Apparatus and method for implementing pon rate adjustment based on polar modulation

Abstract

The application provides a device and a method for realizing PON rate adjustment based on Polar modulation, and relates to the technical field of passive optical networks.The device comprises a first external cavity laser, a second external cavity laser, a dual-polarization phase quadrature modulator, an arbitrary waveform generator, an erbium-doped fiber amplifier, a single-mode optical fiber, a variable optical attenuator, a coherent receiver and an oscilloscope.The method comprises the following steps: dynamically adjusting the number of information bits A, splicing check bits to form total information bits, optimizing the distribution of information bits and frozen bits according to the optical signal channel sorting result, performing polar encoding on the signal at the encoding end, and mapping the signal into a 16QAM code symbol sequence by using the Polar modulation technology; at the receiving end, calculating the LLR, calculating the path metric value of all paths and performing a pruning operation when the list width reaches a set value, and detecting the L candidate paths by using the CRC check after the decoding is completed.The application realizes flexible regulation and control of the transmission rate of different optical network units.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of passive optical network, and in particular to a device and method for realizing PON rate adjustment based on Polar modulation. BACKGROUND

[0002] With the rapid development of services such as Internet of Things, high-definition streaming media and mixed reality, passive optical network (PON) plays a vital role in providing last mile connectivity to end users. With the standardization of 50G PON, the peak rate of the next generation PON can reach 200 Gb / s, which can require coherent optical technology and advanced digital signal processing (DSP) algorithms to maintain high power budget requirements. In the current PON structure, all optical network units (ONUs) receive the same downstream signal from an optical line terminal (OLT). The peak rate is limited by the worst-case power budget, which is mainly related to the maximum supported optical path loss (OPL). In the existing optical distribution network (ODN), it is difficult to transmit the same downstream signal at such a high data transmission rate to edge ONUs with large OPL. At the same time, the same data transmission rate between ONUs in the downstream link can also cause waste of spectrum resources of ONUs with small OPL and good channel conditions.

[0003] Several methods have been proposed to adjust the information rate between ONUs, among which the most direct method is based on adaptive coding and modulation (ACM). The ACM method uses two-level, three-level and four-level pulse amplitude modulation (PAM) with fixed symbol rate, and low-density parity-check code (LDPC) derived from the mother code through shortening and puncturing. In order to further expand the adjustment range of data rate, subcarrier multiplexing technology is used for both upstream and downstream signals in the coherent PON scheme. Since the coherent receiver has fixed frequency selectivity, the ONU can select the required subcarriers for detection. The subcarrier multiplexing scheme also helps to extract the carrier phase information, thereby reducing the requirement for laser linewidth and the cost of the ONU-end laser. Probability shaping (PS) and geometric shaping (GS) optimize the modulation format through different mechanisms to adjust the signal information rate and improve channel utilization. However, the above schemes can require the addition of a digital signal processor (DSP) or a long code block decoder at the ONU end, increasing the computational complexity or the cost of each end user. SUMMARY

[0004] The present application aims to solve the problem of information rate adjustment of PON system under different transmission conditions, and proposes a device for realizing PON rate adjustment based on Polar modulation, comprising: a first external cavity laser, a second external cavity laser, a dual-polarization phase quadrature modulator, an arbitrary waveform generator, an erbium-doped fiber amplifier, a single-mode optical fiber, a variable optical attenuator, a coherent receiver and an oscilloscope.

[0005] The first external cavity laser serves as a light source, and inputs a light signal to a light input port of a dual-polarization quadrature phase modulation device; an arbitrary waveform generator loads a 16QAM code symbol sequence generated offline in advance, and an analog electrical signal generated by the arbitrary waveform generator is modulated into an optical signal by the dual-polarization quadrature phase modulation device, the modulated optical signal is amplified by an erbium-doped fiber amplifier, and then transmitted to a variable optical attenuator by a single-mode optical fiber for adjustment, the adjusted optical signal and an optical signal output by a second external cavity laser are input into a coherent receiver, a signal output by the coherent receiver is sampled by an oscilloscope, and a transmission signal is recovered by offline signal processing.

[0006] Further, the arbitrary waveform generator is a four-channel arbitrary waveform generator.

[0007] Further, the first external cavity laser has a wavelength of 1550 nm and a line width of 100 kHz.

[0008] Further, the dual-polarization quadrature phase modulation device is internally integrated with four drivers.

[0009] The application further provides a method for realizing PON rate adjustment based on Polar modulation, and the method is realized based on the above device and comprises the following steps:

[0010] The received optical signal channel is evaluated, and each polarization channel is sorted;

[0011] The number of signal bits A is dynamically adjusted, the total information bits are formed by splicing the check bits, and the distribution of the information bits and the frozen bits is optimized according to the sorting result;

[0012] The generation matrix is The input information is polarization encoded, wherein is an inverse permutation matrix, F is a basic kernel matrix, and N is the code length; the obtained polarization code word is processed by adaptation, and then mapped into a 16QAM code symbol sequence by using a Polar modulation technology; and the arbitrary waveform generator loads the 16QAM code symbol sequence.

[0013] The output signal of the device is subjected to signal recovery by offline signal processing, and the decoding process of the offline signal processing comprises the following steps: calculating the log-likelihood ratio (LLR) of each transmission bit, in successive cancellation list decoding, for each unfrozen bit, two different result expansion paths of 0 and 1 need to be considered, when the list width L reaches a set value, the path metric values (PM) of all paths are calculated and sorted, and a pruning operation is performed, after decoding is completed, the L candidate paths are detected by using CRC check, and a decoded signal is obtained.

[0014] Further,

[0015] The polar channels are sorted by using the Bachman parameter, and the smaller the Bachman parameter is, the more reliable the channel is.

[0016] Further, the LLR is defined as:

[0017] ,

[0018] wherein, represents the log-likelihood ratio of represents the i-th bit of the signal, represents the probability that the i-th bit of the signal is 0, represents the probability that the i-th bit of the signal is 1, and y represents the signal.

[0019] The application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the method for realizing PON rate adjustment based on Polar modulation.

[0020] The application further provides an electronic device, which comprises a processor and a memory, the processor and the memory are connected with each other, the memory is used for storing a computer program, the computer program comprises computer readable instructions, the processor is configured to call the computer readable instructions to execute the method for realizing PON rate adjustment based on Polar modulation.

[0021] The application further provides a computer program product, which comprises computer program / instructions, and the computer program / instructions are executed by a processor to realize the steps of the method for realizing PON rate adjustment based on Polar modulation.

[0022] The application provides the technical scheme, and the beneficial effects are as follows:

[0023] The application realizes channel reliability sorting by using the polarization principle, and can realize flexible regulation and control on transmission rates of different optical network units (ONUs) under the premise of ensuring equivalent or better performance by means of the CRC-aided successive cancellation list (CRC-SCL) decoding algorithm. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a device structure diagram for realizing PON rate adjustment based on Polar modulation in the embodiment of the application;

[0025] Figure 2 is a BER comparison diagram of two decoding algorithms CRC-SCL and SC of Polar when the code rate is in the embodiment of the application;

[0026] Figure 3 is a BER comparison diagram of two decoding algorithms CRC-SCL and SC of Polar when the code rate is A comparison of the BER of Polar's two decoding algorithms, CRC-SCL and SC;

[0027] Figure 4 This is a block diagram of an electronic device according to an exemplary embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0029] The structural diagram of the device for PON rate regulation based on Polar modulation in this embodiment of the invention is shown below. Figure 1 Specifically, it includes:

[0030] First external cavity laser, second external cavity laser, dual polarization phase orthogonal modulator, arbitrary waveform generator, erbium-doped fiber amplifier, single-mode fiber, variable optical attenuator, coherent receiver, oscilloscope.

[0031] In this embodiment of the invention, the first external cavity laser operates at a wavelength of 1550 nm and has a linewidth of approximately 100 kHz. The arbitrary waveform generator is a four-channel unit, and the dual-polarization phase quadrature modulator integrates four drivers to achieve independent modulation of the dual-polarization signal. Four different code rate configurations are preset, with information bit rates of 100 Gb / s, 133.33 Gb / s, 150 Gb / s, and 166.67 Gb / s, respectively. Furthermore, the device can dynamically adjust the preset rate range based on the actual measured signal-to-noise ratio and other transmission conditions of the channel, thereby achieving optimal data transmission efficiency while ensuring transmission performance.

[0032] The device operates as follows: A first external cavity laser acts as the light source, inputting an optical signal into the optical input port of a dual-polarization phase quadrature modulator. An arbitrary waveform generator loads a pre-generated offline 16QAM coded symbol sequence, with the baud rate of the 16QAM signal set to 25 Gbaud, thus achieving a maximum raw data rate of 200 Gb / s across the two polarization components. The analog electrical signal generated by the arbitrary waveform generator is modulated into an optical signal by the dual-polarization phase quadrature modulator. The modulated optical signal is amplified by an erbium-doped fiber amplifier and then transmitted through a standard single-mode fiber (over 48 km) to a variable optical attenuator for fine adjustment (in 0.3 dB steps) to obtain appropriate optical power at the receiving end. The adjusted optical signal and the optical signal output from the second external cavity laser are input to a coherent receiver. The second external cavity laser acts as a local oscillator. The signal output from the coherent receiver is sampled at high speed using an oscilloscope, and the transmitted signal is recovered through offline signal processing. The performance of the device is then evaluated.

[0033] Traditional applications of Flexible Forward Error Correction (FEC) coding to Flexible Rate PON combine different modulation techniques with Low-Density Parity-Check (LDPC) codes. LDPC codes shorten S bits and puncture P bits, resulting in a fixed codeword length of 115200 bits (information K + parity M). Net rate flexibility can be achieved by calculating K / (K+M). However, this flexible FEC coding approach sacrifices coding gain; furthermore, the wider the rate adjustment range, the greater the total number of shortened and punctured bits, leading to a greater loss of coding gain. As a novel FEC coding method, Polar codes have been adopted by 5G radios as channel coding for control information. This invention achieves flexible PON rate adjustment based on Polar modulation technology. For a Polar code to meet certain requirements... That is, N must be an integer power of 2; K is the number of signal bits A plus the number of parity bits, and N represents the code length. By adjusting the number of signal bits A, the code rate can be varied from 0 to 1. This flexible adjustment method avoids the operation of reducing or increasing the codeword length, thus reducing the loss of coding gain to a certain extent. The coding gain of Polar codes mainly depends on the effect of channel polarization. Lower code rates usually select more high-quality channels, thereby improving coding gain; while higher code rates may use some lower-quality channels, resulting in a decrease in coding gain. The present invention provides a method for PON rate adjustment based on Polar modulation implemented by the above-mentioned device, comprising:

[0034] The received optical signal channels are evaluated, and the various polarization channels are ranked. In Polar coding, the Bachmann parameter or other channel reliability metrics are used to evaluate the received optical signal channels; the smaller the Bachmann parameter, the more reliable the channel.

[0035] The number of signal bits A is dynamically adjusted. After splicing the check bits to form the total information bits, the distribution of information bits and frozen bits is optimized according to the sorting results. As much high-quality channel as possible is used to transmit information bits, thereby improving system reliability and enabling flexible rate changes.

[0036] A generator matrix is ​​used at the encoding end. The input information is polar-coded, where F is the inverted permutation matrix, F is the basic kernel matrix, and N is the code length. After the obtained polar codewords are adapted, they are mapped to 16QAM coded symbol sequences or other high-order modulation format signals using Polar modulation technology, so as to achieve flexible adjustment of the information rate preset value (such as 100Gb / s, 133.33Gb / s, 150Gb / s, 166.67Gb / s, etc.).

[0037] An arbitrary waveform generator loads a 16QAM encoded symbol sequence. The first external cavity laser serves as the light source, inputting the optical signal into the optical input port of a dual-polarization phase quadrature modulator. The analog electrical signal generated by the arbitrary waveform generator is modulated into an optical signal by the dual-polarization phase quadrature modulator. The modulated optical signal is amplified by an erbium-doped fiber amplifier and then transmitted through a single-mode fiber to a variable optical attenuator for adjustment. The adjusted optical signal and the optical signal output from the second external cavity laser are input into a coherent receiver. The signal output from the coherent receiver is sampled by an oscilloscope, and the transmitted signal is recovered through offline signal processing.

[0038] Offline signal processing specifically includes: performing dispersion compensation, down-conversion, synchronization, and frequency estimation on the signal; using constant modulus algorithm (CMA) and decision-oriented minimum mean square error algorithm (DDLMS) for adaptive filtering; then performing quadrature amplitude modulation demapping; and finally performing forward error correction decoding.

[0039] The decoding process is as follows: At the receiving end, the log-likelihood ratio (LLR) for each transmitted bit is calculated. This LLR is used for subsequent updates and iterations of the signal's soft information and provides crucial information for soft-decision-based detection, thereby improving overall decision accuracy. The LLR is defined as: ,in, express The log-likelihood ratio, This represents the i-th bit of the signal. This represents the probability that the i-th bit of the signal is 0. Let y represent the probability that the i-th bit of the signal is 1. In continuous cancellation list decoding, for each unfrozen bit, two different results (0 and 1) need to be considered to expand the path. When the list width L reaches a set value, the path metric PM of all paths is calculated and sorted, and a pruning operation is performed to retain the most probable path while keeping complexity and delay controllable. After decoding, CRC checksum is used to check the L candidate paths. This mechanism allows SCL decoding to rely not only on path metrics but also on the verification of overall codeword consistency, thereby achieving approximate maximum likelihood (ML) decoding performance and significantly improving overall decoding accuracy and system stability.

[0040] Based on preset adjustment strategies and real-time feedback data, the encoding, mapping, and transmission parameters during Polar modulation can be dynamically adjusted without requiring significant modifications to the decoding end. This design not only simplifies hardware implementation but also significantly expands the system's applicability and compatibility. Through closed-loop control, the downlink signal can be matched to the optimal rate according to the actual channel conditions of the ONU, thereby enabling flexible information rate switching of the entire PON system under different transmission conditions.

[0041] This invention uses simulation and experiments to compare and analyze the BLER and BER of the Polar CRC-SCL algorithm with total code lengths of approximately 500 and 1000, as well as two LDPC decoding algorithms, at four preset code rates. The results show that the Polar decoder, employing cyclic redundancy check and a continuous cancellation list algorithm, exhibits superior or near-optimal receiver sensitivity at short block lengths and various code rates compared to the LDPC decoder.

[0042] Figure 2 and Figure 3 The bitrates were shown as follows and The BER performance of Polar CRC-SCL and Polar SC with different list widths is compared. SC can be considered a SCL algorithm with a list width of 1, requiring no path sorting or pruning, and decoding bit-by-bit along a single path. Therefore, path selection or intermediate bit decoding errors significantly impact decoding performance. SCL, by introducing a wider list, achieves a significant performance improvement. Specifically, Figure 2 When the code rate is At that time, SCL with a list width of 8 is larger than SC. The received optical power was increased by approximately 1.65 dB. Figure 3 In the middle, when the code rate is At that time, the received optical power increased by approximately 1.08 dB. Combined with... Figure 2 and Figure 3 The test results in the middle, when using When the code rate is combined with a CRC-SCL decoder (list width nL=8), the received optical power is the lowest (decoding performance is the best); in contrast, when a higher code rate is used with an SC decoder, the received optical power is higher, and the performance difference between the two is about 6.45 dB.

[0043] Therefore, when channel conditions are poor (e.g., a harsh environment at the ONU end), the allocatable code rate is... Furthermore, Polar CRC-SCL has a wider list width; and when channel conditions are favorable (good ONU environment), the allocable code rate is [missing information]. Even higher Polar SC or Polar CRC-SCL with a smaller list width. In summary, this invention can flexibly achieve dynamic adjustment of the passive optical network (PON) rate and improve spectrum resource utilization by adjusting the Polar decoding algorithm and the selection of the number of information bits A, providing a wider range of configuration combinations and code rate adjustment, demonstrating significant technical advantages.

[0044] In one exemplary embodiment, a computer-readable storage medium is included, which stores a computer program that, when executed by a processor, implements the above-described method for PON rate regulation based on Polar modulation.

[0045] Please see Figure 4 In one exemplary embodiment, the device further includes an electronic device including at least one processor, at least one memory, and at least one communication bus.

[0046] The memory stores a computer program, which includes computer-readable instructions. The processor calls the computer-readable instructions stored in the memory through the communication bus to execute the above-mentioned method for PON rate regulation based on Polar modulation.

[0047] In one exemplary embodiment, a computer program product is proposed, including a computer program / instructions that, when executed by a processor, implement the steps of the above-described method for PON rate regulation based on Polar modulation.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for PON rate regulation based on Polar modulation, characterized in that, The device comprises: a first external cavity laser, a second external cavity laser, a dual polarization phase quadrature modulator, an arbitrary waveform generator, an erbium-doped fiber amplifier, a single-mode fiber, a variable optical attenuator, a coherent receiver, and an oscilloscope. The first external cavity laser serves as a light source and inputs an optical signal to an optical input port of the dual polarization phase quadrature modulator; the arbitrary waveform generator loads a 16QAM code symbol sequence generated offline in advance, an analog electrical signal generated by the arbitrary waveform generator is modulated into an optical signal by the dual polarization phase quadrature modulator, the modulated optical signal is amplified by the erbium-doped fiber amplifier, and then transmitted to the variable optical attenuator by the single-mode fiber for adjustment, the adjusted optical signal and an optical signal output by the second external cavity laser are input to the coherent receiver, a signal output by the coherent receiver is sampled by the oscilloscope, and a transmission signal is recovered through offline signal processing. The generation of the 16QAM code symbol sequence comprises: evaluating a received optical signal channel and sorting each polarization channel; optimizing the distribution of information bits and frozen bits according to the sorting result after dynamically adjusting the number of signal bits A and splicing check bits to form total information bits; Adopting a generator matrix The input information is polar encoded, wherein is an inverse permutation matrix, F is a base kernel matrix, and N is a code length; the obtained polar code word is mapped into a 16QAM code symbol sequence after an adaptation process and using a Polar modulation technique. 2.The device for implementing PON rate adjustment based on Polar modulation according to claim 1, wherein, The arbitrary waveform generator is a four-channel arbitrary waveform generator. 3.The device for implementing PON rate adjustment based on Polar modulation of claim 1, wherein, The wavelength of the first external cavity laser is 1550 nm, and the line width is 100 kHz.

4. The device for implementing PON rate adjustment based on Polar modulation according to claim 1, characterized in that, The dual polarization phase quadrature modulator is internally integrated with four drivers.

5. A method for implementing PON rate adjustment based on Polar modulation, characterized in that, The device is implemented based on any one of claims 1-4, comprising: The arbitrary waveform generator loads a 16QAM code symbol sequence. The output signal of the device is subjected to offline signal processing for signal recovery, wherein the decoding process of the offline signal processing comprises: calculating the log-likelihood ratio (LLR) of each transmission bit, in successive cancellation list decoding, considering two different result expansion paths (0 and 1) for each unfrozen bit, when the list width L reaches a set value, calculating and sorting the path metric (PM) values of all paths and performing a pruning operation, and after decoding, using CRC check detection for L candidate paths to obtain a decoded signal.

6. The method of claim 5, wherein Bachman parameters are used to sort each polarization channel, and the smaller the Bachman parameter, the more reliable the channel.

7. The method of claim 5, wherein the method comprises: The LLR is defined as: ， wherein denotes the log-likelihood ratio of denotes the i-th bit of the signal, denotes the probability that the i-th bit of the signal is 0, denotes the probability that the i-th bit of the signal is 1, y denotes the signal.

8. A computer readable storage medium storing a computer program, characterized in that: The computer program is executed by a processor to implement the method of any one of claims 5-7.

9. An electronic device, comprising: The computer program is executed by a processor to implement the method of any one of claims 5-7.

10. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instructions are executed by a processor to implement the steps of the method of any one of claims 5-7.

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