Method and apparatus for tracking and recovering polarization state

Abstract

To provide polarization state tracking recovery method and device.SOLUTION: A polarization state tracking recovery device includes at least a fitting unit that obtains a fitting plane by fitting a Stokes vector corresponding to a predetermined symbol of two polarization states in a double-polarized multiplex optical reception signal on a Poincare sphere, a first matrix calculation unit that calculates a first compensation matrix for polarization-dependent loss compensation in a Jones space, and a second matrix calculation unit that computes a demultiplexing matrix for polarization demultiplexing in the Jones space. The demultiplexing matrix is calculated by rotating the fitting plane after moving the center to the origin until the normal vector is parallel to the first axis of the Stokes space, and rotating the fitting plane after moving the center to the origin to a plane consisting of a second axis and a third axis of the Stokes space.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to the field of communication technologies.

Background Art

[0002] Coherent optical communication has become the main technology of next-generation optical communication systems. In order to improve the communication rate, on the one hand, the frequency spectrum bandwidth of the system can be increased, and on the other hand, the frequency spectrum utilization rate can be improved. In order to improve the frequency spectrum utilization rate, from simple amplitude modulation to higher-order quadrature amplitude modulation, the number of bits carried by each symbol in the system can be increased. Then, by adopting polarization division multiplexing technology to simultaneously transmit two paths of orthogonal polarization states, the transmission rate can be improved. However, there are losses related to various polarizations in the optical fiber transmission link, such as losses due to optical fibers, chromatic dispersion, and polarization effects. These losses may cause distortion of the dual-polarization modulation optical signal. Among them, due to the influence of the undesirable external environment of the optical fiber occurring in the manufacturing process, the directions of the polarization principal axes (fast axis and slow axis) at different locations of the optical fiber may also be different. Therefore, since the state of polarization (SOP) of the received dual-polarization modulation optical signal can usually change, it may cause rotation of the state of polarization (RSOP), and this change is generally slow. However, in some cases, such as lightning strikes, the rotation rate of the SOP can reach the megahertz level. Also, the polarization-dependent loss (PDL) existing in the transmission link can also change the SOP of the dual-polarization modulation optical signal. For a polarization multiplexing system, it is necessary to realize signal polarization separation (demultiplexing) in the received signal at the receiving end. Among them, in order to recover the SOP of the received signal, it is necessary to track and recover the SOP under the effect of PDL.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The inventor has discovered the following. That is, in the conventional method, one inverse matrix (rotation matrix) can be found from among the features distributed in the Stokes domain using the polarization multiplexed signal to recover the original polarization state. However, in the process of calculating the inverse matrix, since PDL compensation is performed after polarization demultiplexing, the computational complexity is quite high.

[0004] Furthermore, the inventor has further discovered the following. That is, in the conventional method, first, the received signal is mapped to a point on the Poincare sphere to fit one fitting plane, and then the polarization demultiplexing can be completed by rotating the fitting plane until the normal vector of the fitting plane is parallel to one axis of the Stokes space. However, in the conventional method, calculations are performed using all the points obtained by mapping the received signal onto the Poincare sphere. Thus, there may be a problem that the direction of the normal vector becomes ambiguous, and the exchange of two polarization states may also be caused after demultiplexing due to the reverse direction of the normal vector.

[0005] Furthermore, the inventor has also discovered the following. That is, in the conventional inverse matrix calculation process, only PDL compensation and polarization demultiplexing are considered, and residual phase delay compensation is not considered, so the phase noise in the demultiplexed signal may be increased.

[0006] In view of at least one of the above problems, embodiments of the present invention provide a polarization state tracking and recovery method and apparatus.

Means for Solving the Problems

[0007] According to a first aspect of an embodiment of the present invention, a polarization state tracking and recovery apparatus is provided, wherein the apparatus includes A conversion unit that converts a Jones vector composed of predetermined symbols of two polarization states in a dual-polarization multiplexing optical received signal into a Stokes vector; A fitting unit that performs fitting on the Stokes vector corresponding to each of the predetermined symbols on the Poincaré sphere to obtain a fitting plane; A first matrix calculation unit that calculates a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere; A second matrix calculation unit that calculates an inverse multiplexing matrix for polarization demultiplexing in the Jones space, wherein the fitting plane after moving the center to the origin is rotated until the normal vector of the fitting plane is parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane composed of the second axis and the third axis of the Stokes space to calculate the inverse multiplexing matrix; A first calculation unit that calculates a first rotation matrix of the polarization state (SOP) corresponding to each of the predetermined symbols based on the first compensation matrix and the inverse multiplexing matrix; A second calculation unit that calculates a second rotation matrix of the polarization state (SOP) at different times of the optical received signal based on the first rotation matrix of the polarization state (SOP) corresponding to each of the predetermined symbols; and A recovery unit that recovers the optical received signals of the two polarization states in the optical received signal by multiplying the two-dimensional vector composed of the two polarization states in the optical received signal by the second rotation matrix of the polarization state.

[0008] According to a second aspect of an embodiment of the present invention, a polarization state tracking and recovery device is provided, wherein the device includes A conversion unit that converts a Jones vector composed of pilot symbols of two polarization states in a dual-polarization multiplexing optical received signal into a Stokes vector; A fitting unit that performs fitting on the Poincaré sphere for the Stokes vector corresponding to each of the pilot symbols to obtain a fitting plane; A matrix calculation unit that calculates a first compensation matrix for polarization-dependent loss (PDL) compensation in Jones space, calculates an inverse multiplexing matrix for polarization demultiplexing in Jones space based on the pilot symbols, calculates the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and rotates the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and calculates the inverse multiplexing matrix by rotating the fitting plane rotation to the plane composed of the second axis and the third axis of the Stokes space; A first calculation unit that calculates a first rotation matrix of the state of polarization (SOP) corresponding to each of the pilot symbols based on the first compensation matrix and the inverse multiplexing matrix; A second calculation unit that calculates a second rotation matrix of the state of polarization (SOP) at different times of the optical reception signal based on the first rotation matrix of the state of polarization corresponding to each of the pilot symbols; and A recovery unit that recovers the optical reception signals of the two states of polarization in the optical reception signal by multiplying the two-dimensional vector composed of the two states of polarization in the optical reception signal by the second rotation matrix of the state of polarization.

[0009] According to a third aspect of an embodiment of the present invention, a state of polarization tracking and recovery device is provided, wherein the device includes A conversion unit that converts a Jones vector composed of two states of polarization of a dual-polarization multiplexed optical reception signal into a Stokes vector; A fitting unit that performs fitting on the Poincaré sphere for the Stokes vector corresponding to each of the predetermined symbols to obtain a fitting plane; Calculate a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, calculate a demultiplexing matrix for polarization demultiplexing in the Jones space, move the center of the fitting plane to the origin of the Poincaré sphere to calculate the first compensation matrix, and rotate the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and move the fitting plane to the plane composed of the second and third axes of the Stokes space to calculate the demultiplexing matrix; a matrix calculation unit; A third matrix calculation unit that calculates a second compensation matrix for phase compensation in the Jones space; A first calculation unit that calculates a first rotation matrix of the state of polarization (SOP) corresponding to each of the predetermined symbols based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix; A second calculation unit that calculates a second rotation matrix of the state of polarization at different times of the optical reception signal based on the first rotation matrix of the state of polarization (SOP) corresponding to each of the predetermined symbols; and A recovery unit that recovers the optical reception signals of the two states of polarization in the optical reception signal by multiplying the two-dimensional vector composed of the two states of polarization in the optical reception signal by the second rotation matrix of the state of polarization.

[0010] One of the advantageous effects of the present invention is as follows: that is, in the process of calculating the inverse matrix, by performing PDL compensation before polarization demultiplexing, the calculation complexity can be reduced.

[0011] One of the advantageous effects of the present invention is as follows: that is, since the direction of the normal vector of the fitting plane can be determined using pilot symbols, the problem of ambiguity in the direction of the normal vector can be solved, and the exchange of the two states of polarization after demultiplexing will not be caused.

[0012] One of the advantageous effects of the present invention is as follows: that is, by compensating for the residual phase delay after polarization demultiplexing, the phase noise of the demultiplexed signal can be reduced.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying out the Invention

[0014] Hereinafter, with reference to the accompanying drawings, preferred embodiments for carrying out the present invention will be described in detail.

[0015] <Embodiment of the First Aspect> In an embodiment of the present invention, a polarization state tracking and recovery device is provided, and the polarization state tracking and recovery device is provided at the optical receiver end of an optical communication system.

[0016] FIGS. 1A and 1B are diagrams showing an optical communication system in an embodiment of the present invention. As shown in FIG. 1A, the optical communication system 10 includes an optical transmitter 11, an optical fiber link 12, an optical receiver 13, and a signal processor 14. The polarization state tracking and recovery device 100 can realize polarization demultiplexing by performing processing on the received signal after receiving signal processing.

[0017] In this embodiment, the optical communication system 10 may be a back-to-back system. In other words, as shown in FIG. 1B, the optical communication system 10 may not include the optical fiber link 12 and may be configured by directly connecting the optical transmitter 11 and the optical receiver 13.

[0018] In this embodiment, the optical transmitter 11, the optical receiver 13, and the signal processor 14 may all use various existing structures. The embodiments of the present invention do not limit the specific structures thereof. For example, the signal processor 14 may include a clock recovery module, a chromatic dispersion compensation module, and a receiver IQ imbalance compensation module, but the detailed description thereof is omitted here.

[0019] FIG. 2A is a diagram showing a polarization state tracking and recovery device according to an embodiment of the present invention. For example, the polarization state tracking and recovery device is the polarization state tracking and recovery device 100 shown in FIGS. 1A-1B. As shown in FIG. 2A, the polarization state tracking and recovery device 100 includes the following.

[0020] Conversion unit 201: Converts the Jones vector composed of two polarization states of a dual-polarization multiplexed optical reception signal into a Stokes vector from a predetermined symbol; Fitting unit 202: Performs fitting on the Stokes vector corresponding to each of the predetermined symbols on the Poincaré sphere to obtain a fitting plane; First matrix calculation unit 203: Calculates a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, and calculates the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere; Second matrix calculation unit 204: Calculates a demultiplexing matrix for polarization demultiplexing in the Jones space. Among them, the fitting plane after moving the center to the origin is rotated until the normal vector of the fitting plane is parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane composed of the second axis and the third axis of the Stokes space to calculate the demultiplexing matrix; First calculation unit 205: Calculates an SOP first rotation matrix corresponding to each of the predetermined symbols based on the first compensation matrix and the demultiplexing matrix; Second calculation unit 206: Calculates an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each predetermined symbol; Recovery unit 207: Multiplies the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0021] In this way, the fitting plane after being moved to the origin is rotated until its normal vector is parallel to the first axis of the Stokes space, and the fitting plane after being moved to the origin is rotated to the plane formed by the second axis and the third axis of the Stokes space, thereby calculating the demultiplexing matrix for polarization demultiplexing. That is, since PDL compensation is performed before polarization demultiplexing, the computational complexity can be reduced.

[0022] In some embodiments, the predetermined symbol used in the conversion unit 201 may be a pilot symbol and / or a payload symbol in the received signal, but this embodiment is not limited thereto. When the predetermined symbol is a pilot symbol, it may be a quadrature phase shift keying (QPSK) symbol, or other types of modulation symbols, such as a binary phase shift keying (BPSK) symbol, etc. Here, a comprehensive description thereof is omitted.

[0023] In some embodiments, when the predetermined symbol is a QPSK pilot symbol, this embodiment further provides a polarization state tracking and recovery device. FIG. 2B is a diagram showing the polarization state tracking and recovery device in an embodiment of the present invention. For example, the polarization state tracking and recovery device is the polarization state tracking and recovery device 100 shown in FIGS. 1A-1B. As shown in FIG. 2B, the polarization state tracking and recovery device 100 includes a conversion unit 201′, a fitting unit 202′, a first matrix calculation unit 203′, a second matrix calculation unit 204′, a first calculation unit 205′, a second calculation unit 206′, and a recovery unit 207′. Since the implementation manners of these units are the same as those of the conversion unit 201, the fitting unit 202, the first matrix calculation unit 203, the second matrix calculation unit 204, the first calculation unit 205, the second calculation unit 206, and the recovery unit 207 in FIG. 2A, a detailed description thereof is omitted here.

[0024] The device may further include the following.

[0025] Extraction unit 208': Extract two pilot symbols in two polarization states from the dual-polarization multiplexed optical reception signal; Block division unit 209': Perform block division on the pilot symbol, and each block contains a first predetermined number of pilot symbols.

[0026] In some embodiments, the dual-polarization multiplexed optical reception signal may be the signal after being processed by the signal processing device 14 in FIGS. 1A-1B, or may be the signal received by the optical receiver 13. However, the present embodiment is not limited thereto. Since the pilot symbol is known and is distributed in the data of each frame at a certain time interval, the extraction unit can extract the pilot symbol based on the known frame structure. For the specific method, reference can be made to the prior art. For example, the position of the pilot symbol in two polarization states in the dual-polarization multiplexed optical reception signal can be identified and extracted by using the training sequence or the feature of the difference between the pilot symbol and the effective payload symbol (such as Peak to Average Power Ratio, etc.) in the frame structure. However, the detailed description thereof is omitted here.

[0027] In some embodiments, block division can be performed on pilot symbols. For example, the block division unit 209' performs block division on pilot symbols arranged in chronological order. Each block contains a first predetermined number N of pilot symbols. The first predetermined number depends on different link conditions and can be determined based on parameter scanning or empirical values, but this embodiment is not limited thereto. FIG. 3 is a diagram showing block division. As shown in FIG. 3, the first predetermined number N of pilot symbols included in the nth block includes the pilot symbols from the (n - ((N - 1) / 2))th pilot symbol to the (n + ((N - 1) / 2))th pilot symbol. The time window of each block moves in a sliding manner, moving one pilot symbol each time. That is, the first predetermined number N of pilot symbols included in the (n + 1)th block includes the pilot symbols from the (n - ((N - 1) / 2) + 1)th pilot symbol to the (n + ((N - 1) / 2) + 1)th pilot symbol, and the rest can be analogized based on this. Here, the detailed description is omitted. Among them, n and N are positive integers.

[0028] In some embodiments, the conversion unit 201, the fitting unit 202, and the first matrix calculation unit 203 perform processing on the pilot symbols in each block with each block as a unit. That is, the N pilot symbols in the nth block are used to estimate the rotation matrix corresponding to the nth pilot symbol. Since the processing of each block by the conversion unit 201, the fitting unit 202, and the first matrix calculation unit 203 is the same, the following will take the nth block as an example for detailed explanation.

[0029] In some embodiments, the conversion unit 201 converts the Jones vector composed of the pilot symbols of two polarization states in the nth block of the dual-polarization multiplexed optical reception signal into a Stokes vector. Among them, the Jones vector and the Stokes vector are two representation methods of polarized light. The Jones vector is

Number

[0030] In some embodiments, the fitting unit 202 performs fitting on the Stokes vectors corresponding to all the pilot symbols in the nth block on the Poincaré sphere, and obtains the fitting plane corresponding to each block. FIG. 4 is a configuration diagram of the fitting unit 202. As shown in FIG. 4, the fitting unit 202 includes the following.

[0031] Component sorting module 401: Sort the QPSK pilot symbols in the nth block based on the positions of the QPSK pilot symbols on the Poincaré sphere in the nth block; Calculation module 402: Calculate the average value of each group to obtain the center point; Fitting module 403: Perform fitting on the center point of each group to obtain the fitting plane.

[0032] In some embodiments, one point on the Poincaré sphere represents one polarization state. For a QPSK pilot symbol without distortion, there are four polarization states SOPs on the Poincaré sphere, which are A(0, 1, 0), B(0, 0, 1), C(0, -1, 0), and D(0, 0, -1) respectively, and these are regarded as four reference points. FIG. 5 is a diagram showing the Poincaré sphere. As shown in FIG. 5, for the QPSK pilot symbols without distortion, each (External 3) TIFF0007711424000006.tif18170 axis and (External 4) TIFF0007711424000007.tif18170 axis. For the polarization state (position) of the QPSK pilot symbol on the Poincaré sphere in the nth block extracted by the extraction module 208' by the sorting module 401, sorting is performed, which includes determining the reference point corresponding to each pilot symbol in the nth block and grouping the pilot symbols with the same reference point into one group. Among them, since the transmitted QPSK pilot symbol information is known, after specifying the position of the QPSK pilot symbol in the frame structure, the reference point corresponding to each pilot symbol can be determined, that is, the QPSK pilot symbol without distortion corresponding to each pilot symbol in the received signal can be determined, and the points with the same reference point can be grouped into one group. As shown in FIG. 5, the pilot symbols in the nth block can be divided into four groups (four groups of SOPs). The calculation module 402 calculates the average values A', B', C', and D' of each group as the center points of each group, and by performing fitting on A', B', C', and D', a fitting plane can be obtained. The center of the fitting plane is the average value of the four center points A', B', C', and D'.

[0033] In some embodiments, as can be understood from the principle of the Poincaré sphere, the center of the fitting plane is displaced from the Poincaré sphere due to the effect of PDL. Therefore, by moving the center of the fitting plane to the origin position, a first compensation matrix for PDL compensation can be calculated. The normal vector of the fitting plane is (Outer 5) By rotating it until it is parallel to the axis of TIFF0007711424000008.tif17170, an inverse multiplexing matrix for polarization demultiplexing can be calculated. However, a detailed description of the principle will be omitted here.

[0034] In some embodiments, the first matrix calculation unit 203 calculates a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space. Among them, the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere. FIG. 6 is a diagram showing the process of the PDL compensation. As shown in FIG. 6, first, compensation is performed for the distance d1 that the center moves along the (Outer 6) axis of TIFF0007711424000009.tif19170, and then, (Outer 7) compensation is performed for the distance d2 that the center moves along the axis of TIFF0007711424000010.tif17170. Then, (Outer 8) compensation is performed for the distance d3 that the center moves along the axis of TIFF0007711424000011.tif14170. As a result, it (the center) can be made to overlap with the origin. The calculation formula of the first compensation matrix in this Jones space (two-dimensional matrix) can be shown by the following formula (1).

Equation

[0035] In some embodiments, after multiplying the received signal by the first compensation matrix, PDL compensation can be achieved.

[0036] In some embodiments, the second matrix calculation unit 204 calculates a demultiplexing matrix for polarization demultiplexing in the Jones space, wherein the fitting plane after moving the center to the origin is rotated until the normal vector thereof is parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane formed by the second axis and the third axis of the Stokes space to calculate the demultiplexing matrix. Thus, the embodiments of the present invention first move the center of the fitting plane to the origin, and then rotate the fitting plane until the normal vector thereof is parallel to the first axis of the Stokes space, and rotate the fitting plane after moving the center to the origin to the plane formed by the second axis and the third axis of the Stokes space. In other words, in this embodiment, polarization demultiplexing is performed after PDL compensation, which is different from the conventional solution that performs polarization demultiplexing first and then PDL compensation (that is, first calculate the center of the fitting plane once, and then calculate the normal vector of the fitting plane based on this, and rotate the fitting plane until the normal vector thereof is parallel to the first axis of the Stokes space (that is, perform polarization demultiplexing), then calculate the center of the fitting plane again, and then perform PDL compensation). By reducing the number of calculations of the center point of the fitting plane from two times to one time, the computational complexity can be reduced.

[0037] In some embodiments, the second matrix calculation unit 204 calculates the normal vector of the fitting plane. For example, the normal vector of the fitting plane is calculated based on the least squares method using all points (polarization states) on the Poincare sphere of the dual-polarization multiplexed optical reception signal. Then, the included angle between the normal vector and the first axis is calculated, and the rotation axis is obtained such that the first axis is rotated to overlap with the normal vector direction, thereby obtaining the above demultiplexing matrix.

[0038] In some embodiments, to avoid the problem of the ambiguity of the normal vector, the second matrix calculation unit 204 can determine the normal vector of the fitting plane based on the pilot symbol. For example, based on the center points of each of the above-mentioned sets (the QPSK pilot symbols belong to 4 sets on the Poincaré sphere), the normal vector of the fitting plane is calculated, the included angle between the normal vector and the first axis is calculated, the rotation axis for rotating the first axis vector to the normal vector is determined, and then, based on the included angle and the rotation axis, the demultiplexing matrix for polarization demultiplexing is calculated.

[0039] For example, determining the normal vector of the fitting plane based on the pilot symbol includes performing a cross multiplication of vectors from the origin of the Poincaré sphere to at least one pair of adjacent center points, and determining the normal vector based on the result of the cross multiplication of at least one pair of vectors. Among them, the order of the cross multiplication of at least one pair of adjacent two center points is determined according to the counterclockwise order on the plane formed by the second axis and the third axis of the reference point. For example, the center points of each of the above-mentioned sets are A′, B′, C′, D′ (in the counterclockwise order on the plane formed by the second axis and the third axis) respectively, the origin is denoted as O, and the cross multiplication of vectors (External 9) TIFF0007711424000013.tif16170 or (External 10) TIFF0007711424000014.tif16170 (External 11) TIFF0007711424000015.tif17170 or (External 12) TIFF0007711424000016.tif16170 is performed, and the normal vector is determined based on the result of at least one pair of cross multiplications. For example, normalization is performed on the result of one pair of cross multiplications among them, or the average value of the results of at least one pair of cross multiplications, so as to obtain a normal vector without an ambiguous direction (External 13) TIFF0007711424000017.tif17170 can be obtained. The normal vector (External 14) TIFF0007711424000018.tif and 16170 (External 15) Calculate the included angle α between TIFF0007711424000019.tif and the 13170 axis, and perform the cross multiplication of the first axis vector and the normal vector (External 16) Perform TIFF0007711424000020.tif and 15170, and determine the result of normalization as the rotation axis vector (External 17) TIFF0007711424000021.tif and 14170, and based on α and (External 18) TIFF0007711424000022.tif and 13170, the inverse multiplexing matrix for polarization demultiplexing in the Jones space (two-dimensional matrix) can be calculated. Specifically, Equation 2) below can be referred to. [Number]

[0040] Among them, [Number] where (σ1, σ2, σ3) is from the above Pauli matrix, I represents the identity matrix, (External 19) TIFF0007711424000025.tif and 17170 is a unit vector (External 20) TIFF0007711424000026.tif represents the three components of 17170.

[0041] In some embodiments, the first calculation unit 205 calculates the SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix J1 and the inverse multiplexing matrix J2. For example, the result of J2×J1 can be used as the SOP first rotation matrix corresponding to the nth pilot symbol.

[0042] The above has been described by taking as an example that the conversion unit 201, the fitting unit 202, and the first matrix calculation unit 203 perform processing on the pilot symbols in the n-th block in units of each block. However, the conversion unit 201, the fitting unit 202, and the first matrix calculation unit 203 can sequentially perform similar processing on the pilot symbols in each block, whereby the SOP first rotation matrix corresponding to each pilot symbol can be obtained.

[0043] In some embodiments, the second calculation unit 206 calculates the SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each predetermined symbol (for example, a pilot symbol), and calculates, for example, the SOP third rotation matrix corresponding to the non-pilot symbols (for example, payload symbols) of the optical reception signal by an interpolation method (algorithm) (for example, linear interpolation, etc.). The SOP first rotation matrix and the SOP third rotation matrix are combined to form the SOP second rotation matrix at different times of the optical reception signal. For example, each pilot symbol corresponds to the SOP first rotation matrix X, and by performing interpolation on the first element X(1,1) of these matrices, the first element Y(1,1) of the SOP third rotation matrix Y corresponding to the non-pilot symbol can be obtained, and the rest can be analogized based on this. However, the detailed description thereof is omitted here.

[0044] In some embodiments, the recovery unit 207 multiplies the SOP second rotation matrix by the two-dimensional vector composed of two polarization states in the optical reception signal to recover the optical reception signals of the two polarization states in the optical reception signal.

[0045] As can be seen from the above embodiments, the fitting plane after moving the center to the origin is rotated until its normal vector is parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane composed of the second axis and the third axis of the Stokes space, thereby calculating the demultiplexing matrix for polarization demultiplexing, that is, in order to perform PDL compensation before polarization demultiplexing, the computational complexity can be reduced.

[0046] <Embodiment of the second side> In the embodiment of the present invention, a polarization state tracking and recovery device is provided, and the polarization state tracking and recovery device is provided at the optical receiver end of the optical communication system. It should be noted that the difference from the embodiment of the first aspect is that further phase compensation is performed after polarization demultiplexing.

[0047] FIG. 7 is a diagram showing a polarization state tracking and recovery device in an embodiment of the present invention. For example, the polarization state tracking and recovery device is the polarization state tracking and recovery device 100 shown in FIGS. 1A-1B. As shown in FIG. 7, the polarization state tracking and recovery device 100 includes a conversion unit 701, a fitting unit 702, a first matrix calculation unit 703, a second matrix calculation unit 704, a second calculation unit 706, and a recovery unit 707. Since the implementation manners of these units are the same as those of the conversion unit 201, the fitting unit 202, the first matrix calculation unit 203, the second matrix calculation unit 204, the second calculation unit 206, and the recovery unit 207 in the embodiment of the first aspect, the duplicate description is omitted here.

[0048] In some embodiments, the polarization state tracking and recovery device 100 may further include an extraction unit (optional; not shown) and a blocking unit (optional; not shown). For the implementation manners of these two units, reference can also be made to the embodiment of the first aspect, so the detailed description is omitted here.

[0049] In some embodiments, as shown in FIG. 7, the polarization state tracking and recovery device 100 may further include the following.

[0050] Third row-column calculation unit 708: calculates a second compensation matrix for phase compensation in the Jones space; and First calculation unit 705: calculates an SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix.

[0051] In some embodiments, after PDL compensation and polarization demultiplexing are performed, the fitting plane is, again, (Outer 21) TIFF0007711424000027.tif18170 axis and (Outer 22) The plane can rotate to a plane composed of the TIFF0007711424000028.tif15170 axis, where the fitting plane rotated to the plane composed of the second axis and the third axis is continuously rotated until the center point of each group (the QPSK pilot symbols belong to 4 groups on the Poincaré sphere) overlaps with its respective reference point, so that the second compensation matrix can be calculated. For example, the third row-column calculation unit 708 determines the rotation angle based on the included angle between the center point and the reference point of each group, and calculates the second compensation matrix in the Jones space (two-dimensional matrix) of the phase compensation based on the rotation angle and the rotation axis, where the rotation axis is the first axis. Specifically, since Equation 2) above can be referenced, the detailed description is omitted here.

[0052] In some embodiments, the first calculation unit 705 calculates an SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix J1, the inverse multiplexing matrix J2, and the second compensation matrix J3. For example, the result of J3×J2×J1 can be used as the SOP first rotation matrix corresponding to the nth pilot symbol.

[0053] As can be seen from the above embodiments, in this embodiment, polarization demultiplexing and phase delay compensation are further performed after PDL compensation. This is because, compared with performing polarization demultiplexing and phase delay compensation first and then PDL compensation (that is, first calculating the center of the fitting plane once, and then calculating the normal vector of the fitting plane based on this, and rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space (that is, performing polarization demultiplexing), then calculating the center of the fitting plane again, and compensating for the residual phase delay between the two polarization states, and then calculating the center of the fitting plane once more, and then performing PDL compensation), by reducing the number of calculations of the center point of the fitting plane from three times to one time, the computational complexity can be reduced. Also, by compensating for the residual phase delay after polarization demultiplexing, the phase noise of the demultiplexed signal can also be reduced.

[0054] <Embodiment of the third side> In the embodiment of the present invention, a polarization state tracking and recovery device is provided, and the polarization state tracking and recovery device is provided at the optical receiver end of an optical communication system. The difference from the embodiment of the first aspect is that in this embodiment, a predetermined symbol is a pilot symbol, and the demultiplexing matrix in the Jones space of polarization demultiplexing is calculated based on the pilot symbol, and the execution order of PDL compensation and polarization demultiplexing is not limited.

[0055] FIG. 8 is a diagram showing a polarization state tracking and recovery device in an embodiment of the present invention. For example, the polarization state tracking and recovery device is the polarization state tracking and recovery device 100 shown in FIGS. 1A-1B. As shown in FIG. 8, the polarization state tracking and recovery device 100 includes the following.

[0056] Conversion unit 801: Converts the Jones vector composed of the pilot symbols of the two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; Fitting unit 802: Perform fitting on the Poincaré sphere for the Stokes vectors corresponding to each pilot symbol to obtain a fitting plane; Matrix calculation unit 803: Calculate a first compensation matrix for polarization-dependent loss compensation in the Jones space, calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space based on the pilot symbol, calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and rotate the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and calculate the inverse multiplexing matrix by rotating the fitting plane to the plane formed by the second and third axes of the Stokes space; First calculation unit 804: Calculate an SOP first rotation matrix corresponding to each pilot symbol based on the first compensation matrix and the inverse multiplexing matrix; Second calculation unit 805: Calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each pilot symbol; Recovery unit 806: Multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0057] In some embodiments, for the implementation manners of the conversion unit 801, fitting unit 802, first calculation unit 804, second calculation unit 805, and recovery unit 806, since the implementation manners of the conversion unit 201, fitting unit 202, first calculation unit 205, second calculation unit 206, and recovery unit 207 when a predetermined symbol is a pilot symbol in the embodiments of the first aspect can be referred to, the detailed description thereof is omitted here.

[0058] In some embodiments, the polarization state tracking and recovery device 100 may further include an extraction unit (optional; not shown) and a blocking unit (optional; not shown). For the implementation method thereof, reference may be made to the embodiments of the first aspect, and thus the detailed description thereof is omitted here.

[0059] In some embodiments, the matrix calculation unit 803 calculates a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, and also calculates an inverse multiplexing matrix for polarization demultiplexing in the Jones space based on the pilot symbol. For example, PDL compensation may be performed first, and then polarization demultiplexing may be performed. That is, first, the center of the fitting plane is moved to the origin of the Poincaré sphere to obtain the first compensation matrix, and then the fitting plane after the center is moved to the origin is rotated until its normal vector is parallel to the first axis of the Stokes space, and the fitting plane after the center is moved to the origin is rotated to the plane formed by the second axis and the third axis of the Stokes space to obtain the inverse multiplexing matrix. Specifically, reference may be made to the embodiments of the first aspect. Alternatively, polarization demultiplexing may be performed first, and then PDL compensation may be performed. That is, first, the fitting plane is rotated until its normal vector is parallel to the first axis of the Stokes space, and the fitting plane is rotated to the plane formed by the second axis and the third axis of the Stokes space to obtain the inverse multiplexing matrix, and then the center of the rotated fitting plane is moved to the origin of the Poincaré sphere to obtain the first compensation matrix. However, the detailed description thereof is omitted here.

[0060] As can be seen from the above embodiments, since the direction of the normal vector of the fitting plane can be determined using the pilot symbol, the problem that the direction of the normal vector becomes ambiguous during polarization demultiplexing can be solved, and the exchange of the two polarization states after demultiplexing is not caused.

[0061] <Embodiments of the Fourth Aspect> In an embodiment of the present invention, a polarization state tracking and recovery device is provided, and the polarization state tracking and recovery device is provided at the optical receiver end of an optical communication system. Note that the difference from the embodiment of the third aspect is that phase compensation is further performed after polarization demultiplexing.

[0062] FIG. 9 is a diagram showing a polarization state tracking and recovery device in an embodiment of the present invention. For example, the polarization state tracking and recovery device is the polarization state tracking and recovery device 100 shown in FIGS. 1A-1B. As shown in FIG. 9, the polarization state tracking and recovery device 100 includes a conversion unit 901, a fitting unit 902, a matrix calculation unit 903, a second calculation unit 905, and a recovery unit 906. The implementation manners of these units are the same as those of the conversion unit 801, the fitting unit 802, the matrix calculation unit 803, the second calculation unit 805, and the recovery unit 806 in the embodiment of the third aspect. Therefore, the repeated description is omitted here.

[0063] In some embodiments, the polarization state tracking and recovery device 100 may further include an extraction unit (optional; not shown) and a blocking unit (optional; not shown). For the implementation manner thereof, reference may be made to the embodiment of the first aspect, and the detailed description thereof is omitted here.

[0064] In some embodiments, as shown in FIG. 9, the polarization state tracking and recovery device 100 may further include the following.

[0065] A third matrix calculation unit 907: calculates a second compensation matrix for phase compensation in the Jones space; and A first calculation unit 904: calculates an SOP first rotation matrix corresponding to each pilot symbol based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix.

[0066] In some embodiments, for the implementation manners of the third matrix calculation unit 907 and the first calculation unit 904, reference may be made to the implementation manners of the third matrix calculation unit 708 and the first calculation unit 705 in the embodiment of the second aspect. Therefore, the detailed description thereof is omitted here.

[0067] As can be seen from the above embodiments, since the direction of the normal vector of the fitting plane can be determined using the pilot symbol, it is possible to solve the problem that the direction of the normal vector becomes ambiguous during polarization demultiplexing, and it is possible to prevent the exchange of the two polarization states after demultiplexing. Further, by compensating for the residual phase delay after polarization demultiplexing, the phase noise of the demultiplexed signal can also be reduced.

[0068] <Embodiment of the Fifth Aspect> In an embodiment of the present invention, a polarization state tracking and recovery device is provided, and the polarization state tracking and recovery device is provided at the optical receiver end of an optical communication system. The difference from the embodiment of the first aspect is that further phase compensation is performed after polarization demultiplexing, and the execution order of PDL compensation and polarization demultiplexing is not limited.

[0069] FIG. 10 is a diagram showing a polarization state tracking and recovery device according to an embodiment of the present invention. For example, the polarization state tracking and recovery device is the polarization state tracking and recovery device 100 shown in FIGS. 1A-1B. As shown in FIG. 10, the polarization state tracking and recovery device 100 includes the following.

[0070] Conversion unit 1001: Converts the Jones vector composed of two predetermined symbols of the two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; Fitting unit 1002: Performs fitting on the Stokes vector corresponding to each predetermined symbol on the Poincaré sphere to obtain a fitting plane; Matrix calculation unit 1003: Calculate a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, and calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space. Among them, calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and rotate the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and calculate the inverse multiplexing matrix by rotating the fitting plane to the plane composed of the second and third axes of the Stokes space; Third matrix calculation unit 1007: Calculate a second compensation matrix for phase compensation in the Jones space; First calculation unit 1004: Calculate an SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix; Second calculation unit 1005: Calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each predetermined symbol; Recovery unit 1006: Multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0071] In some embodiments, for the implementation manners of the conversion unit 1001, the fitting unit 1002, the second calculation unit 1005, and the recovery unit 1006, since the implementation manners of the conversion unit 201, the fitting unit 202, the second calculation unit 206, and the recovery unit 207 in the embodiments of the first aspect can be referred to, the detailed description thereof is omitted here.

[0072] In some embodiments, for the implementation manner of the matrix calculation unit 1003, since the implementation manner of the matrix calculation unit 803 in the embodiments of the third aspect can be referred to, the detailed description thereof is omitted here.

[0073] In some embodiments, for the implementation manners of the third matrix calculation unit 1007 and the first calculation unit 1004, reference may be made to the implementation manners of the third matrix calculation unit 708 and the first calculation unit 705 in the embodiments of the second aspect, so the detailed description thereof is omitted here.

[0074] In some embodiments, the polarization state tracking and recovery device 100 may further include an extraction unit (optional; not shown) and a blocking unit (optional; not shown). For the implementation manner thereof, reference may be made to the embodiments of the first aspect, so the detailed description thereof is omitted here.

[0075] As can be seen from the above embodiments, by compensating for the residual phase delay after polarization demultiplexing, the phase noise of the demultiplexed signal can be reduced.

[0076] <Embodiments of the Sixth Aspect> In the embodiments of the present invention, an electronic device (not shown) is further provided, and the electronic device includes the polarization state tracking and recovery device 100. Since the structure and function of the polarization state tracking and recovery device 100 are the same as those described in the embodiments of the first aspect to the fifth aspect, the detailed description thereof is omitted here.

[0077] In the embodiments of the present invention, an electronic device is further provided. FIG. 11 is a system configuration diagram of the electronic device in the embodiments of the present invention. As shown in FIG. 11, the electronic device 1100 may further include a processor 1101 and a memory 1102, and the memory 1102 is connected to the processor 1101. It should be noted that this figure is only an example, and other types of structures may be used to supplement or replace this structure to realize the electrical communication function or other functions.

[0078] As shown in FIG. 11, the electronic device 1100 may further include an input unit 1103, a display 1104, a power supply 1105, etc.

[0079] In some embodiments, the function of the polarization state tracking and recovery device on the first side may be integrated into the processor 1101. Among them, the processor 1101 may be configured as follows, that is, convert the Jones vector composed of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector for a predetermined symbol; perform fitting on the Poincaré sphere for the Stokes vector corresponding to each said predetermined symbol to obtain a fitting plane; calculate a first compensation matrix for polarization-dependent loss PDL compensation in the Jones space, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere; calculate a demultiplexing matrix for polarization demultiplexing in the Jones space, wherein the fitting plane after moving the center to the origin is rotated until its normal vector is parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane composed of the second axis and the third axis of the Stokes space to calculate the demultiplexing matrix; calculate an SOP first rotation matrix corresponding to each said predetermined symbol based on the first compensation matrix and the demultiplexing matrix; calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each said predetermined symbol; and multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0080] In some embodiments, the function of the polarization state tracking and recovery device on the second side may be integrated into the processor 1101. Among them, the processor 1101 may be configured as follows, that is, convert the Jones vector composed of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; perform fitting on the Stokes vector corresponding to each of the predetermined symbols on the Poincaré sphere to obtain a fitting plane; calculate a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, and calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere; calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space, and calculate the inverse multiplexing matrix by rotating the fitting plane after moving the center to the origin until its normal vector is parallel to the first axis of the Stokes space, and rotating the fitting plane after moving the center to the origin to the plane composed of the second axis and the third axis of the Stokes space; calculate a second compensation matrix for phase compensation in the Jones space; calculate an SOP first rotation matrix corresponding to each of the predetermined symbols based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix; calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each of the predetermined symbols; multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0081] In some embodiments, the function of the polarization state tracking and recovery device on the third side may be integrated into the processor 1101. Among them, the processor 1101 may be configured as follows, that is, convert the Jones vector composed of the pilot symbols of the two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; perform fitting on the Poincaré sphere for the Stokes vector corresponding to each pilot symbol to obtain a fitting plane; calculate a first compensation matrix for polarization-dependent loss PDL compensation in the Jones space, and also calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space based on the pilot symbol, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere, and the inverse multiplexing matrix is calculated by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and rotating the fitting plane to the plane composed of the second axis and the third axis of the Stokes space; calculate an SOP first rotation matrix corresponding to each pilot symbol based on the first compensation matrix and the inverse multiplexing matrix; calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each pilot symbol; and multiply the two-dimensional vector composed of the two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0082] In some embodiments, the function of the polarization state tracking and recovery device on the fourth side surface may be integrated into the processor 1101. Among them, the processor 1101 may be configured as follows, that is, convert the Jones vector composed of pilot symbols of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; perform fitting on the Poincaré sphere for the Stokes vector corresponding to each pilot symbol to obtain a fitting plane; calculate a first compensation matrix for polarization-dependent loss PDL compensation in the Jones space, and also calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space based on the pilot symbol. Among them, calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and calculate the inverse multiplexing matrix by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and rotating the fitting plane to the plane composed of the second axis and the third axis of the Stokes space; calculate a second compensation matrix for phase compensation in the Jones space; calculate an SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix; calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each pilot symbol; and multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0083] In some embodiments, the function of the polarization state tracking and recovery device on the fifth side surface may be integrated into the processor 1101. Among them, the processor 1101 may be configured as follows, that is, convert the Jones vector composed of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector for a predetermined symbol; perform fitting on the Poincaré sphere for the Stokes vector corresponding to each said predetermined symbol to obtain a fitting plane; calculate a first compensation matrix for polarization-dependent loss PDL compensation in the Jones space, and calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space. Among them, calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and calculate the inverse multiplexing matrix by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and rotating the fitting plane to the plane composed of the second axis and the third axis of the Stokes space; calculate a second compensation matrix for phase compensation in the Jones space; calculate an SOP first rotation matrix corresponding to each said predetermined symbol based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix; calculate the SOP first rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each said predetermined symbol; and multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0084] In another embodiment, the polarization state tracking and recovery device described on the first to fifth side surfaces may be separately arranged from the processor 1101. For example, the polarization state tracking and recovery device may be configured as a chip connected to the processor 1101, and the function of the polarization state tracking and recovery device may be realized under the control of the processor 1101.

[0085] It should be noted that in this embodiment, the electronic device 1100 does not necessarily include all the components in FIG. 11.

[0086] Also, as shown in FIG. 11, the processor 1101 may be referred to as a controller or an operation controller, and may include a microprocessor or other processing device and / or logic device. The processor 1101 can receive an input and control the operation of each component of the electronic device 1100.

[0087] The memory 1102 may include, for example, one or more of a buffer, flash memory, HDD, removable medium, volatile memory, non-volatile memory, or other suitable devices. Also, the processor 1101 can execute the program stored in the memory 1102 to perform information storage or processing, etc. Since the functions of other components are similar to those of the prior art, detailed descriptions thereof are omitted here. Further, each component of the electronic device 1100 may be realized by dedicated hardware, firmware, software, or a combination thereof, and all of them belong to the scope of the present invention.

[0088] In this embodiment, the electronic device 1100 may be independent. For example, it may be an independent computer, or may be integrated into an optical receiver.

[0089] As can be seen from the above embodiments, by rotating the fitting plane after moving the center to the origin until the normal vector thereof is parallel to the first axis of the Stokes space, and rotating the fitting plane after moving the center to the origin to the plane formed by the second axis and the third axis of the Stokes space, an inverse multiplexing matrix for polarization demultiplexing is calculated. That is, in order to perform PDL compensation before polarization demultiplexing, the computational complexity can be reduced. Also, since the direction of the normal vector of the fitting plane can be determined using a pilot symbol, problems such as ambiguity in the direction of the normal vector during polarization demultiplexing can be solved, and exchange of the two polarization states after demultiplexing will not be caused. Further, by compensating for the residual phase delay after polarization demultiplexing, the phase noise of the demultiplexed signal can be reduced.

[0090] <Embodiment of the seventh aspect> In an embodiment of the present invention, a polarization state tracking and recovery method is further provided, which corresponds to the polarization state tracking and recovery devices on the first to fifth sides.

[0091] FIG. 12 is a diagram showing the polarization state tracking and recovery method in an embodiment of the present invention. As shown in FIG. 12 corresponding to the embodiments of the first side and the second side, the method includes the following steps.

[0092] 1201: Convert the Jones vector composed of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector from a predetermined symbol; 1202: Perform fitting on the Stokes vector corresponding to each predetermined symbol on the Poincaré sphere to obtain a fitting plane; 1203: Calculate a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere; 1204: Calculate a conversion matrix for polarization de-multiplexing in the Jones space, wherein the fitting plane after moving the center to the origin is rotated until its normal vector is parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane composed of the second axis and the third axis of the Stokes space to calculate the de-multiplexing matrix; 1205: Calculate an SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix and the de-multiplexing matrix; 1206: Calculate the SOP first rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each predetermined symbol; 1207: Multiply the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix to recover the optical reception signals of the two polarization states in the optical reception signal.

[0093] In some embodiments, the method may further include the following (not shown), that is, after 1204, calculate a second compensation matrix for phase compensation in the Jones space. For the calculation method of the second compensation matrix, reference can be made to the embodiments of the second aspect, so the detailed description thereof is omitted here. Also, at 1205, based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix, calculate an SOP first rotation matrix corresponding to each predetermined symbol.

[0094] FIG. 13 is a diagram showing a polarization state tracking and recovery method according to an embodiment of the present invention. As shown in FIG. 13 corresponding to the embodiments of the third aspect and the fourth aspect, the method includes the following steps.

[0095] 1301: Convert the Jones vector composed of pilot symbols of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; 1302: Perform fitting on the Stokes vector corresponding to each pilot symbol on the Poincaré sphere to obtain a fitting plane; 1303: Calculate a first compensation matrix for polarization-dependent loss (PDL) compensation in the Jones space, and calculate a demultiplexing matrix for polarization demultiplexing in the Jones space based on the pilot symbols. Among them, calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and rotate the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and calculate the demultiplexing matrix by rotating the fitting plane to the plane composed of the second axis and the third axis of the Stokes space; 1304: Calculate an SOP first rotation matrix corresponding to each pilot symbol based on the first compensation matrix and the demultiplexing matrix; 1305: Calculate an SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each pilot symbol; 1306: By multiplying the two-dimensional vector consisting of two polarization states in the optical reception signal by the SOP second rotation matrix, the optical reception signals of the two polarization states in the optical reception signal are recovered.

[0096] In some embodiments, the method may further include the following (not shown), that is, after 1303, a second compensation matrix for phase compensation in the Jones space is calculated. For the calculation method of the second compensation matrix, reference can be made to the embodiments of the second aspect, so the detailed description thereof is omitted here. Also, in 1304, an SOP first rotation matrix corresponding to each pilot symbol is calculated based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix.

[0097] FIG. 14 is a diagram showing a polarization state tracking and recovery method according to an embodiment of the present invention. As shown in FIG. 14 corresponding to the embodiment of the fifth aspect, the method includes the following steps.

[0098] 1401: Convert the Jones vector consisting of two predetermined symbols of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; 1402: Perform fitting on the Stokes vector corresponding to each predetermined symbol on the Poincaré sphere to obtain a fitting plane; 1403: Calculate a first compensation matrix for polarization-dependent loss compensation in the Jones space, and also calculate a demultiplexing matrix for polarization demultiplexing in the Jones space. Among them, the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere, and the inverse multiplexing matrix is calculated by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and rotating the fitting plane to the plane consisting of the second and third axes of the Stokes space; 1404: Calculate a second compensation matrix for phase compensation in the Jones space; 1405: Calculate an SOP first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix; 1406: Calculate the SOP second rotation matrix at different times of the optical reception signal based on the SOP first rotation matrix corresponding to each of the predetermined symbols; 1407: By multiplying the two-dimensional vector composed of two polarization states in the optical reception signal by the SOP second rotation matrix, the optical reception signals of the two polarization states in the optical reception signal are recovered.

[0099] FIGS. 15-16 are diagrams showing a polarization state tracking and recovery method in an embodiment of the present invention. As shown in FIGS. 15-16, the method includes the following steps.

[0100] 1601: Extract predetermined symbols of two polarization states from the dual-polarization multiplexed optical reception signal; 1602: Based on the predetermined symbol, the rotation matrix R n in the Jones space of the polarization state corresponding to the predetermined symbol is calculated; 1603: Calculate the rotation matrix R m at different times of the optical reception signal by an interpolation algorithm; 1604: By multiplying the two-dimensional vector composed of two polarization states in the optical reception signal by the R m the optical reception signals of the two polarization states in the optical reception signal are recovered.

[0101] FIG. 17 is a diagram showing a method for calculating the rotation matrix corresponding to a predetermined symbol in operation 1602. As shown in FIG. 17, operation 1602 includes the following steps.

[0102] 1701: Convert the Jones vector composed of predetermined symbols of two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; 1702: Perform fitting on the Stokes vector corresponding to each of the predetermined symbols on the Poincare sphere to obtain a fitting plane; 1703: Calculate a first compensation matrix for polarization-dependent loss (PDL) compensation in Jones space, and calculate a demultiplexing matrix for polarization demultiplexing in Jones space, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincare sphere, and the demultiplexing matrix is calculated by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and by rotating the fitting plane to the plane formed by the second and third axes of the Stokes space; 1704 (optional): Calculate a second compensation matrix for phase compensation in Jones space; 1705: Calculate an SOP first rotation matrix corresponding to each of the predetermined symbols based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix (the second compensation matrix is optional).

[0103] In this embodiment, for the execution of each of the above operations, reference can be made to the realization of the functions of each component in the embodiments of the first to fifth aspects, and thus redundant descriptions are omitted here.

[0104] It should be noted that the above FIGS. 12 - 17 are only illustrative of the embodiments of the present invention, and the present invention is not limited thereto. For example, the execution order between each operation can be appropriately adjusted, or several steps can be increased or decreased. That is, those skilled in the art can appropriately modify the above content based on the descriptions of FIGS. 12 - 17 above.

[0105] Each of the above embodiments is illustrative of the embodiments of the present invention, but the present invention is not limited thereto, and further appropriate modifications can be made based on each of the above embodiments. For example, each of the above embodiments can be used alone, or one or more of the above embodiments can be combined and used.

[0106] As can be seen from the above embodiments, the fitting plane after moving the center to the origin is rotated until its normal vector becomes parallel to the first axis of the Stokes space, and the fitting plane after moving the center to the origin is rotated to the plane composed of the second axis and the third axis of the Stokes space, thereby calculating the demultiplexing matrix for polarization demultiplexing. That is, in order to perform PDL compensation before polarization demultiplexing, the computational complexity can be reduced. In addition, since the direction of the normal vector of the fitting plane can be determined using the pilot symbol, the problem that the direction of the normal vector becomes ambiguous during polarization demultiplexing can be solved, and the exchange of the two polarization states after demultiplexing will not be caused. Furthermore, by compensating for the residual phase delay after polarization demultiplexing, the phase noise of the demultiplexed signal can be reduced.

[0107] In an embodiment of the present invention, a computer-readable program is further provided. When the program is executed in the polarization state tracking and recovery device or the electronic device, the program causes the computer to execute the polarization state tracking and recovery method described in the embodiment of the seventh aspect in the polarization state tracking and recovery device or the electronic device.

[0108] In an embodiment of the present invention, a storage medium storing a computer-readable program is further provided. The computer-readable program causes the computer to execute the polarization state tracking and recovery method described in the seventh aspect in the polarization state tracking and recovery device or the electronic device.

[0109] In addition, the methods, apparatuses, etc. described in the embodiments of the present invention can be implemented by hardware, software modules executed by a processor, or a combination of both. For example, one or more functions in the functional block diagram and / or a combination of one or more functions in the functional block diagram may correspond to each software module in the computer program or to each hardware module. Also, these software modules can each correspond to each step shown in the diagram showing the method. These hardware modules can be realized, for example, by solidifying these software modules using an FPGA (field-programmable gate array).

[0110] In addition, the apparatuses, methods, etc. according to the embodiments of the present invention may be implemented by software, may be implemented by hardware, or may be implemented by a combination of hardware and software. The present invention also relates to such a computer-readable program, that is, when the program is executed by a logic component, the logic component can realize the above-described apparatus or component, or the logic component can realize the above-described method or its steps. Furthermore, the present invention also relates to a storage medium storing the above-described program, such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, etc.

[0111] In addition, regarding the above embodiments, etc., the following supplementary notes are further disclosed.

[0112] (Supplementary Note 1) A polarization state tracking and recovery method, comprising: converting a Jones vector composed of predetermined symbols of two polarization states in a dual-polarization multiplexed optical reception signal into a Stokes vector; performing fitting on the Stokes vector corresponding to each of the predetermined symbols on a Poincaré sphere to obtain a fitting plane; Calculate a first compensation matrix for polarization-dependent loss compensation in Jones space, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere; Calculate a demultiplexing matrix for polarization demultiplexing in Jones space, wherein the demultiplexing matrix is calculated by rotating the fitting plane after moving the center to the origin until its normal vector is parallel to the first axis of the Stokes space, and by rotating the fitting plane after moving the center to the origin to the plane formed by the second and third axes of the Stokes space; Calculate a first rotation matrix of the polarization state corresponding to each of the predetermined symbols based on the first compensation matrix and the demultiplexing matrix; Calculate a second rotation matrix of the polarization state at different times of the optical reception signal based on the first rotation matrix of the polarization state corresponding to each of the predetermined symbols; and A method including multiplying the second rotation matrix of the polarization state by a two-dimensional vector composed of two polarization states in the optical reception signal to recover the optical reception signals of the two polarization states in the optical reception signal.

[0113] (Appendix 2) The method according to Appendix 1, wherein The predetermined symbol is a QPSK pilot symbol.

[0114] (Appendix 3) The method according to Appendix 2, further comprising Extracting predetermined symbols of two polarization states from the dual-polarization multiplexed optical reception signal; Performing block division on the pilot symbols, each block including a first predetermined number of predetermined symbols; and Fitting on the Poincaré sphere for the Stokes vectors corresponding to all the predetermined symbols in each block with each block as a unit to obtain the fitting plane corresponding to each block.

[0115] (Appendix 4) The method according to Appendix 3, wherein Obtaining a fitting plane includes: performing grouping on the QPSK pilot symbols in each block based on the positions of the QPSK pilot symbols in each block on the Poincare sphere; calculating the average value of each group to obtain a center point; and performing fitting on the center points of each group to obtain the fitting plane.

[0116] (Appendix 5) The method according to Appendix 4, wherein calculating the demultiplexing matrix includes calculating a normal vector of the fitting plane based on the center points of each group, calculating an included angle between the normal vector and the first axis, determining a rotation axis for rotating the first axis vector to the normal vector, and calculating the demultiplexing matrix based on the included angle and the rotation axis.

[0117] (Appendix 6) The method according to Appendix 5, wherein calculating the normal vector includes performing a cross multiplication of vectors from the origin of the Poincare sphere to at least one pair of adjacent center points, and determining the normal vector based on the result of the cross multiplication of at least one pair of vectors, wherein the order of the cross multiplication of at least one pair of adjacent two center points is determined according to the counterclockwise order on the plane formed by the second axis and the third axis of the reference point, the reference point includes (0, 1, 0), (0, 0, 1), (0, -1, 0), (0, 0, -1).

[0118] (Appendix 7) The method according to Appendix 4, further including calculating a second compensation matrix for phase compensation in the Jones space, by the transformation of the phase compensation, continuously rotating the fitting plane rotated to the plane formed by the second axis and the third axis until the center points of each group overlap with their respective reference points. The reference points include (0, 1, 0), (0, 0, 1), (0, -1, 0), and (0, 0, -1), A method for calculating a first rotation matrix of a polarization state corresponding to each predetermined symbol based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix.

[0119] (Appendix 8) The method according to Appendix 7, wherein the calculation of the second compensation matrix includes determining a rotation angle based on an included angle between the center point of each group and the reference point, and calculating the second compensation matrix for the phase compensation based on the rotation angle and the rotation axis, wherein the rotation axis is the first axis.

[0120] (Appendix 9) The method according to Appendix 3, wherein the first predetermined quantity N of pilot symbols included in the nth block includes those from the (n - ((N - 1) / 2))th pilot symbol to the (n + ((N - 1) / 2))th pilot symbol.

[0121] (Appendix 10) The method according to Appendix 4, Performing grouping includes determining a reference point corresponding to each pilot symbol, and grouping pilot symbols with the same reference point into one group, wherein the reference points include (0, 1, 0), (0, 0, 1), (0, -1, 0), and (0, 0, -1).

[0122] (Appendix 11) The method according to Appendix 8, wherein the calculation of the rotation axis includes performing a cross multiplication of the first axis vector and the normal vector, and determining the result of the normalization as the rotation axis.

[0123] (Appendix 12) The method according to Appendix 2, Calculating the polarization state second rotation matrix at different times of the optical reception signal based on the polarization state first rotation matrix corresponding to each predetermined symbol includes calculating the polarization state third rotation matrix corresponding to the non-pilot symbol in the optical reception signal by an interpolation algorithm; and constructing the polarization state second rotation matrix by combining the polarization state first rotation matrix and the polarization state third rotation matrix.

[0124] (Appendix 13) A polarization state tracking and recovery method, Converting the Jones vector composed of the pilot symbols of the two polarization states in the dual-polarization multiplexed optical reception signal into a Stokes vector; Performing fitting on the Stokes vector corresponding to each of the pilot symbols on the Poincaré sphere to obtain a fitting plane; Calculating a first compensation matrix for polarization-dependent loss compensation in the Jones space, and calculating an inverse multiplexing matrix for polarization demultiplexing in the Jones space based on the pilot symbols, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere, and the inverse multiplexing matrix is calculated by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and rotating the fitting plane to the plane composed of the second axis and the third axis of the Stokes space; Calculating a polarization state first rotation matrix corresponding to each of the pilot symbols based on the first compensation matrix and the inverse multiplexing matrix; Calculating a polarization state second rotation matrix at different times of the optical reception signal based on the polarization state first rotation matrix corresponding to each of the pilot symbols; and Restoring the optical reception signals of the two polarization states in the optical reception signal by multiplying the two-dimensional vector composed of the two polarization states in the optical reception signal by the polarization state second rotation matrix.

[0125] (Appendix 14) A polarization state tracking and recovery method, Convert the Jones vector consisting of two predetermined symbols in a dual-polarization multiplexed optical reception signal into a Stokes vector; Perform fitting on the Poincaré sphere for the Stokes vector corresponding to each of the predetermined symbols to obtain a fitting plane; Calculate a first compensation matrix in the Jones space for polarization-dependent loss compensation in the Jones space, and also calculate an inverse multiplexing matrix for polarization demultiplexing in the Jones space. Among them, calculate the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere, and rotate the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and rotate the fitting plane to the plane composed of the second axis and the third axis of the Stokes space to calculate the inverse multiplexing matrix; Calculate a second compensation matrix for phase compensation in the Jones space; Calculate a polarization state first rotation matrix corresponding to each of the predetermined symbols based on the first compensation matrix, the inverse multiplexing matrix, and the second compensation matrix; Calculate a polarization state second rotation matrix at different times of the optical reception signal based on the polarization state first rotation matrix corresponding to each of the predetermined symbols; and A method including recovering the optical reception signals of two polarization states in the optical reception signal by multiplying the two-dimensional vector consisting of two polarization states in the optical reception signal by the polarization state second rotation matrix.

[0126] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to this embodiment. Without departing from the spirit of the present invention, any changes to the present invention belong to the technical scope of the present invention.

Claims

1. A polarization state tracking and recovery device, comprising: a conversion unit that converts a Jones vector composed of two polarization states in a dual-polarization multiplexed optical reception signal into a Stokes vector; a fitting unit that performs fitting on the Stokes vector corresponding to each of the predetermined symbols on the Poincaré sphere to obtain a fitting plane; a first matrix calculation unit that calculates a first compensation matrix for polarization-dependent loss compensation in the Jones space, and calculates the first compensation matrix by moving the center of the fitting plane to the origin of the Poincaré sphere; a second matrix calculation unit that calculates a demultiplexing matrix for polarization demultiplexing in the Jones space, and calculates the demultiplexing matrix by rotating the fitting plane after moving the center to the origin until the normal vector thereof is parallel to the first axis of the Stokes space, and rotating the fitting plane after moving the center to the origin to a plane composed of the second axis and the third axis of the Stokes space; a first calculation unit that calculates a first rotation matrix of the polarization state corresponding to each of the predetermined symbols based on the first compensation matrix and the demultiplexing matrix; a second calculation unit that calculates a second rotation matrix of the polarization state (SOP) at different times of the optical reception signal based on the first rotation matrix of the polarization state (SOP) corresponding to each of the predetermined symbols; and a recovery unit that multiplies a two-dimensional vector composed of two polarization states in the optical reception signal by the second rotation matrix of the polarization state to recover the optical reception signals of the two polarization states in the optical reception signal.

2. The device according to claim 1, wherein the predetermined symbol is a QPSK pilot symbol.

3. The device according to claim 2, further comprising: an extraction unit that extracts predetermined symbols of two polarization states from the dual-polarization multiplexed optical reception signal; and a block division unit that performs block division on the pilot symbols, each block including a first predetermined number of the predetermined symbols, wherein the fitting unit performs fitting on the Stokes vectors corresponding to all the predetermined symbols in each block on the Poincaré sphere in units of each block to obtain the fitting plane corresponding to each block.

4. The device according to claim 3, wherein The fitting unit is a sorting module that sorts the QPSK pilot symbols in each block based on the positions of the QPSK pilot symbols in each block on the Poincaré sphere; a calculation module that calculates the average value of each group to obtain a center point; and a fitting module that performs fitting on the center point of each group to obtain the fitting plane, the device comprising.

5. The device according to claim 4, wherein the second matrix calculation unit calculates a normal vector of the fitting plane based on the center point of each group, calculates an included angle between the normal vector and the first axis, determines a rotation axis for rotating the first axis vector to the normal vector, and calculates the demultiplexing matrix based on the included angle and the rotation axis, the device.

6. The device according to claim 5, wherein the second matrix calculation unit performs a cross multiplication of vectors from the origin of the Poincaré sphere to at least one pair of adjacent center points, determines the normal vector based on the result of the cross multiplication of at least one pair of vectors, the order of the cross multiplication of at least one pair of adjacent two center points is determined according to the counterclockwise order on the plane composed of the second axis and the third axis of the reference point, the reference point includes (0, 1, 0), (0, 0, 1), (0, -1, 0), and (0, 0, -1), the device.

7. The device according to claim 4, further comprising a third matrix calculation unit that calculates a second compensation matrix for phase compensation in the Jones space, wherein the third matrix calculation unit calculates the second compensation matrix by continuously rotating the fitting plane rotated to the plane composed of the second axis and the third axis until the center point of each group overlaps with its reference point, the reference point includes (0, 1, 0), (0, 0, 1), (0, -1, 0), and (0, 0, -1), the first calculation unit calculates a polarization state first rotation matrix corresponding to each predetermined symbol based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix, the device.

8. The device according to claim 7, wherein the third matrix calculation unit determines a rotation angle based on the included angle between the center point and the reference point of each group, and calculates the second compensation matrix based on the rotation angle and the rotation axis, the rotation axis is the first axis, the device.

9. The device according to claim 3, The apparatus, wherein the first predetermined number (N) of pilot symbols included in the n-th block includes pilot symbols from the (n - ((N - 1) / 2))-th pilot symbol to the (n + ((N - 1) / 2))-th pilot symbol.

10. The apparatus according to claim 4, wherein the grouping module determines a reference point corresponding to each pilot symbol, and groups pilot symbols having the same reference point into one set; the apparatus, wherein the reference points include (0, 1, 0), (0, 0, 1), (0, -1, 0), and (0, 0, -1).

11. The apparatus according to claim 8, wherein the third matrix calculation unit performs a cross multiplication of the vector of the first axis and the normal vector, and determines the result of the normalization as the rotation axis.

12. The apparatus according to claim 2, wherein the second calculation unit calculates a third rotation matrix of the polarization state corresponding to the non-pilot symbol in the optical reception signal by an interpolation algorithm; and the apparatus, wherein the second rotation matrix of the polarization state is configured by combining the first rotation matrix of the polarization state and the third rotation matrix of the polarization state.

13. A polarization state tracking and recovery apparatus, a conversion unit that converts a Jones vector composed of pilot symbols of two polarization states in a dual-polarization multiplexed optical reception signal into a Stokes vector; a fitting unit that performs fitting on the Stokes vector corresponding to each of the pilot symbols on a Poincaré sphere to obtain a fitting plane; a matrix calculation unit that calculates a first compensation matrix for polarization-dependent loss compensation in Jones space, and also calculates a demultiplexing matrix for polarization demultiplexing in Jones space based on the pilot symbols, wherein the first compensation matrix is calculated by moving the center of the fitting plane to the origin of the Poincaré sphere, and the demultiplexing matrix is calculated by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space, and rotating the fitting plane to a plane composed of the second axis and the third axis of the Stokes space; a first calculation unit that calculates a first rotation matrix of the polarization state corresponding to each of the pilot symbols based on the first compensation matrix and the demultiplexing matrix; A second calculation unit that calculates a second rotation matrix of the polarization state at different times of the optical reception signal based on the polarization state first rotation matrix corresponding to each of the pilot symbols; and An apparatus including a recovery unit that recovers the optical reception signals of the two polarization states in the optical reception signal by multiplying a two-dimensional vector composed of the two polarization states in the optical reception signal by the second rotation matrix of the polarization state.

14. A polarization state tracking and recovery apparatus, comprising A conversion unit that converts a Jones vector composed of predetermined symbols of two polarization states in a dual-polarization multiplexed optical reception signal into a Stokes vector; A fitting unit that performs fitting on the Stokes vector corresponding to each of the predetermined symbols on a Poincare sphere to obtain a fitting plane; A matrix calculation unit that calculates a first compensation matrix in the Jones space for polarization-dependent loss compensation in the Jones space and also calculates a demultiplexing matrix for polarization demultiplexing in the Jones space, the matrix calculation unit calculating the first compensation matrix by moving the center of the fitting plane to the origin of the Poincare sphere, and calculating the demultiplexing matrix by rotating the fitting plane until its normal vector is parallel to the first axis of the Stokes space and rotating the fitting plane to a plane composed of the second axis and the third axis of the Stokes space; A third matrix calculation unit that calculates a second compensation matrix for phase compensation in the Jones space; A first calculation unit that calculates a first rotation matrix of the polarization state corresponding to each of the predetermined symbols based on the first compensation matrix, the demultiplexing matrix, and the second compensation matrix; A second calculation unit that calculates a second rotation matrix of the polarization state at different times of the optical reception signal based on the first rotation matrix of the polarization state corresponding to each of the predetermined symbols; and An apparatus including a recovery unit that recovers the optical reception signals of the two polarization states in the optical reception signal by multiplying a two-dimensional vector composed of the two polarization states in the optical reception signal by the second rotation matrix of the polarization state (SOP).

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