Dynamic polarization locker based on multi-step simulated annealing algorithm

Abstract

The invention discloses a dynamic polarization lock based on a multi-step simulated annealing algorithm, and belongs to the technical field of quantum communication and optical fiber communication. Aiming at the problem of polarization state drift caused by the influence of an external complex environment, the birefringence effect of an optical fiber, polarization mode dispersion and polarization dependent loss, energy of single pulse light is converted into peak voltage of output electric pulse in real time by utilizing an integral type optical signal detector based on a charge amplifier; and real-time measurement of the energy of a single optical pulse signal is realized. And a multi-step simulated annealing algorithm is rapidly operated by using the FPGA to search a target polarization state, so that high-speed polarization locking under the condition of pulsed light is realized. An extrusion type electric control polarization controller is utilized, piezoelectric ceramics are driven by applied voltage to extrude an optical fiber to change corresponding delay amount, and polarization state output of any target is controlled. The polarization state drift caused by the influence of an external complex environment, the birefringence effect of the optical fiber, polarization mode dispersion and polarization-dependent loss is effectively solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of quantum communication and optical fiber communication, and particularly relates to a dynamic polarization locker based on a multi-step analog annealing algorithm. BACKGROUND

[0002] A continuous variable quantum secure communication system adopts time division multiplexing and polarization multiplexing technology to transmit signal light fields and local oscillation light fields in the same long-distance single-mode optical fiber. During transmission, external factors such as temperature and humidity will cause birefringence of the single-mode optical fiber, resulting in changes in the polarization state in the single-mode optical fiber. The receiving end needs to use a dynamic polarization locker to restore and lock the polarization of the two light fields to a linear polarization state.

[0003] In an optical fiber communication system, the polarization state of an optical signal can be affected by various external factors such as temperature, humidity, and mechanical stress. These factors can cause birefringence in the optical fiber, which in turn causes changes in the polarization state of the optical signal. This random change in polarization state can cause signal attenuation, distortion, and an increase in bit error rate, severely affecting the performance and reliability of the communication system. A dynamic polarization locker can monitor and adjust the polarization state of an optical signal in real time, and is widely used in optical fiber communication systems to solve problems caused by changes in polarization state.

[0004] A polarization control algorithm can monitor changes in the polarization state in real time and restore and lock the polarization state to the desired polarization state by adjusting the parameters of the polarization controller, thereby ensuring stable transmission of the signal. Existing polarization control algorithms include gradient algorithms, genetic algorithms, and particle swarm optimization algorithms, which have obvious shortcomings: gradient algorithms are prone to local minimum values and are sensitive to initial values; genetic algorithms have high computational complexity and complex parameter settings; and particle swarm optimization algorithms are prone to local optimal solutions and are sensitive to parameter settings. Whether a polarization control algorithm is suitable determines the convergence speed, adaptability, and ability to find the optimal solution of the algorithm in a dynamic polarization locker. SUMMARY

[0005] To solve the problem of polarization state drift caused by the influence of complex external environments, the birefringence effect of the optical fiber, polarization mode dispersion, and polarization-dependent loss, the application uses an analog annealing algorithm as the basic algorithm, and in the inner loop of the algorithm, a multi-step updating method is proposed when updating the control voltage. The step size is combined with the extinction ratio of the input polarization state, and different input polarization states have different step size updating functions, which facilitates the algorithm to efficiently find the global optimal solution and quickly search for the target polarization state.

[0006] To solve the above technical problems, the application adopts the following technical solutions:

[0007] A dynamic polarization locker based on a multi-step simulated annealing algorithm includes a polarization beamsplitter. The optical signal is split into two paths by the polarization beamsplitter: one path is directly output, and the other enters an integrating optical signal detector. The energy of a single pulse of light is converted in real time into the peak voltage of the output electrical pulse, which is then input to a high-speed A / D converter. The voltage signal is converted into a digital signal and used as feedback to the extrusion-type electrically controlled polarization controller when loading the initial voltage value. This feedback is then input to an FPGA. The FPGA rapidly runs the multi-step simulated annealing algorithm to find the target polarization state. In each loop, the extruder voltage value is updated using a step function corresponding to the feedback signal voltage range and loaded into the extrusion-type electrically controlled polarization controller, driving the piezoelectric ceramic to extrude the optical fiber and change the corresponding delay. The integrating optical detector collects the feedback signal, and the polarization extinction ratio eventually stabilizes at a set threshold after multiple loops, achieving the output of the target polarization state.

[0008] Furthermore, the multi-step simulated annealing algorithm for finding the target polarization state specifically involves proposing a multi-step update method when updating the control voltage in the inner loop of the simulated annealing algorithm. This method divides the voltage signal collected by the integrating optical signal detector into several different voltage intervals, with each voltage interval corresponding to a different step voltage update function.

[0009] Furthermore, when the step function is a three-step update function, the voltage range is divided into... And the three ranges above 3.5V.

[0010] Furthermore, when the step function is a six-step update function, the voltage range is divided into... , , , , And six ranges above 4V.

[0011] Set the number of inner and outer loops in the simulated annealing algorithm to l and k, respectively, and the initial temperature to T0.

[0012] Set the initial value of the inner loop to i = 1; the initial value of the outer loop to n = 1; define the temperature update function as an exponentially decreasing function. ;

[0013] The fixed initial voltage values ​​(V1, V2, V3, V4) of the squeezer of the squeeze-type electrically controlled polarization controller are acquired and applied to the squeeze-type electrically controlled polarization controller. The peak value of the local optical field pulse V, which serves as the second feedback signal, is acquired. i A new set of voltage values ​​is obtained after calculation using the step voltage function. and the third feedback signal V t Simultaneously calculate the polarization extinction ratio under the current conditions;

[0014] Compare the increment Δ=V calculated after the second feedback signal t -V i If Δ < 0, accept a new set of voltage values. The current solution is given; if Δ > 0, the probability is calculated. , Given the current annealing temperature, set α to a random number between 0 and 1. If P ≥ α, accept a new set of voltage values ​​as the current solution; otherwise, continue with the original set of voltage values ​​as the current solution for the next calculation.

[0015] Update the inner loop count i = i + 1; if i < l, return to the previous step; if i > l, update the outer loop count. At the same time, update the current annealing temperature. ;

[0016] The algorithm monitors the current polarization extinction ratio in real time. If the set polarization extinction ratio threshold is met, the algorithm terminates, polarization locking is completed, and the current solution is the optimal solution. If the set polarization extinction ratio threshold is not met, the loop iteration ends when n>k, and the current solution is output as the optimal solution.

[0017] Furthermore, the electrical signal converted by the integrating optical signal detector is used to eliminate the influence of electronic noise by averaging the data from multiple points.

[0018] Furthermore, the FPGA-based fast multi-step simulated annealing algorithm is specifically implemented by using the FPGA digital port to drive a squeeze-type electrically controlled polarization controller, while simultaneously controlling a high-speed A / D converter to acquire feedback signals.

[0019] Furthermore, the polarization extinction ratio threshold is 30 dB.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The architecture of this invention adopts an "integrating optical signal detector + FPGA + squeeze-type electrically controlled polarization controller" pattern. An integrating optical signal detector is selected to convert the energy of a single pulse of light into the peak voltage of the output electrical pulse in real time. The voltage signal is processed by averaging data from multiple points to eliminate the influence of electronic noise. The FPGA has the advantages of fast hardware data processing speed and good real-time performance; selecting it as the hardware for the polarization control algorithm ensures efficient and accurate operation. The squeeze-type electrically controlled polarization controller is selected as the polarization controller, which can be perfectly driven by the FPGA to execute the polarization locking function, and also has advantages such as low insertion loss, low return loss, and fast response speed.

[0022] 2. This invention selects a multi-step simulated annealing algorithm as the polarization control algorithm. As a simulated annealing algorithm, it can effectively avoid local optima. By simulating the physical system's random exploration at high temperatures and gradual stabilization during gradual cooling, it finds the global optimum with a high probability. It is relatively insensitive to initial solutions and parameter selection, and has strong global search capabilities and adaptability. The multi-step simulated annealing algorithm combines the step size with the extinction ratio of the input polarization state. Different extinction ratios of different input polarization states correspond to different step size update functions, enabling the algorithm to find the global optimum more efficiently and quickly locate the target polarization state. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 The measurement results are for the multiple polarization state control of this invention;

[0026] Figure 3 The results of the polarization control time measurement according to the present invention;

[0027] Figure 4 This is a logical schematic diagram of the polarization control algorithm used in this invention. Detailed Implementation

[0028] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.

[0029] See Figure 1 , Figure 1 This is a schematic diagram of the structure of the present invention. The functions of each part are as follows:

[0030] Polarization beam splitter 1 splits the incident light field into two paths: one for direct output and the other for integrating optical signal detector 2. Integrating optical detector 2, based on a charge amplifier, converts the energy of a single pulse of light into the peak voltage of the output electrical pulse in real time. This voltage signal is used as a feedback signal input to high-speed A / D converter 3. High-speed A / D converter 3 acquires the feedback signal input from integrating optical detector 2, converts it into a digital signal, and inputs it to FPGA 4. FPGA 4 rapidly runs a multi-step analog annealing algorithm, updates the extruder voltage value using a step function corresponding to the feedback signal voltage range, and loads it into extrusion-type electrically controlled polarization controller 5. Based on the updated voltage value, extrusion-type electrically controlled polarization controller 5, driven by FPGA 4, extrudes the optical fiber with piezoelectric ceramics, changing the corresponding delay and thus altering the polarization state of the incident light.

[0031] in accordance with Figure 1 The steps for achieving polarization control in this product are as follows:

[0032] The optical signal is split into two paths by the polarization beam splitter 1. One path is directly output, and the other enters the integrating optical signal detector 2. The integrating optical detector 2, based on a charge amplifier, converts the energy of a single pulse of light into the peak voltage of the output electrical pulse in real time. This voltage signal is used as a feedback signal input to the high-speed A / D converter 3. The high-speed A / D converter 3 acquires the feedback signal input from the integrating optical detector 2, converts it into a digital signal, and inputs it into the FPGA 4. The FPGA 4 rapidly runs a multi-step analog annealing algorithm, updates the extruder voltage value according to the step function corresponding to the feedback signal voltage range, and loads it into the extrusion-type electrically controlled polarization controller 5. Based on the updated voltage value, the extrusion-type electrically controlled polarization controller 5, driven by the FPGA 4, extrudes the optical fiber with piezoelectric ceramics, changing the corresponding delay, thereby changing the polarization state of the incident light.

[0033] in accordance with Figure 1 The steps for achieving polarization control in this product are as follows:

[0034] The optical signal is split into two paths by the polarization beam splitter. One path is directly output, and the other path enters the integrating optical signal detector. The energy of a single pulse of light is converted into the peak voltage of the output electrical pulse in real time, and then input to a high-speed A / D converter. The voltage signal is converted into a digital signal, which is used as the feedback signal when the extrusion-type electrically controlled polarization controller loads the initial voltage value. The FPGA then quickly runs a multi-step analog annealing algorithm. In each loop, the extruder voltage value is updated by the step function corresponding to the feedback signal voltage range and loaded into the extrusion-type electrically controlled polarization controller. This drives the piezoelectric ceramic to extrude the optical fiber and change the corresponding delay. The integrating optical detector collects the feedback signal. After multiple loops, the polarization extinction ratio finally stabilizes at the set threshold, achieving the output of the target polarization state.

[0035] The extrusion-type electro-optic polarization controller used consists of 4 extruders. The angles between the 4 extruders and the x-axis direction are 0°, 45°, 0°, and 45° in sequence. The voltage range input to each channel of the extrusion-type electro-optic polarization controller is 0 - 5V, and the extrusion-type electro-optic polarization controller is driven by 20 digital output ports of the FPGA hardware.

[0036] This product uses FPGA4 to implement the multi-step simulated annealing algorithm to search for the target polarization state. Taking the polarization extinction ratio greater than 30dB as the decision threshold for the polarization control algorithm to stop, the specific implementation steps of the basic algorithm are as follows:

[0037] Set the number of inner loops and outer loops l and k in the simulated annealing algorithm, and the initial temperature T0; set the initial value of the inner loop i = 1; the initial value of the outer loop n = 1; define the temperature update function as an exponential decay function as ; Collect the fixed initial voltage values V1, V2, V3, V4 of the extruders of the extrusion-type electro-optic polarization controller, load them into the extrusion-type electro-optic

[0038] polarization controller, and collect the local optical field pulse peak value V i as the second feedback signal. After calculation by the step voltage function, a new set of voltage values and the third feedback signal V t are obtained, and the polarization extinction ratio in the current situation is calculated at the same time;

[0039] Compare the increment after calculation of the second feedback signal. If Δ < 0, accept the new set of voltage values as the current solution. If Δ > 0, calculate the probability , Ti is the current annealing temperature, set a as a random number from 0 to 1. If P ≥ a, accept the new set of voltage values as the current solution, otherwise continue to use the original

[0040] set of voltage values as the current solution for the next calculation;

[0041] Update the inner loop count i = i + 1; if i < l, return to execute the previous step; if i > l, update the outer loop count [[ID=3-- ;

[0042] Real-time monitor the current polarization extinction ratio. If the set polarization extinction ratio threshold is satisfied, terminate the algorithm operation, complete polarization locking, and the current solution is the optimal solution; if the set polarization extinction ratio threshold is not satisfied, when n > k, the loop iteration ends, and the current solution is output as the optimal solution.

[0043] The implementation steps of the multi-step simulated annealing algorithm are as follows: The voltage signal acquired by the integrating optical signal detector is divided into several different voltage intervals. When the step function is a three-step update function, the voltage intervals are divided into... And three intervals above 3.5V; when the step function is a six-step update function, the voltage interval is divided into three ranges. , , , , And six voltage ranges above 4V, with different step voltage update functions corresponding to different voltage ranges.

[0044] Figure 2 The measurement results of the multiple polarization state control of this invention are as follows. Figure 3 The polarization control time measurement results of this invention show that after polarization locking, the average time to complete polarization control is 803 μs, and the probability of polarization control being greater than 30 dB is 91%. Figure 4 This is a schematic diagram of the simulated annealing algorithm.

[0045] This invention discloses a dynamic polarization locker based on a multi-step simulated annealing algorithm. It utilizes an integrating optical signal detector based on a charge amplifier to convert the energy of a single pulse of light into the peak voltage of the output electrical pulse in real time, achieving real-time measurement of the energy of a single optical pulse signal. An FPGA is used to rapidly run the multi-step simulated annealing algorithm to search for the target polarization state, achieving high-speed polarization locking in pulsed light conditions. A squeeze-type electrically controlled polarization controller is used to drive a piezoelectric ceramic electrode through the applied voltage.

[0046] By altering the corresponding delay in ceramic-extruded optical fibers, the output polarization state of any target can be controlled. This invention effectively solves the polarization state drift caused by the influence of complex external environments, the birefringence effect of optical fibers, polarization mode dispersion, and polarization-dependent losses.

[0047] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A dynamic polarization locker based on a multi-step simulated annealing algorithm, characterized in that: The system includes a polarization beam splitter (1). The optical signal is split into two paths by the output optical field of the polarization beam splitter (1). One path is directly output, and the other path enters the integrating optical signal detector (2). The energy of a single pulse light is converted into the peak voltage of the output electrical pulse in real time, and then input into a high-speed A / D (3). The voltage signal is converted into a digital signal and used as the feedback signal when the initial voltage value is loaded into the extrusion type electrically controlled polarization controller (5). The FPGA (4) quickly runs a multi-step simulated annealing algorithm to find the target polarization state. In each cycle, the extruder voltage value is updated by the step function corresponding to the voltage range of the feedback signal and loaded into the extrusion type electrically controlled polarization controller (5). This drives the piezoelectric ceramic to extrude the optical fiber and change the corresponding delay. The integrating optical detector (2) collects the feedback signal. The polarization extinction ratio is finally stabilized at the set threshold after multiple cycles, realizing the output of the target polarization state.

2. The dynamic polarization locker based on a multi-step simulated annealing algorithm according to claim 1, characterized in that: The multi-step simulated annealing algorithm for finding the target polarization state is as follows: when updating the control voltage in the inner loop of the simulated annealing algorithm, a multi-step update method is proposed, and the voltage signal collected by the integrating optical signal detector (2) is divided into several different voltage intervals, and different voltage intervals correspond to different step voltage update functions. Set the number of inner and outer loops in the simulated annealing algorithm to l and k, respectively, and the initial temperature to T0. Set the initial value of the inner loop to i = 1; and the initial value of the outer loop to n = 1. Define the temperature update function as an exponentially decreasing function. ; The fixed initial voltage values ​​V1, V2, V3, and V4 of the extruder of the extrusion type electrically controlled polarization controller (5) are collected and applied to the extrusion type electrically controlled polarization controller (5). The peak value of the local optical field pulse V, which serves as the second feedback signal, is collected. i A new set of voltage values ​​is obtained after calculation using the step voltage function. and the third feedback signal V t Simultaneously calculate the polarization extinction ratio under the current conditions; Compare the increment Δ=V calculated after the second feedback signal t -V i If Δ < 0, accept a new set of voltage values. The current solution is given; if Δ > 0, the probability is calculated. , Given the current annealing temperature, set α to a random number between 0 and 1. If P ≥ α, accept a new set of voltage values ​​as the current solution; otherwise, continue with the original set of voltage values ​​as the current solution for the next calculation. Update the inner loop count i = i + 1; if i < l, return to the previous step; if i > l, update the outer loop count. At the same time, update the current annealing temperature. ; The algorithm monitors the current polarization extinction ratio in real time. If the set polarization extinction ratio threshold is met, the algorithm terminates, polarization locking is completed, and the current solution is the optimal solution. If the set polarization extinction ratio threshold is not met, the loop iteration ends when n>k, and the current solution is output as the optimal solution.

3. A dynamic polarization locker based on a multi-step simulated annealing algorithm according to claim 1, characterized in that: The electrical signal converted by the integrating optical signal detector (2) is used to eliminate the influence of electronic noise by averaging the data from multiple points.

4. A dynamic polarization locker based on a multi-step simulated annealing algorithm according to claim 1, characterized in that: The FPGA (4) fast-running multi-step simulated annealing algorithm is specifically achieved by using the FPGA (4) digital port to drive the extrusion type electrically controlled polarization controller (5) and simultaneously control the high-speed A / D (3) to collect feedback signals.

5. A dynamic polarization locker based on a multi-step simulated annealing algorithm according to claim 1, characterized in that: The polarization extinction ratio threshold is 30dB.

6. A dynamic polarization locker based on a multi-step simulated annealing algorithm according to claim 2, characterized in that: When the step function is a three-step update function, the voltage range is divided into... And the three ranges above 3.5V.

7. A dynamic polarization locker based on a multi-step simulated annealing algorithm according to claim 2, characterized in that: When the step function is a six-step update function, the voltage range is divided into... , , , , And six ranges above 4V.

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