CN112039586A - OSNR measuring method, device and system based on digital signal processing - Google Patents

OSNR measuring method, device and system based on digital signal processing Download PDF

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CN112039586A
CN112039586A CN202010851176.3A CN202010851176A CN112039586A CN 112039586 A CN112039586 A CN 112039586A CN 202010851176 A CN202010851176 A CN 202010851176A CN 112039586 A CN112039586 A CN 112039586A
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equalizer
osnr
polarized
polarization state
coefficient
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张旭
李海波
曾韬
孟令恒
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Wuhan Research Institute of Posts and Telecommunications Co Ltd
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Wuhan Research Institute of Posts and Telecommunications Co Ltd
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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
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07953—Monitoring or measuring OSNR, BER or Q

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Abstract

The application relates to an OSNR measuring method, a device and a system based on digital signal processing, wherein the method comprises the following steps: using an equalizer to perform self-adaptive filtering processing on two groups of electric signals which are received coherently; extracting equalizer coefficients, and obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficients; obtaining a current polarization state evaluation parameter according to the Stokes vector; and obtaining the current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR. The OSNR measuring method based on digital signal processing is simple in measuring method and high in efficiency, can be suitable for the technical problems of links with optical filters and wavelength division multiplexing systems with high spectral efficiency, and is wide in application range.

Description

OSNR measuring method, device and system based on digital signal processing
Technical Field
The present disclosure relates to the field of coherent optical communication systems, and in particular, to an OSNR measurement method, device and system based on digital signal processing.
Background
At present, optical communication is continuously developing towards higher speed, larger capacity and longer distance, and coherent optical communication is more and more widely applied. The performance monitoring of the coherent optical signal becomes more important while improving the channel capacity and the transmission rate. The OSNR (optical signal to noise ratio) is a ratio of optical signal to noise, is an important parameter for evaluating the performance of the optical network, can directly reflect the quality of the signal, and is a main index for a network manager to know the working performance of the network system and evaluate the quality of an optical fiber link.
The conventional OSNR measurement method is an interpolation method, i.e. a linear interpolation value of noise power at two sides of an optical channel is used as an estimated value of noise power in a channel band to calculate a ratio of an optical signal peak value to the noise power to obtain an OSNR value, which is usually performed by a spectrometer. However, this method is not suitable for a link in which an optical filter device exists on the optical fiber link, and the noise power estimated by interpolation is not accurate. In addition, for wavelength division multiplexing systems with high spectral efficiency, such as 100Gbps DP-QPSK (dual polarization quadrature phase shift keying) signals with 50GHz channel spacing, interpolation is not suitable due to the overlapping of signal spectra between channels.
Disclosure of Invention
The embodiment of the application provides an OSNR measuring method, device and system based on digital signal processing, and aims to solve the technical problems that an interpolation method in the related technology cannot be applied to links with optical filters and wavelength division multiplexing systems with high spectral efficiency.
In a first aspect, an OSNR measuring method based on digital signal processing is provided, which includes the steps of:
using an equalizer to perform self-adaptive filtering processing on two groups of electric signals which are received coherently;
extracting equalizer coefficients, and obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficients;
obtaining a current polarization state evaluation parameter according to the Stokes vector;
and obtaining the current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR.
In some embodiments, after the adaptive filtering processing is performed on the two groups of coherently received electrical signals by using the equalizer, the method further includes the following steps:
outputting two groups of depolarization data, wherein the computing formula of the depolarization data output by the equalizer is as follows:
Figure BDA0002644779890000021
Figure BDA0002644779890000022
where n is the nth symbol period, L is the number of input data, L represents the number of input data, x and y represent the polarization directions, Eoutx(n) is the n-th equalizer output signal, Ein, corresponding to the x-polarizationx(n-l) is the n-l equalizer input signal, Ein, corresponding to the x-polarizationy(n-l) is the n-l equalizer input signal corresponding to the y polarization, Fxx(l) For the coefficients of the i-th x-polarized input signal to the x-polarized output signal, Fxy(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyx(l) For the coefficients of the i-th x-polarized input signal to the y-polarized output signal, Fyy(l) For the coefficients of the i-th y-polarized input signal to the y-polarized output signal, EoutyAnd (n) is the output signal of the nth equalizer corresponding to the y polarization.
In some embodiments, after extracting the equalizer coefficients, the method further comprises the steps of:
the equalizer coefficients are updated, and the calculation formula for updating the equalizer coefficients is as follows:
Fxx(l,g+1)＝Fxx(l,g)+4μxEoutx(n)[Einx(n-l)]*
Fxy(l,g+1)＝Fxy(l,g)+4μxEoutx(n)[Einy(n-l)]*
Fyx(l,g+1)＝Fyx(l,g)+4μyEouty(n)[Einx(n-l)]*
Fyy(l,g+1)＝Fyy(l,g)+4μyEouty(n)[Einy(n-l)]*
wherein g denotes an equalizer coefficient index before update, g +1 denotes an equalizer coefficient index after update, and Fxx(l,g)、Fxy(l,g)、Fyx(l,g)、Fyy(l, g) equalizer coefficients before update, Fxx(l,g+1)、Fxy(l,g+1)、Fyx(l,g+1)、Fyy(l, g +1) is the updated equalizer coefficient, μ is a slight incremental value for controlling the coefficient update speed,xis an error in the x-direction,yerror in the y-direction, Eoutx(n) is the n-th equalizer output signal, Ein, corresponding to the x-polarizationx(n-l) is the n-l equalizer input signal corresponding to the x-polarization, Eouty(n) is the nth equalizer output signal, Ein, corresponding to the y polarizationy(n-l) is the n-l equalizer input signal corresponding to the y polarization.
In some embodiments, the calculation formula of the error in the x direction and the error in the y direction is:
x＝1-Eoutx(n)[Eoutx(n)]*
y＝1-Eouty(n)[Eouty(n)]*
in some embodiments, the calculation formula for extracting the equalizer coefficients is:
Figure BDA0002644779890000041
Figure BDA0002644779890000042
Figure BDA0002644779890000043
Figure BDA0002644779890000044
wherein L is the number of input data, L represents the number of input data, Fxx(l) For the coefficients of the i-th x-polarized input signal to the x-polarized output signal, Fxy(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyx(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyy(l) Coefficient of the i-th y-polarized input signal to the y-polarized output signal, FxxFor the total coefficient, F, of the x-polarized input signal to the x-polarized output signalxyFor the total coefficient of y-polarized input signal to x-polarized output signal, FyxFor the total coefficient, F, of the x-polarized input signal to the y-polarized output signalyyIs the total coefficient of the y-polarized input signal to the y-polarized output signal.
In some embodiments, the current stokes vector describing the polarization state of the optical signal is obtained according to the equalizer coefficients by the following formula:
S0＝|Fxx|2+|Fxy|2
S1＝[|Fxx|2-|Fxy|2]/S0
S2＝-2Re(Fxx*Fxy)/S0
S3＝2Im(Fxx*Fxy)/S0
in the formula, S0Representing the magnitude of the optical power, S1、S2、S3To normalize the processed stokes vector.
In some embodiments, the calculation formula for obtaining the current polarization state estimation parameter according to the stokes vector is as follows:
Figure BDA0002644779890000045
wherein, sigma is the current polarization state evaluation parameter, n is the number of Stokes vectors continuously obtained in a preset time period,
Figure BDA0002644779890000051
as a stokes vector S1、S2、S3Average value over a predetermined period of time, S1(i) As the ith Stokes vector S1，
Figure BDA0002644779890000052
As the ith Stokes vector S2，
Figure BDA0002644779890000053
As the ith Stokes vector S3。
In some embodiments, before obtaining the current OSNR value according to the relationship between the preset polarization state estimation parameter and the OSNR, the method further includes:
under the condition that a plurality of OSNRs are known, an equalizer is used for respectively carrying out adaptive filtering processing on two groups of electric signals which are received coherently;
extracting equalizer coefficients, and obtaining a plurality of groups of corresponding Stokes vectors for describing the polarization state of the optical signal according to the equalizer coefficients;
obtaining a plurality of corresponding polarization state evaluation parameters according to the plurality of groups of corresponding Stokes vectors;
and obtaining a relation between a preset polarization state evaluation parameter and the OSNR according to the plurality of OSNRs and the plurality of corresponding polarization state evaluation parameters.
In a second aspect, there is provided an OSNR measuring apparatus based on digital signal processing, including:
the adaptive filter is used for carrying out adaptive filtering processing on the two groups of electric signals which are received coherently;
and the processor is used for extracting the equalizer coefficient, obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficient, obtaining a current polarization state evaluation parameter according to the Stokes vector, and obtaining a current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR.
In a third aspect, a digital signal processing based OSNR measuring system is provided, which is configured to perform the above digital signal processing based OSNR measuring method.
The beneficial effect that technical scheme that this application provided brought includes: the method is simple, high in efficiency, and wide in application range, and can be applied to the technical problems of links with optical filters and wavelength division multiplexing systems with high spectral efficiency.
The embodiment of the application provides an OSNR measuring method based on digital signal processing, which is characterized in that a Stokes vector for describing the polarization state of an optical signal is calculated through a digital signal processing algorithm by extracting an equalizer coefficient, a current polarization state evaluation parameter is obtained according to the Stokes vector, and a current OSNR value is obtained according to a relation between a preset polarization state evaluation parameter and an optical signal to noise ratio OSNR.
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In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a flowchart of an OSNR measurement method based on digital signal processing according to an embodiment of the present disclosure;
fig. 2 is a schematic process diagram of an OSNR measurement method based on digital signal processing according to an embodiment of the present application;
fig. 3 is a block diagram of an OSNR measuring apparatus based on digital signal processing according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1 and 2, the present application provides an OSNR measuring method based on digital signal processing, which includes the steps of:
s1: using an equalizer to perform self-adaptive filtering processing on two groups of electric signals which are received coherently;
s2: extracting equalizer coefficients, and obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficients;
s3: obtaining a current polarization state evaluation parameter according to the Stokes vector;
s4: and obtaining the current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR.
In the embodiment of the present application, in the stokes space, for the case of pure phase modulation with constant amplitude, the ideal DP-QPSK signal corresponds to 4 symbols shifted in one plane, while the noise is polarization independent, forming a sphere in the stokes space. At a receiving end, a Stokes vector of an optical signal is obtained through a digital signal processing algorithm, and according to the OSNR relation of the Stokes vector, the OSNR level of a current channel can be obtained by calculating the Stokes vector under the condition that various parameters of a communication link are not changed.
The OSNR measuring method based on digital signal processing provided by the embodiment of the application calculates the Stokes vector for describing the polarization state of the optical signal through a digital signal processing algorithm by extracting the coefficient of an equalizer, further obtains the current polarization state evaluation parameter according to the Stokes vector, and then obtains the current OSNR value according to the relation between the preset polarization state evaluation parameter and the optical signal to noise ratio OSNR.
Furthermore, in this embodiment of the present application, after performing adaptive filtering processing on two groups of coherently received electrical signals by using an equalizer, the method further includes the steps of:
outputting two groups of depolarization data, wherein the computing formula of the depolarization data output by the equalizer is as follows:
Figure BDA0002644779890000071
Figure BDA0002644779890000081
where n is the nth symbol period, L is the number of input data, L represents the number of input data, x and y represent the polarization directions, Eoutx(n) is the n-th equalizer output signal, Ein, corresponding to the x-polarizationx(n-l) is the n-l equalizer input signal, Ein, corresponding to the x-polarizationy(n-l) is the n-l equalizer input signal corresponding to the y polarization, Fxx(l) For the coefficients of the i-th x-polarized input signal to the x-polarized output signal, Fxy(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyx(l) For the coefficients of the i-th x-polarized input signal to the y-polarized output signal, Fyy(l) For the coefficients of the i-th y-polarized input signal to the y-polarized output signal, EoutyAnd (n) is the output signal of the nth equalizer corresponding to the y polarization.
Further, in the embodiment of the present application, after extracting the equalizer coefficients, the method further includes the steps of:
the equalizer coefficients are updated, and the calculation formula for updating the equalizer coefficients is as follows:
Fxx(l,g+1)＝Fxx(l,g)+4μxEoutx(n)[Einx(n-l)]*
Fxy(l,g+1)＝Fxy(l,g)+4μxEoutx(n)[Einy(n-l)]*
Fyx(l,g+1)＝Fyx(l,g)+4μyEouty(n)[Einx(n-l)]*
Fyy(l,g+1)＝Fyy(l,g)+4μyEouty(n)[Einy(n-l)]*
wherein g denotes an equalizer coefficient index before update, g +1 denotes an equalizer coefficient index after update, and Fxx(l,g)、Fxy(l,g)、Fyx(l,g)、Fyy(l, g) equalizer coefficients before update, Fxx(l,g+1)、Fxy(l,g+1)、Fyx(l,g+1)、Fyy(l, g +1) is the updated equalizer coefficient, μ is a slight incremental value for controlling the coefficient update speed,xis an error in the x-direction,yerror in the y-direction, Eoutx(n) is the n-th equalizer output signal, Ein, corresponding to the x-polarizationx(n-l) is the n-l equalizer input signal corresponding to the x-polarization, Eouty(n) is the nth equalizer output signal, Ein, corresponding to the y polarizationy(n-l) is the n-l equalizer input signal corresponding to the y polarization.
Further, in the embodiment of the present application, the calculation formula of the error in the x direction and the error in the y direction is:
x＝1-Eoutx(n)[Eoutx(n)]*
y＝1-Eouty(n)[Eouty(n)]*
further, in the embodiment of the present application, the calculation formula for extracting the equalizer coefficients is as follows:
Figure BDA0002644779890000091
Figure BDA0002644779890000092
Figure BDA0002644779890000093
Figure BDA0002644779890000094
wherein L is the number of input data, L represents the number of input data, Fxx(l) For the coefficients of the i-th x-polarized input signal to the x-polarized output signal, Fxy(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyx(l) For the coefficients of the i-th x-polarized input signal to the y-polarized output signal, Fyy(l) Coefficient of the i-th y-polarized input signal to the y-polarized output signal, FxxFor the total coefficient, F, of the x-polarized input signal to the x-polarized output signalxyFor the total coefficient of y-polarized input signal to x-polarized output signal, FyxFor the total coefficient of y-polarized input signal to x-polarized output signal, FyyIs the total coefficient of the y-polarized input signal to the y-polarized output signal.
Further, in the embodiment of the present application, the current stokes vector for describing the polarization state of the optical signal according to the equalizer coefficient is calculated by the following formula:
S0＝|Fxx|2+|Fxy|2
S1＝[|Fxx|2-|Fxy|2]/S0
S2＝-2Re(Fxx*Fxy)/S0
S3＝2Im(Fxx*Fxy)/S0
in the formula, S0Representing the magnitude of the optical power, S1、S2、S3To normalize the processed stokes vector. In the embodiment of the application, the obtained stokes vector for describing the polarization state of the optical signal is { S }1，S2，S3}。
Further, in the embodiment of the present application, a calculation formula for obtaining the current polarization state estimation parameter according to the stokes vector is as follows:
Figure BDA0002644779890000101
wherein, sigma is the current polarization state evaluation parameter, n is the number of Stokes vectors continuously obtained in a preset time period,
Figure BDA0002644779890000102
as a stokes vector S1、S2、S3Average value over a predetermined period of time, S1(i) As the ith Stokes vector S1，
Figure BDA0002644779890000103
As the ith Stokes vector S2，
Figure BDA0002644779890000104
As the ith Stokes vector S3。
Further, in this embodiment of the present application, before obtaining the current OSNR value according to the relationship between the preset polarization state estimation parameter and the OSNR, the method further includes the steps of:
under the condition that a plurality of OSNRs are known, an equalizer is used for respectively carrying out adaptive filtering processing on two groups of electric signals which are received coherently;
extracting equalizer coefficients, and obtaining a plurality of groups of corresponding Stokes vectors for describing the polarization state of the optical signal according to the equalizer coefficients;
obtaining a plurality of corresponding polarization state evaluation parameters according to the plurality of groups of corresponding Stokes vectors;
and obtaining a relation between a preset polarization state evaluation parameter and the OSNR according to the plurality of OSNRs and the plurality of corresponding polarization state evaluation parameters.
In the embodiment of the application, a relation between the polarization state evaluation parameter and the optical signal to noise ratio OSNR is obtained by testing the corresponding polarization state evaluation parameters under a plurality of OSNR conditions, and is preset, and in application, the OSNR level of the current channel is obtained by calculating the Stokes vector directly according to the relation between the preset polarization state evaluation parameter and the optical signal to noise ratio OSNR, so that the method is reliable.
Referring to fig. 3, an embodiment of the present application further provides an OSNR measuring apparatus based on digital signal processing, including:
the adaptive filter is used for carrying out adaptive filtering processing on the two groups of electric signals which are received coherently;
and the processor is used for extracting the equalizer coefficient, obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficient, obtaining a current polarization state evaluation parameter according to the Stokes vector, and obtaining a current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR.
It should be noted that, the processor in the embodiment of the present application may implement the above OSNR measuring method based on digital signal processing, which includes the steps of updating equalizer coefficients, calculating errors, extracting equalizer coefficients, calculating stokes vectors, and polarization state estimation parameters.
The OSNR measuring device based on digital signal processing provided by the embodiment of the application calculates the Stokes vector for describing the polarization state of the optical signal through a digital signal processing algorithm by extracting the coefficient of an equalizer, further obtains the current polarization state evaluation parameter according to the Stokes vector, and then obtains the current OSNR value according to the relation between the preset polarization state evaluation parameter and the optical signal to noise ratio OSNR.
The embodiment of the application also provides an OSNR measuring system based on digital signal processing, and the system is used for executing the OSNR measuring method based on digital signal processing.
The OSNR measuring system based on digital signal processing provided by the embodiment of the application calculates the Stokes vector for describing the polarization state of the optical signal through a digital signal processing algorithm by extracting the coefficient of an equalizer, further obtains the current polarization state evaluation parameter according to the Stokes vector, and then obtains the current OSNR value according to the relation between the preset polarization state evaluation parameter and the optical signal to noise ratio OSNR.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. An OSNR measuring method based on digital signal processing, comprising the steps of:
using an equalizer to perform self-adaptive filtering processing on two groups of electric signals which are received coherently;
extracting equalizer coefficients, and obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficients;
obtaining a current polarization state evaluation parameter according to the Stokes vector;
and obtaining the current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR.
2. The digital signal processing-based OSNR measuring method of claim 1, wherein after the adaptive filtering processing of the two sets of the electric signals received coherently using an equalizer, further comprising the steps of:
outputting two groups of depolarization data, wherein the computing formula of the depolarization data output by the equalizer is as follows:
Figure FDA0002644779880000011
Figure FDA0002644779880000012
where n is the nth symbol period, L is the number of input data, L represents the number of input data, x and y represent the polarization directions, Eoutx(n) is the n-th equalizer output signal, Ein, corresponding to the x-polarizationx(n-l) is the n-l equalizer input signal, Ein, corresponding to the x-polarizationy(n-l) is the n-l equalizer input signal corresponding to the y polarization, Fxx(l) For the coefficients of the i-th x-polarized input signal to the x-polarized output signal, Fxy(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyx(l) For the coefficients of the i-th x-polarized input signal to the y-polarized output signal, Fyy(l) For the coefficients of the i-th y-polarized input signal to the y-polarized output signal, EoutyAnd (n) is the output signal of the nth equalizer corresponding to the y polarization.
3. The digital signal processing based OSNR measuring method of claim 2, further comprising, after extracting the equalizer coefficients, the steps of:
the equalizer coefficients are updated, and the calculation formula for updating the equalizer coefficients is as follows:
Fxx(l，g+1)＝Fxx(l，g)+4μxEoutx(n)[Einx(n-l)]*
Fxy(l，g+1)＝Fxy(l，g)+4μxEoutx(n)[Einy(n-l)]*
Fyx(l，g+1)＝Fyx(l，g)+4μyEouty(n)[Einx(n-l)]*
Fyy(l，g+1)＝Fyy(l，g)+4μyEouty(n)[Einy(n-l)]*
wherein g represents the value before updateEqualizer coefficient index, g +1 denotes the updated equalizer coefficient index, Fxx(l，g)、Fxy(l，g)、Fyx(l，g)、Fyy(l, g) equalizer coefficients before update, Fxx(l，g+1)、Fxy(l，g+1)、Fyx(l，g+1)、Fyy(l, g +1) is the updated equalizer coefficient, μ is a slight incremental value for controlling the coefficient update speed,xis an error in the x-direction,yerror in the y-direction, Eoutx(n) is the n-th equalizer output signal, Ein, corresponding to the x-polarizationx(n-l) is the n-l equalizer input signal corresponding to the x-polarization, Eouty(n) is the nth equalizer output signal, Ein, corresponding to the y polarizationy(n-l) is the n-l equalizer input signal corresponding to the y polarization.
4. The digital signal processing-based OSNR measuring method of claim 3, wherein the x-direction error and the y-direction error are calculated by:
x＝1-Eoutx(n)[Eoutx(n)]*
y＝1-Eouty(n)[Eouty(n)]* 。
5. the digital signal processing-based OSNR measuring method of claim 1, wherein the calculation formula for extracting the equalizer coefficient is:
Figure FDA0002644779880000031
Figure FDA0002644779880000032
Figure FDA0002644779880000033
Figure FDA0002644779880000034
wherein L is the number of input data, L represents the number of input data, Fxx(l) For the coefficients of the i-th x-polarized input signal to the x-polarized output signal, Fxy(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyx(l) Coefficient of the i-th y-polarized input signal to the x-polarized output signal, Fyy(l) Coefficient of the i-th y-polarized input signal to the y-polarized output signal, FxxFor the total coefficient, F, of the x-polarized input signal to the x-polarized output signalxyFor the total coefficient of y-polarized input signal to x-polarized output signal, FyxFor the total coefficient, F, of the x-polarized input signal to the y-polarized output signalyyIs the total coefficient of the y-polarized input signal to the y-polarized output signal.
6. The digital signal processing-based OSNR measuring method of claim 5, wherein the current stokes vector describing the polarization state of the optical signal is obtained from the equalizer coefficients by the following formula:
S0＝|Fxx|2+|Fxy|2
S1＝[|Fxx|2-|Fxy|2]/S0
S2＝-2Re(Fxx*Fxy)/S0
S3＝2Im(Fxx*Fxy)/S0
in the formula, S0Representing the magnitude of the optical power, S1、S2、S3To normalize the processed stokes vector.
7. The digital signal processing-based OSNR measuring method of claim 6, wherein a calculation formula for obtaining the current polarization state estimation parameter according to the stokes vector is:
Figure FDA0002644779880000041
wherein, sigma is the current polarization state evaluation parameter, n is the number of Stokes vectors continuously obtained in a preset time period,
Figure FDA0002644779880000042
as a stokes vector S1、S2、S3Average value over a predetermined period of time, S1(i) As the ith Stokes vector S1，
Figure FDA0002644779880000043
As the ith Stokes vector S2，
Figure FDA0002644779880000044
As the ith Stokes vector S3。
8. The digital signal processing-based OSNR measuring method of claim 1, further comprising, before obtaining the current OSNR value according to a relation between a preset polarization state estimation parameter and an OSNR, the steps of:
under the condition that a plurality of OSNRs are known, an equalizer is used for respectively carrying out adaptive filtering processing on two groups of electric signals which are received coherently;
extracting equalizer coefficients, and obtaining a plurality of groups of corresponding Stokes vectors for describing the polarization state of the optical signal according to the equalizer coefficients;
obtaining a plurality of corresponding polarization state evaluation parameters according to the plurality of groups of corresponding Stokes vectors;
and obtaining a relation between a preset polarization state evaluation parameter and the OSNR according to the plurality of OSNRs and the plurality of corresponding polarization state evaluation parameters.
9. An OSNR measuring apparatus based on digital signal processing, comprising:
the adaptive filter is used for carrying out adaptive filtering processing on the two groups of electric signals which are received coherently;
and the processor is used for extracting the equalizer coefficient, obtaining a current Stokes vector for describing the polarization state of the optical signal according to the equalizer coefficient, obtaining a current polarization state evaluation parameter according to the Stokes vector, and obtaining a current OSNR value according to a relation between a preset polarization state evaluation parameter and the OSNR.
10. An OSNR measurement system based on digital signal processing, wherein the system is configured to perform the OSNR measurement method based on digital signal processing according to any one of claims 1 to 8.
CN202010851176.3A 2020-08-21 2020-08-21 OSNR measuring method, device and system based on digital signal processing Pending CN112039586A (en)

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