WO2023249509A1 - Procédé de commande de polarisation et dispositif associé - Google Patents

Procédé de commande de polarisation et dispositif associé Download PDF

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Publication number
WO2023249509A1
WO2023249509A1 PCT/RU2022/000197 RU2022000197W WO2023249509A1 WO 2023249509 A1 WO2023249509 A1 WO 2023249509A1 RU 2022000197 W RU2022000197 W RU 2022000197W WO 2023249509 A1 WO2023249509 A1 WO 2023249509A1
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WIPO (PCT)
Prior art keywords
optical signal
parameters
signal
control
state
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Application number
PCT/RU2022/000197
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English (en)
Inventor
Alexander Mikhaylovich LEBEDEV
Dmitry Anatolievich DOLGIKH
Wanyang WU
Tao Gui
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Huawei Technologies Co., Ltd
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Priority to PCT/RU2022/000197 priority Critical patent/WO2023249509A1/fr
Publication of WO2023249509A1 publication Critical patent/WO2023249509A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/615—Arrangements affecting the optical part of the receiver
    • H04B10/6151—Arrangements affecting the optical part of the receiver comprising a polarization controller at the receiver's input stage

Definitions

  • Embodiments of the present invention relate to the field of optical accesses and transport networks, and more specifically, to a method for polarization control and a related device.
  • a coherent optical detection is one of the essential techniques in modem high-speed optical fiber communications systems enabling the use of multiple degrees of freedom for data modulation, i.e., 1) amplitude and phase of the signal (or quadratures), and 2) X/Y orthogonal polarizations of the optical signal i.e., so-called polarization multiplexing (PolMUX) technique.
  • PolMUX polarization multiplexing
  • Embodiments of this application provide a method for polarization control and a related device. According to the technical solution, enabling enhances optical transmission system resilience against random dynamic polarization rotation.
  • an embodiment of this application provides a method for polarization control.
  • the method includes: separating an input optical signal into a first optical signal and a second optical signal; obtaining a third and fourth optical signals by phase shifting and coupling of the optical signals according to control parameters, where the control parameters are obtained by cyclic adaptation of Kalman filter algorithm; obtaining an output optical signal by combining the third optical signal and the fourth optical signal.
  • the method further includes: obtaining a monitoring signal by sampling the first optical signal and the second optical signa! at a PC core (PCC) output; and calculating the monitoring signal to obtain control parameters by cyclic adaptation of Kalman filter algorithm.
  • PCC PC core
  • basic control parameters include N basic parameters, N> 1, where the method further includes: adding an additional value to the first parameter of the N basic parameters to obtain first estimated parameters ; and obtaining numerical derivatives of a first Stokes component SI i and a second Stokes component S2i corresponding to the first estimated parameters. And the method further includes: adding the additional value to the Nth parameter of the N basic parameters to obtain Nth estimated parameters; obtaining numerical derivatives of a first Stokes component S 1N and a second Stokes component S2N corresponding to the Nth estimated parameters.
  • multiple sources of information are used in the algorithm (e.g. 2 components of Stokes vector can be used for adaptation) overcoming the limitations of conventional scalar gradient descent, GD, loss function based approaches for polarization controller adaptation cause Kalman algorithmic procedure is a natural match for the multi-objective polarization control task, i.e., tracking that uses SI and S2 Stokes vector components instead of using only SI.
  • no sinusoidal dither needs to be generated, and the dithering is performed by a rectangular pulse allowing to find the numerical derivatives.
  • the method further includes: storing a value of the numerical derivatives in the corresponding column of the Jacobi Matrix, where the value of the numerical derivatives corresponds to the first estimated parameters to the Nth estimated parameters.
  • P k P k -K k HP k (7) ;
  • the Kalman correction includes the equation (5), equation (6) and equation (7), where x is the estimated state, z is a target state in the Stokes domain, A is a measured state in Stokes domain, P is a state error covariance, A is a transition matrix (set as an identity matrix in the RSOP control case), H is a Jacobi matrix, Q and R are the process and measurement noise covariance matrices respectively, K is the Kalman gain, a is a leakage coefficient, apriori state and error covariance are written as x “and P k ⁇ , aposteriori state and error covariance are written as x* and P k , k is the iteration number.
  • the algorithm achieves high-speed (e.g. 100 kRad/s) reset-free polarization tracking and equalization in the optical domain, and causes multiplication of the state vector by the leakage coefficient leads to the parameters (phases or voltages) constraining to a limited range allowing to achieve the optimum in terms of the tracking speed.
  • an embodiment of this application provides a device (100) for polarization control, characterized in including: a first polarization splitter-rotator, PSR (101), configured to separate an input optical signal into a first optical signal and a second optical signal; a polarization controller core, PCC (103), configured to obtain a third and fourth optical signals (2 outputs of the PCC) by phase shifting and coupling of the optical signals according to control parameters, where the control parameters are obtained by cyclic adaptation of Kalman filter algorithm based on basic control parameters; a second PSR (102), configured to obtain an output optical signal by combining the third optical signal and the fourth optical signal.
  • the polarization controller core further includes: N phase shifters, PS(e.g. PS 1, PS 2, PS 3, PS 4), configured to obtain the third optical signal by phase shifting the first optical signal according to the control parameters, N > 1 ; M photodiodes, PD(e.g. PD 1, PD 2, PD 3, PD 4), configured to obtain a first electrical signal and a second electrical signal by converting the first optical signal and the second optical signal, M> 1; M analog-to-digital (A/D) converters (e.g.
  • A/D 1, A/D 2, A/D 3, A/D 4 configured to obtain a first digital signal and a second digital signal by converting the first electrical signal and the second electrical signal, and obtaining a monitoring signal by sampling the first digital signal and the second digital signal, M> 1 ;
  • a processor configured to obtain a control signal by cyclic adaptation of Kalman filter algorithm based on the monitoring signal;
  • M digital-to-analog (D/A) converters e.g. D/A 1, D/A 2, D/A 3, D/A 4
  • an amplifier, AM configured to amplify the control parameters.
  • the number N of phase shifters may be 4 or less. And using 4 phase shifters also contributes to the reduction of the required range of control signal values (as compared to the 3 or less phase shifters solution) allowing to achieve the optimum in terms of the tracking speed and the required control signal range applied to phase shifters.
  • the basic control parameters include N basic parameters, N> 1
  • the processor is further configured to add an additional value to the first parameter of the N basic parameters to obtain first estimated parameters, and obtain numerical derivatives of a first Stokes component Sli and a second Stokes component S2i corresponding to the first estimated parameters.
  • the processor is further configured to add the additional value to the Nth parameter of the N basic parameters to obtain Nth estimated parameters, and obtain numerical derivatives of a first Stokes component S 1N and a second Stokes component S2N corresponding to the Nth estimated parameters.
  • the processor is further configured to store a value of the numerical derivatives in the corresponding column of the Jacobi Matrix, where the value of the numerical derivatives corresponds to the first estimated parameters to the Nth estimated parameters.
  • the Kalman prediction includes the equation (3) and equation (4)
  • the Kalman correction includes the equation (5), equation (6) and equation (7), where x is the estimated state, z is a target state in the Stokes domain, h is a measured state in Stokes domain, P is a state error covariance, A is a transition matrix (set as an identity matrix in the RSOP control case), H is a Jacobi matrix, Q and R are the process and measurement noise covariance matrices respectively, K is the Kalman gain, a is a leakage coefficient, apriori state and error covariance are written as x t ⁇ and P k , aposteriori state and error covariance are written as x and P k , k is the iteration number.
  • an embodiment of this application provides a computer readable storage medium, including instructions.
  • the instructions runs on a computer, the computer is enabled to perform the method in the first aspect or any possible implementation of the first aspect.
  • a computer program product is provided, where when the computer program product runs on a computer, the computer is enabled to perform the method in the first aspect or any possible implementation of the first aspect.
  • FIG.1 shows an overall polarization controller (PC) scheme including PSR before and after the controller.
  • PC polarization controller
  • FIG. 2 shows the polarization controller block diagram.
  • FIG. 3 shows the adaptation cycle including the calculation of numerical derivatives and Jacobi matrix, and Kalman adaptation.
  • FIG. 4 shows a method for polarization control.
  • FIG. 5 shows an application scenario. DESCRIPTION OF EMBODIMENTS
  • FIG. 1 illustrates exemplarily an optical hardware structure of this disclosure. It includes a polarization controller core (PCC) and 2 polarization splitter-rotators (PSR). The focus of our design is on the polarization controller core (PCC) block.
  • PCC polarization controller core
  • a particular designed combination of hardware components (the number of phase shifters - four, couplers - four, photodiodes -four) and the proposed control method/algorithm allow to achieve an advantage in terms of reducing the range for control voltages and increasing the tracking speed.
  • the hardware scheme in FIG. 1 includes PSR consisting of Polarization beam splitter (PBS) and the constant 90 degrees rotation section.
  • PBS separates TE and TM polarization modes into different waveguides, and then one of the outputs is rotated by 90 degrees.
  • Analogous post-processing operation is performed after PCC with the second PSR.
  • FIG. 2 shows the chosen hardware implementation of the overall PC, including the electrical and adaptive computation part.
  • the PCC consists of variable phase shifters (PS1-PS4) and fixed 2x2 3dB optical couplers (C1-C4). Monitor the signal that is provided by tapping the optical power to 4 photodiodes (PD) and then sample the signal by analog-to-digital (A/D) converters. Based on the following computation using our proposed modified Kalman filter method, a constantly updating set of control parameters is applied to phase shifters via digital to analog (D/A) conversion and amplification.
  • the hardware scheme in FIG. 2 is suitable for detecting SI, S2 or only S I and can be extended to include S3 detection. For example, four (4) photodiodes are used for detection of the feedback signal for S1+S2 adaptation.
  • the Kalman filter is a very good match for the detection solution which enables multiple Stokes vector components measurement.
  • Each update of the controller state (a set of control voltages) needs N+l iterations, where N is the number of parameters (or equivalently the number of phase shifters). N iterations are used to calculate the partial derivatives numerically. N+l iteration is needed for the Kalman filter correction vector calculation and update of the base state.
  • Jacobi matrix for Kalman filter is obtained by using numerical derivatives.
  • SI, S1+S2 or S1+S2+S3 measurements can be used for error calculation in the algorithm.
  • x is the estimated state
  • z is a target state in the Stokes domain
  • h is a measured state in Stokes domain
  • P is a state error covariance
  • A is a transition matrix (set as an identity matrix in the RSOP control case)
  • H is a Jacobi matrix
  • Q and R are the process and measurement noise covariance matrices respectively
  • K is the Kalman gain
  • a is a leakage coefficient
  • apriori state and error covariance are written as x t ⁇ and P k ⁇
  • aposteriori state and error covariance are written as x and P k
  • k is the iteration number.
  • FIG. 3 shows the adaptation cycle including the calculation of numerical derivatives and Jacobi matrix, and Kalman adaptation.
  • Our novel approach is based on the application of selected ideas of optimization theory to the dynamic physical signal distortion problems such as tracking/equalizing polarization instability. Partial numerical derivatives with respect to control parameters are obtained in the phase-shifters based hardware, input to Jacobi matrix and used for adaptation in Kalman algorithmic cycle. State vector leakage is applied to achieve the target of range limited of control signals supplied to the phase shifters.
  • Our proposed (and tested in simulation and in the laboratory) algorithm achieves reset free multiobjective (i.e., S1+S2) Kalman filter based control of the polarization state.
  • Our algorithm is suitable for promising compact SiPho based implementation relying on manipulation of the lightwave by phase shifters, but our algorithm can be also efficiently used in LiNbO3 polarization controllers.
  • the phase shifter is set to ⁇ 0i+AO, 62, 03, 04 ⁇ .
  • phase shifter settings (phase shifter settings) is performed.
  • the phase shifter is set to ⁇ 0i, 02+A0, 03, 04 ⁇ .
  • the phase shifter is set to ⁇ 0i, 02, 03+A0, 04 ⁇ .
  • phase shifter settings (phase shifter settings) is performed.
  • the phase shifter is set to ⁇ 0i, 02, 03, O4+AO ⁇ .
  • phase shifter settings (phase shifter settings) is performed.
  • FIG. 4 shows a method 400 for polarization control.
  • the method 400 is performed by the device as shown in FIG. 1, and the PC shown in FIG. 2.
  • the method 400 includes a step 401 of separating an input optical signal into a first optical signal and a second optical signal.
  • the method 400 further includes a step 402 of obtaining a third optical signal by phase shifting the first optical signal according to control parameters, where the control parameters are obtained by cyclic adaptation of Kalman filter algorithm based on basic control parameters.
  • the method 400 further includes a step 403 of obtaining an output optical signal by combining the second optical signal and the third optical signal.
  • the algorithm achieves high-speed (e.g. lOOkRad/s) reset-free polarization tracking and equalization in the optical domain cause multiplication of the state vector by the leakage coefficient leads to the parameters (phases or voltages) constraining to a limited range, using 4 phase shifters also contributes to the reduction of the required range of control signal values (as compared to 3 or 2 phase shifters solution) allowing to achieve the optimum in terms of the tracking speed and the required control signal range applied to phase shifters. And multiple sources of information are used in the algorithm (e.g.
  • Kalman algorithmic procedure is a natural match for the multi -objective polarization control task, i.e., tracking that uses SI and S2 Stokes vector components instead of using only SI.
  • both tracking 1) to a desired SOP point on the Poincare sphere and 2) to the plane (or circle) on Poincare sphere is enabled by the algorithm, because in the algorithm, tracking can be switched from ‘point tracking’ to ‘circle tracking’ by the appropriate setting of the cost function.
  • the solution can be further enhanced by feedforward section but this would come at the cost of increased complexity.
  • more simplified versions of the same invented solution are possible such as reducing the number of photodiodes (4) and A/D converters (4) from 4 to 2, but this will come at a cost of somewhat reduced performance. It is feasible to include a simplified algorithm proposal as a separate embodiment.
  • FIG. 5 shows an application scenario.
  • the solution is a key potential enabler for the self-homodyne systems.
  • Various applications need a fast and real time polarization control/tracking solution.
  • self-homodyne detection is a promising technique.
  • the self-homodyne detection technique entails phase coherence of a modulated information bearing signal and the reference carrier signal as they originate from the same laser.
  • Self-homodyne detection has the following advantages: 1) relaxing the requirement for laser linewidth thereby allowing lower cost laser options and 2) the use of simplified RX DSP structure without carrier phase estimation (CPE) block.
  • CPE carrier phase estimation
  • the solution can be used in any application which requires stabilizing SOP of the signal or registering and tracking SOP variation events such as can be used in optical sensors.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

Les modes de réalisation de cette invention proposent un procédé de commande de polarisation et un dispositif associé. Le procédé comprend : la séparation d'un signal optique d'entrée en un premier signal optique et un deuxième signal optique; l'obtention d'un troisième et d'un quatrième signal optique par déphasage et couplage du signal optique d'entrée en fonction de paramètres de commande, les paramètres de commande étant obtenus par adaptation cyclique de l'algorithme du filtre de Kalman sur la base de paramètres de commande de base; l'obtention d'un signal optique de sortie par combinaison du troisième signal optique et du quatrième signal optique. La solution selon l'invention concerne l'amélioration de la résistance des systèmes de transmission optique à la rotation dynamique aléatoire de la polarisation.
PCT/RU2022/000197 2022-06-24 2022-06-24 Procédé de commande de polarisation et dispositif associé WO2023249509A1 (fr)

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Publication number Priority date Publication date Assignee Title
WO2021233207A1 (fr) * 2020-05-22 2021-11-25 华为技术有限公司 Dispositif et procédé de commande de polarisation

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021233207A1 (fr) * 2020-05-22 2021-11-25 华为技术有限公司 Dispositif et procédé de commande de polarisation

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
XIANG QIAN ET AL: "Adaptive Kalman filter for polarization and phase recovery in wide ranges of optical signal-to-noise ratio, polarization rotation frequency, and laser linewidth", OPTICAL ENGINEERING, SOC. OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, BELLINGHAM, vol. 57, no. 6, 1 June 2018 (2018-06-01), pages 66107, XP060107246, ISSN: 0091-3286, [retrieved on 20180608], DOI: 10.1117/1.OE.57.6.066107 *
ZHENG ZIBO ET AL: "Window-split structured frequency domain Kalman equalization scheme for large PMD and ultra-fast RSOP in an optical coherent PDM-QPSK system", OPTICS EXPRESS, vol. 26, no. 6, 9 March 2018 (2018-03-09), pages 7211, XP093020082, DOI: 10.1364/OE.26.007211 *

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