Polarization tracking method, device and storage medium

Abstract

The present invention belongs to the field of polarization multiplexing technology and discloses a polarization tracking method, device and storage medium, including: at the communication receiving end, calculating the current polarization rotation state speed Δφ based on the received optical signal; flexibly configuring the pilot interval ΔL currently required by the MIMO equalizer according to Δφ; Rx ; Then, determine ΔL Rx The starting point in the received signal frame is used to achieve frame synchronization; after frame synchronization, the MIMO equalizer starts from the starting point and the interval ΔL Rx The method obtains pilot signals from the signal frame to calculate update coefficients for the MIMO equalizer, and then performs butterfly filtering on the received signal to achieve polarization tracking. It also includes comparing Δφ with a threshold and, based on the comparison result, selecting either an automatic polarization controller or a MIMO equalizer for polarization tracking. The present invention allows for flexible configuration of pilot signal spacing and polarization rotation processing methods, enabling high-dynamic range polarization tracking while reducing power consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of polarization multiplexing, and more specifically, relates to a polarization tracking method, device and storage medium. Background Art

[0002] With the development of high-speed fiber-optic transmission technology, polarization multiplexing (PDM) is required to double spectral efficiency. PDM allows different optical signals to be modulated onto two orthogonal polarization states at the same wavelength, thereby doubling the transmission rate while occupying the same wavelength band. However, due to polarization effects in optical fiber links, the polarization states of optical signals undergo random rotations during transmission. This can cause mutual interference and aliasing between the two PDM branches, leading to incorrect demultiplexing. PDM tracking can resolve aliasing between the two PDM branches and achieve correct demultiplexing.

[0003] Currently, the commonly used polarization tracking solution is based on the MIMO (Multiple-Input Multiple-Output) equalizer in electrical domain digital signal processing for deflection tracking. However, since the MIMO equalizer converges through a butterfly filter, the computational complexity is high, resulting in high power consumption.

[0004] An automatic polarization controller can also control and adjust the polarization state of the optical signal in real time. It can monitor and adjust the polarization state of the incident light to ensure that the signal always maintains the desired polarization state. An automatic polarization controller usually consists of a polarization controller and a feedback control system. It monitors and analyzes the polarization characteristics of the optical signal in real time, and adjusts it according to preset parameters and algorithms to achieve accurate control of the optical signal and avoid aliasing between the two polarization multiplexing branches. During operation, only the optical power at a specific polarization state needs to be used as feedback, and polarization tracking is achieved by minimizing (maximizing) the optical power at that polarization state. However, the polarization tracking speed of the automatic polarization controller is limited by the response speed of the device itself or the response speed of the external control circuit. Summary of the Invention

[0005] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a polarization tracking method, device and storage medium, which aim to reduce the power consumption required for polarization tracking of a MIMO equalizer.

[0006] To achieve the above object, according to a first aspect of the present invention, a polarization tracking method is provided, including a MIMO equalizer. The polarization tracking method includes:

[0007] At the communication receiving end, the current polarization rotation state velocity Δφ is calculated based on the received optical signal;

[0008] Calculate the pilot interval ΔL currently required by the MIMO equalizer according to the polarization rotation state speed Δφ Rx ; Among them, Δφ and ΔL Rx Inversely proportional relationship;

[0009] Determine the currently required pilot interval ΔL Rx The starting point in the received signal frame is used to achieve frame synchronization; wherein the received signal is an electrical signal after the received optical signal is photoelectrically converted and analog-to-digital converted;

[0010] After frame synchronization, the MIMO equalizer starts from the starting point and the interval ΔL Rx A pilot signal in the signal frame is obtained to calculate the update coefficient of the MIMO equalizer, and then butterfly filtering is performed on the received signal to achieve polarization tracking.

[0011] Furthermore, Δφ and ΔL Rx Satisfy between:

[0012] ΔL Rx =ceil(ΔL Tx *φ max / Δφ)

[0013] Among them, ceil represents a positive integer greater than or equal to, ΔL Tx represents the pilot interval inserted into the optical signal at the communication transmitter, φ max Indicates that the pilot interval is ΔL Tx The maximum polarization tracking speed supported by the pilot. * indicates a multiplication operation.

[0014] Furthermore, the currently required pilot interval ΔL is determined Rx The starting point in the received signal frame to achieve frame synchronization, including:

[0015] ΔL in the received signal frame Rx Slide within the symbol length to take the 1st to ΔLth Tx symbols as the starting point, with ΔL Tx Take N groups of pilots for the interval;

[0016] Perform cross-correlation calculations on the N groups of pilots and the pilot sequence inserted into the optical signal at the communication transmitting end, and take the symbol corresponding to the maximum cross-correlation value as the currently required pilot interval ΔL Rx The starting point in the received signal frame to achieve frame synchronization; where N = ΔL Rx / ΔL Tx .

[0017] Furthermore, the polarization rotation state velocity Δφ is greater than a preset threshold φ Thresh ;

[0018] And when Δφ≤φ Thresh When the polarization is detected, an automatic polarization controller is used for polarization tracking.

[0019] Furthermore, the calculation formula of the polarization rotation state velocity Δφ is:

[0020]

[0021] Wherein, V1 and V2 are the voltages corresponding to the two polarization states of the optical signal obtained by polarization splitting of the received optical signal converted into electrical signals; Δt represents the sampling period for sensing the current polarization rotation state speed; express The change between the initial and final moments of a sampling period.

[0022] According to a second aspect of the present invention, a polarization tracking device based on a MIMO equalizer is provided, comprising a MIMO equalizer, configured to perform the polarization tracking method according to any one of the first aspects, including:

[0023] a polarization rotation state speed calculation unit, configured to calculate, at a communication receiving end, a current polarization rotation state speed Δφ based on a received optical signal;

[0024] A dynamic pilot interval calculation unit is used to calculate the pilot interval ΔL currently required by the MIMO equalizer according to the polarization rotation state speed Δφ Rx ; Among them, Δφ and ΔL Rx Inversely proportional relationship;

[0025] Frame synchronization unit, used to determine the currently required pilot interval ΔL Rx At the starting point in the received signal frame, to achieve frame synchronization; wherein the received signal is an electrical signal obtained by photoelectric conversion of the received optical signal;

[0026] After frame synchronization, the MIMO equalizer starts from the starting point and the interval ΔL Rx A pilot signal in the signal frame is obtained to calculate the update coefficient of the MIMO equalizer, and then butterfly filtering is performed on the received signal to achieve polarization tracking.

[0027] Furthermore, the polarization rotation state velocity Δφ is greater than a preset threshold φ Thresh ;

[0028] And when Δφ≤φ Thresh When the polarization tracking device is used, it also includes an automatic polarization controller for polarization tracking.

[0029] Further, a coupler is included;

[0030] The coupler is used to split the received optical signal into two parts, one part of the light is used to input into the polarization rotation state speed calculation unit to calculate the current polarization rotation state speed Δφ; the other part of the light is used to calculate the current polarization rotation state speed Δφ when Δφ≤φ Thresh , input to the automatic polarization controller, when Δφ h > ser φ hT , it is input to the MIMO equalizer for polarization tracking.

[0031] Furthermore, it also includes a communication optical signal generating unit, which is used to modulate the communication signal onto a single-frequency optical carrier at the communication transmitting end to obtain an optical signal, and send it to the communication receiving end through an optical fiber link.

[0032] According to a third aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the polarization tracking method as described in any one of the first aspects is implemented.

[0033] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0034] (1) The present invention takes into account that in the prior art, when the MIMO equalizer performs polarization tracking, it uses a pilot signal with a fixed interval that is consistent with the pilot signal inserted by the transmitter to update the coefficients. When the current polarization rotation state speed is not so high, it will bring about greater power consumption. Therefore, the present invention dynamically configures the pilot signal interval required for tracking the polarization state change based on the currently perceived polarization rotation state speed Δφ. Specifically, the current polarization rotation state speed Δφ is configured to be inversely proportional to the required pilot signal interval. In this way, when the current polarization rotation state speed Δφ is relatively not so high, more pilot signal interval symbols can be configured (i.e., the pilot signal interval is longer). When the pilot signal obtained under this pilot signal interval is used to update the coefficients of the MIMO equalizer, the update speed of the MIMO equalizer can be reduced, thereby reducing the computational complexity of the MIMO equalizer and reducing the power consumption of the entire polarization tracking process.

[0035] (2) Furthermore, the present invention designs a specific relationship between the current polarization rotation state speed Δφ and the currently required pilot interval ΔL Rx Through experiments, it is found that when the pilot interval determined based on the designed relationship is used to update the coefficients of the MIMO equalizer, fast polarization tracking can be achieved and the required power consumption can be reduced.

[0036] (3) Furthermore, by sensing the current polarization rotation state speed Δφ, a judgment is made. When the current polarization rotation state speed Δφ is low, an automatic polarization controller is used for polarization tracking. The automatic polarization controller has a low algorithm complexity and is easy to implement low-power polarization tracking. When the current polarization rotation state speed Δφ is high, a MIMO equalizer is used for polarization tracking to achieve fast polarization tracking. In this way, a flexible configuration of polarization rotation processing with a high dynamic range is achieved, and there is no need to use a more complex MIMO equalizer even at low speeds, which further reduces the power consumption of the entire polarization tracking process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the polarization tracking method in an embodiment of the present invention.

[0038] Figure 2 This is a frame structure for rapid polarization change based on pilot in an embodiment of the present invention.

[0039] Figure 3 Schematic diagram of a polarization tracking method in an embodiment of the present invention.

[0040] Figure 4 Schematic diagram of a polarization tracking device in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0042] Example 1

[0043] like Figure 1 As shown, an embodiment of the present invention provides a polarization tracking method, which mainly includes:

[0044] At the communication receiving end, the current polarization rotation state velocity Δφ is calculated based on the received optical signal;

[0045] Calculate the pilot interval ΔL currently required by the MIMO equalizer based on the current polarization rotation state speed Δφ Rx , which is the number of pilot interval symbols; where the current polarization rotation state speed Δφ is equal to the current required pilot interval ΔL Rx Inversely proportional relationship; In the embodiment of the present invention, Δφ and ΔL are designed Rx Satisfy between: ΔL Rx =ceil(ΔL Tx *φ max / Δφ); where ceil represents a positive integer greater than or equal to ΔL Tx Indicates the pilot interval inserted by the communication transmitter, φ max The interval is ΔL Tx The maximum polarization tracking speed that the pilot can support; In the embodiment of the present invention, it can be found through experiments that based on Δφ, ΔL Rx and φ max The designed relationship can achieve fast polarization tracking and reduce the required power consumption.

[0046] Determine the currently required pilot interval ΔL Rx The starting point in the received signal frame is used to achieve frame synchronization; wherein the received signal is an electrical signal after the optical signal at the receiving end is processed by photoelectric conversion and analog-to-digital conversion.

[0047] After frame synchronization, the MIMO equalizer starts from ΔL Rx Starting from the starting point, the interval length ΔL Rx The pilot signal is obtained to calculate the update coefficients of the MIMO equalizer, which is then butterfly filtered with the received signal to achieve polarization tracking.

[0048] In the embodiment of the present invention, the frame structure of the communication signal is as follows: Figure 2 As shown, where ΔL Rx It is the currently required pilot interval determined according to the current polarization rotation state speed Δφ in the present invention.

[0049] Specifically, determine the currently required pilot interval ΔL Rx The starting point in the received signal frame to achieve frame synchronization, including:

[0050] ΔL in the current signal frame Rx Slide within the symbol length to take the 1st to ΔLth Tx symbols as the starting point, with ΔL Tx Take N groups of pilot symbols at intervals and perform cross-correlation calculations with the pilot sequence of the transmitting end respectively. The symbol corresponding to the maximum cross-correlation value is taken as the starting point in the received signal frame to achieve frame synchronization, where N = ΔL Rx / ΔL Tx .

[0051] When using a MIMO equalizer for polarization tracking, compared with the method in the prior art in which the MIMO equalizer uses a pilot signal that is consistent with and fixed in interval inserted into the transmitting end signal for polarization tracking, the present invention dynamically configures the pilot interval required for tracking polarization state changes based on the currently perceived polarization rotation state speed Δφ. Specifically, the current polarization rotation state speed Δφ is configured to be inversely proportional to the required pilot interval. When the current polarization rotation state speed Δφ is relatively not so high, more pilot interval symbols are configured (i.e., the pilot interval is longer). When the pilot signal obtained under this pilot interval is used to update the coefficients of the MIMO equalizer, the update speed of the MIMO equalizer can be reduced, thereby reducing the computational complexity of the MIMO equalizer and thereby reducing the power consumption of the entire polarization tracking process.

[0052] As a further design of the present invention, Figure 3 As shown, it also includes:

[0053] Compare the current polarization rotation state speed Δφ with the preset threshold φ Thresh For comparison:

[0054] When Δφ≤φ Thresh When the automatic polarization controller is enabled, polarization tracking is performed using the automatic polarization controller; where the threshold φ Thresh Set based on experience;

[0055] When Δφ>φ Thresh When , the MIMO equalizer is enabled and the aforementioned MIMO equalizer is used for polarization tracking. The MIMO equalizer herein is the improved MIMO equalizer in the embodiment of the present invention, i.e., a MIMO equalizer that dynamically configures the pilot interval required to track polarization state changes based on the currently sensed polarization rotation state velocity Δφ.

[0056] Specifically, the calculation formula for the current polarization rotation state velocity Δφ is:

[0057]

[0058] Where V1 and V2 are the voltages corresponding to the two polarization states of the received optical signal after polarization splitting, which are further converted into electrical signals; Δt represents the sampling period for sensing the current polarization rotation state speed; express The change between the initial and final moments of a sampling period.

[0059] Before the MIMO equalizer performs polarization tracking, the received optical signal is converted into an electrical signal and polarization tracking is performed on the electrical signal.

[0060] The method also includes: modulating the communication signal onto a single-frequency optical carrier at the communication transmitting end to obtain an optical signal, and sending the optical signal to the communication receiving end through an optical fiber link.

[0061] The polarization tracking method of the present invention makes a judgment by sensing the current polarization rotation state speed Δφ. When the current polarization rotation state speed Δφ is low, an automatic polarization controller is enabled. The automatic polarization controller has a low algorithm complexity and is easy to implement low-power polarization tracking. When the current polarization rotation state speed Δφ is high, a MIMO equalizer is used for polarization tracking to achieve fast polarization tracking. In this way, flexible configuration of polarization rotation processing with a high dynamic range is achieved, without the need to use a more complex MIMO equalizer even at low speeds, and further reducing the power consumption of the entire polarization tracking process.

[0062] Example 2

[0063] like Figure 4 As shown, an embodiment of the present invention provides a polarization tracking device, comprising: a polarization sensing signal processing module, a dynamic pilot interval calculation unit, a frame synchronization unit, and a MIMO equalizer; wherein the polarization sensing signal processing module comprises a polarization rotation state speed calculation unit and a comparison unit;

[0064] The polarization rotation state speed calculation unit is used to calculate the current polarization rotation state speed Δφ based on the received optical signal at the communication receiving end;

[0065] The dynamic pilot interval calculation unit is used to dynamically calculate the pilot interval ΔL currently required by the MIMO equalizer according to the current polarization rotation state speed Δφ Rx In the embodiment of the present invention, when Δφ>φ Thresh When the MIMO equalizer is used, the pilot interval ΔL currently required is dynamically calculated. Rx ;

[0066] The frame synchronization unit is used to determine the currently required pilot interval ΔL Rx The starting point in the received signal frame to achieve frame synchronization;

[0067] After frame synchronization, the MIMO equalizer starts from ΔL Rx Starting from the starting point, the interval length ΔL Rx The pilot signal is obtained to calculate the update coefficients of the MIMO equalizer, which is then butterfly filtered with the received optical signal to achieve polarization tracking.

[0068] Furthermore, it also includes an automatic polarization controller; a comparison unit is used to compare the current polarization rotation state speed Δφ with a preset threshold φ Thresh For comparison: When Δφ≤φ Thresh When Δφ>φ, the automatic polarization controller is enabled and polarization tracking is performed using the automatic polarization controller;Thresh When the MIMO equalizer is enabled to perform polarization tracking, the pilot interval required for the MIMO equalizer to perform polarization tracking is a dynamically configured pilot interval. For specific implementation methods, please refer to the above specific description.

[0069] Specifically, in an embodiment of the present invention, the polarization rotation state speed calculation unit includes: a polarization beam splitter, a photodetector, and a calculation unit; wherein the polarization beam splitter is used to split the received optical signal into two optical signals with different polarization states, and the optical signal of each polarization state is subjected to corresponding photoelectric conversion by the corresponding photodetector to obtain a corresponding electrical signal, and after signal processing, the voltages V1 and V2 corresponding to each electrical signal are obtained; the calculation unit calculates the voltage V1 and V2 corresponding to each electrical signal according to the formula Calculate the current polarization rotation state speed Δφ.

[0070] The invention also includes a coupler for splitting the optical signal received by the communication receiving end, a part of which is used as the input of the polarization rotation state speed calculation unit to calculate the current polarization rotation state speed Δφ; the other part is used to calculate the current polarization rotation state speed Δφ according to Δφ and φ Thresh The relationship between the optical signals is input to an automatic polarization controller or MIMO equalizer for polarization tracking. Prior to input to the MIMO equalizer, the optical signal must be converted into an analog electrical signal, and then into a digital electrical signal for other digital signal processing. In this embodiment of the present invention, the coupler is a 95:5 coupler, with 5% of the optical signal entering the polarization rotation state speed calculation unit and 95% of the optical signal entering the automatic polarization controller or MIMO equalizer for polarization tracking.

[0071] The system also includes a communication optical signal generating unit for modulating the communication signal onto a single-frequency optical carrier at the communication transmitting end to generate an optical signal, and transmitting the optical signal to the communication receiving end via an optical fiber link. The optical fiber used in the optical fiber link can be a single-mode optical fiber or a large effective area optical fiber.

[0072] The specific implementation of the above-mentioned related units and modules can be found in the description of the corresponding steps in the above-mentioned embodiment 1, which will not be repeated here.

[0073] Example 3

[0074] An embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the polarization tracking method described in the above-mentioned embodiment 1 is implemented. For related technical solutions, please refer to the corresponding description in embodiment 1 and will not be repeated here.

[0075] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A polarization tracking method, comprising a MIMO equalizer, characterized in that: include: At the communication receiving end, the current polarization rotation state velocity Δφ is calculated based on the received optical signal; Calculate the pilot interval ΔL currently required by the MIMO equalizer according to the polarization rotation state speed Δφ Rx ; Among them, Δφ and ΔL Rx Inversely proportional relationship; Determine the currently required pilot interval ΔL Rx The starting point in the received signal frame is used to achieve frame synchronization; wherein the received signal is an electrical signal after the received optical signal is photoelectrically converted and analog-to-digital converted; After frame synchronization, the MIMO equalizer starts from the starting point and the interval ΔL Rx Obtaining a pilot signal in the signal frame to calculate update coefficients of the MIMO equalizer, and then performing butterfly filtering on the received signal to achieve polarization tracking; Δφ and ΔL Rx Satisfy between: ΔL Rx =ceil(ΔL Tx *f max / Df) Among them, ceil represents a positive integer greater than or equal to, ΔL Tx represents the pilot interval inserted into the optical signal at the communication transmitter, φ max Indicates that the pilot interval is ΔL Tx The maximum polarization tracking speed supported by the pilot. * indicates a multiplication operation.

2. The polarization tracking method according to claim 1, wherein: Determine the currently required pilot interval ΔL Rx The starting point in the received signal frame to achieve frame synchronization, including: ΔL in the received signal frame Rx Slide within the symbol length to take the 1st to ΔLth Tx symbols as the starting point, with ΔL Tx Take N groups of pilots for the interval; Perform cross-correlation calculations on the N groups of pilots and the pilot sequence inserted into the optical signal at the communication transmitting end, and take the symbol corresponding to the maximum cross-correlation value as the currently required pilot interval ΔL Rx The starting point in the received signal frame to achieve frame synchronization; where N = ΔL Rx / ΔL Tx .

3. The polarization tracking method according to claim 1, wherein: The polarization rotation state speed Δφ is greater than a preset threshold φ Thresh ; And when Δφ≤φ Thresh When the polarization is detected, an automatic polarization controller is used for polarization tracking.

4. The polarization tracking method according to claim 3, wherein: The calculation formula of the polarization rotation state velocity Δφ is: Wherein, V1 and V2 are the voltages corresponding to the two polarization states of the optical signal obtained by polarization splitting of the received optical signal converted into electrical signals; Δt represents the sampling period for sensing the current polarization rotation state speed; express The change between the initial and final moments of a sampling period.

5. A polarization tracking device based on a MIMO equalizer, comprising a MIMO equalizer, characterized in that: The method for performing the polarization tracking method according to any one of claims 1 to 4 comprises: a polarization rotation state speed calculation unit, configured to calculate, at a communication receiving end, a current polarization rotation state speed Δφ based on a received optical signal; A dynamic pilot interval calculation unit is used to calculate the pilot interval ΔL currently required by the MIMO equalizer according to the polarization rotation state speed Δφ Rx ; Among them, Δφ and ΔL Rx Inversely proportional relationship; Frame synchronization unit, used to determine the currently required pilot interval ΔL Rx At the starting point in the received signal frame, to achieve frame synchronization; wherein the received signal is an electrical signal obtained by photoelectric conversion of the received optical signal; After frame synchronization, the MIMO equalizer starts from the starting point and the interval ΔL Rx A pilot signal in the signal frame is obtained to calculate the update coefficient of the MIMO equalizer, and then butterfly filtering is performed on the received signal to achieve polarization tracking.

6. The polarization tracking device according to claim 5, wherein: The polarization rotation state speed Δφ is greater than a preset threshold φ Thresh ; And when Δφ≤φ Thresh When the polarization tracking device is used, it also includes an automatic polarization controller for polarization tracking.

7. The polarization tracking device according to claim 6, wherein: Also included is a coupler; The coupler is used to split the received optical signal into two parts, one part of the light is used to input into the polarization rotation state speed calculation unit to calculate the current polarization rotation state speed Δφ; the other part of the light is used to calculate the current polarization rotation state speed Δφ when Δφ≤φ Thresh When Δφ>φ Thresh , it is input to the MIMO equalizer for polarization tracking.

8. The polarization tracking device according to claim 7, wherein: It also includes a communication optical signal generating unit, which is used to modulate the communication signal onto a single-frequency optical carrier at the communication transmitting end to obtain an optical signal, and send it to the communication receiving end through an optical fiber link.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the polarization tracking method according to any one of claims 1 to 4 is implemented.

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