-QPSK signal, and the constellation diagram and bit mapping manner thereof are shown in fig. 9. Polarization diversity precoding matrix is

The number of taps used by the feedforward equalizer 83 is 7, the adaptive equalization module 85 uses a single-tap adaptive filter, the tap adaptive update is quasi-cascaded multi-mode algorithm (CMMA), and the tap coefficient update period is equal to every 32 symbol periods.

Based on the above system, another embodiment of the use of DSP processing is provided. In this embodiment, the baud rate is 42Gbaud, the adopted modulation format is polarization multiplexing 8QAM, that is, PDM-8QAM signals, and the constellation diagram and the bit mapping mode thereof are shown in fig. 10. Fig. 10 shows a special 8QAM, which is a subset of 16QAM constellation points, which is distinguished from the usual square or circular 8QAM because its minimum euclidean distance is the largest, and thus has better BER performance under AWGN. The bit-to-symbol mapping specifies a uniquely defined correspondence of binary bits to complex signal symbols. Polarization diversity precoding matrix is

The number of taps used in feed-forward equalization is 9, the tap adaptive update of the single-tap adaptive filter is quasi-multimode algorithm (MMA), and the tap coefficient update period is equal to 16 symbol periods.

The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.

Claims (15)

1. An optical interconnect communication method, comprising:

the binary bit stream signal to be transmitted is converted into an analog electric signal after being processed by the DSP; a laser is adopted to output two paths of light, one path of light is used as an optical carrier of an integrated double-offset coherent optical transmitter to modulate the analog electrical signal into a complex optical field signal, and the other path of light is used as local oscillator light to perform time delay adjustment;

performing coherent mixing on the complex optical field signal and the local oscillator light through a polarization-independent coherent optical receiver, wherein the polarization state of the local oscillator light is controlled through feedback polarization disturbance, and the polarization state of the local oscillator light is prevented from falling into X and Y directions; and recovering the binary bit stream signal by DSP processing of the mixed electric signal.

2. The optical interconnect communication method of claim 1, wherein the binary bitstream signal to be transmitted is digitally signal processed comprising:

after FEC coding is carried out on binary bit stream signals to be transmitted, independent constellation mapping is carried out on X, Y two polarization states to generate two independent complex signal streams, polarization diversity pre-coding is carried out, time domain pre-compensation is carried out on the pre-coded two signals after orthogonal separation, digital-to-analog conversion is carried out on the compensated signals by taking the baud rate as the sampling rate, and the analog electric signals are obtained.

3. The optical interconnect communication method of claim 2, wherein: the complex signal stream generated by the constellation map is [ X ]₁，Y₁]^TThe precoded symbol stream is [ X ]₂，Y₂]^TThe rule of precoding is [ X ]₂，Y₂]^T＝H·[X₁，Y₁]^T，

Is a precoding matrix and satisfies ad-bc ≠ 0.

4. The optical interconnect communication method of claim 3, wherein the digital signal processing of the mixed electrical signal comprises:

and performing analog-to-digital conversion on the mixed electric signal into a digital signal, performing anti-aliasing filtering, performing feed-forward equalization and clock synchronization on the filtered signal, performing single-tap adaptive equalization to realize polarization demultiplexing, and performing de-precoding, de-mapping and FEC decoding to obtain the binary bit stream signal.

5. The optical interconnect communication method of claim 4, wherein: the two paths of signals obtained by polarization demultiplexing are [ A ]₁，B₁]^TUsing a matrix pair [ A ]₁，B₁]^TPerforming polarization-resolving diversity pre-coding processing to obtain [ A₂，B₂]^TThe rule of the polarization diversity precoding is as follows: [ A ]₂，B₂]^T＝H‘·[A₁，B₁]^TWhere H' is the inverse of the precoding matrix H,

6. the optical interconnect communication method of claim 1, wherein the controlling the polarization state of the local oscillator light by the feedback polarization comprises:

the polarization-independent coherent optical receiver divides received local oscillation light into two branches with mutually perpendicular polarization states, the local oscillation light of each branch is divided into two paths according to different power proportions, one path with smaller optical power divided by the local oscillation light of each branch is extracted, the power difference of the two extracted local oscillation lights is obtained and converted into photocurrent amplitude, and when the absolute value of the photocurrent amplitude is larger than a preset threshold value, the local oscillation light is disturbed through a control signal in direct proportion to the absolute value.

7. The optical interconnect communication method according to any one of claims 1 to 6, wherein:

the optical interconnection communication method is applicable to modulation formats including QPSK, 8QAM, 16QAM, 32QAM and 64 QAM;

the applicable information rates of the optical interconnection communication method comprise 100G, 200G, 400G, 600G and 800G.

8. An optical interconnect communication system, comprising:

a laser for outputting continuous light;

the first optical splitter is used for receiving the continuous light and splitting the continuous light into two paths, wherein one path provides optical carriers and the other path serves as local oscillation light;

the transmitting DSP chip is used for converting binary bit stream signals to be transmitted into analog electric signals after the binary bit stream signals are processed by the DSP;

the integrated double-bias coherent optical transmitter is used for receiving the optical carrier and modulating the analog electric signal into a complex optical field signal;

the first optical fiber channel is used for transmitting the complex optical field signal output by the integrated double-polarization coherent optical transmitter;

the coarse adjustable delay line is used for coarsely adjusting the time delay of the local oscillator optical transmission line so as to match the length of the complex optical field signal transmission link;

the second optical fiber channel is used for transmitting the local oscillator light adjusted by the coarse adjustable delay line;

the polarization-independent coherent optical receiver is used for receiving the complex optical field signal and the local oscillator light which are transmitted by the first optical fiber channel and the second optical fiber channel respectively and performing coherent frequency mixing; the polarization-independent coherent optical receiver comprises a polarization scrambler for controlling the polarization state of the local oscillator light through feedback polarization scrambling to avoid the polarization state of the local oscillator light falling into X and Y directions;

and the receiving end DSP chip is used for receiving the electrical signals after frequency mixing and recovering the binary bit stream signals through DSP processing.

9. The optical interconnect communication system of claim 8, wherein: the laser is a DFB laser; the splitting ratio of the first splitter 2 is 7: 3; the coarse adjustable delay line is realized by adopting a single mode fiber; the first optical fiber channel and the second optical fiber channel are both common single mode optical fibers.

10. The optical interconnect communication system of claim 8, wherein the polarization independent coherent optical receiver comprises:

the first polarization beam splitter is used for splitting the complex optical field signal into two branches with mutually vertical polarization states;

the fine adjustable delay line is used for accurately adjusting the transmission delay and the optical path difference of the local oscillator light relative to the signal light, and ensuring that the signal light and the local oscillator light meet the coherence length;

the second polarization beam splitter is used for splitting the local oscillator light into two branches with mutually vertical polarization states;

the polarization scrambler receives the local oscillation light adjusted by the fine adjustable delay line, controls the polarization state of the local oscillation light input to the second polarization beam splitter, and avoids the local oscillation light entering the second polarization beam splitter from being in the horizontal or vertical direction;

the second optical splitter and the third optical splitter are used for splitting the two local oscillator lights with polarization states in different power proportions;

the fifth balance detector is used for receiving one path of local oscillator light with smaller power respectively split by the second optical splitter and the third optical splitter, obtaining a power difference and converting the power difference into photocurrent amplitude output;

the controller is used for converting the photocurrent amplitude into a disturbance control signal of the local oscillation light polarization state and controlling the deflector;

and the frequency mixing gain module is used for performing coherent frequency mixing on the two paths of complex optical field signals output by the first polarization beam splitter and one path of local oscillator light with higher power, which is split by the second beam splitter and the third beam splitter, respectively obtaining a real part and an imaginary part of X, Y polarization, amplifying and realizing automatic gain control.

11. The optical interconnect communication system of claim 10, wherein the mixing gain module comprises:

the first 90-degree frequency mixer is used for carrying out coherent frequency mixing on one path of complex optical field signals output by the first polarization beam splitter and one path of local oscillator light with larger power split by the second beam splitter;

the second 90-degree frequency mixer is used for carrying out coherent frequency mixing on the other path of complex optical field signals output by the first polarization beam splitter and one path of local oscillator light which is split by the third beam splitter and has larger power;

the first balanced detector and the second balanced detector are used for converting the optical signal output by the first 90-degree mixer into an electric signal to respectively obtain a real part and an imaginary part of the X polarization;

the third balanced detector and the fourth balanced detector are used for converting the optical signal output by the second 90-degree mixer into an electric signal to respectively obtain a real part and an imaginary part of Y polarization;

and the transimpedance amplifier is used for amplifying the real part and the imaginary part of the X polarization and the real part and the imaginary part of the Y polarization and realizing automatic gain control.

12. The optical interconnect communication system of claim 10, wherein:

the second optical splitter and the third optical splitter have the same proportion, and are both 95: 5;

and when the absolute value of the amplitude of the photocurrent output by the fifth balance detector is greater than a preset threshold value, outputting a control electric signal which is in direct proportion to the absolute value to act on the polarization scrambler, wherein the threshold value is 90% of the maximum photocurrent detected by the fifth balance detector.

13. The optical interconnect communication system of claim 8, wherein the originating DSP chip comprises:

the FEC encoding module is used for carrying out FEC encoding on the binary bit stream signal to be transmitted;

a constellation mapping module, configured to perform independent constellation mapping for X, Y two polarization states respectively according to a preset modulation format to generate two independent complex signal streams [ X₁，Y₁]^T；

A pre-coding module for applying the complex signal stream [ X₁，Y₁]^TPerforming polarization hierarchical precoding to output two precoded symbol streams [ X ]₂，Y₂]^TThe precoding rule is:

[X₂，Y₂]^T＝H·[X₁，Y₁]^T，

for the precoding matrix, it satisfies ad-bc ≠ 0.

The pre-compensation module is used for performing time domain pre-compensation on the two paths of signals after pre-coding after orthogonal separation;

and the DAC module is used for performing digital-to-analog conversion on the compensated signal by taking the baud rate as the sampling rate to obtain the analog electric signal.

14. The optical interconnect communication system of claim 13, wherein the receive DSP chip comprises:

an ADC module for converting the mixed electrical signal into a digital signal;

two low-pass filters for performing anti-aliasing filtering processing on the X-polarization signal and the Y-polarization signal respectively,

the two feedforward equalizers respectively correspond to one low-pass filter and carry out feedforward equalization on the filtered signals;

two clock recovery modules, which recover the best sampling clock and phase of each feedforward equalized signal;

the self-adaptive equalization module performs self-adaptive equalization on the signals after clock recovery to realize polarization demultiplexing to obtain two paths of equalized signals [ A ]₁，B₁]^T。

A de-precoding module using a matrix pair [ A ]₁，B₁]^TPerforming polarization-resolving diversity pre-coding processing to obtain [ A₂，B₂]^TThe rule of the polarization diversity precoding is as follows: [ A ]₂，B₂]^T＝H‘·[A₁，B₁]^TWherein H' is an inverse matrix of the precoding matrix H;

two constellation diagram mapping modules, which respectively de-map the signals after de-polarization diversity pre-coding;

and the two FEC decoding modules are used for respectively carrying out FEC decoding on the binary bit after demapping and recovering the binary bit stream signal.

15. The optical interconnect communication system of claim 14, wherein:

the precompensation module of the transmitting DSP chip adopts a real number domain finite impulse response filter to perform time domain precompensation, and the number of taps of the finite impulse response filter is less than or equal to 3;

the self-adaptive equalization module of the receiving end DSP chip adopts a single-tap 2x2 complex butterfly filter to carry out self-adaptive equalization;

the DAC module and the ADC module both work at a sampling rate of 1 baud rate.

Images