CN110168967A - A kind of photoreceiver and time-delay estimation method - Google Patents

A kind of photoreceiver and time-delay estimation method Download PDF

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CN110168967A
CN110168967A CN201780082891.1A CN201780082891A CN110168967A CN 110168967 A CN110168967 A CN 110168967A CN 201780082891 A CN201780082891 A CN 201780082891A CN 110168967 A CN110168967 A CN 110168967A
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CN110168967B (en
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卢彦兆
李良川
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Huawei Technologies 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

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Abstract

A kind of photoreceiver and time-delay estimation method, the photoreceiver include: analogue signal processor, for carrying out photoelectric conversion processing to received optical signal, obtain electric signal；Digital signal processor obtains frequency-region signal for carrying out time-frequency conversion processing to electric signal；Delay estimator, for according to the frequency-region signal, the second sub- frequency-region signal of the first sub- frequency-region signal of the in-phase component of the optical signal and the quadrature component of the optical signal is obtained, and calculates the phase difference of the in-phase component and the quadrature component according to the described first sub- frequency-region signal and the second sub- frequency-region signal；Compensation of delay device, for carrying out compensation of delay to the optical signal using the phase difference.

Description

Optical receiver and time delay estimation method Technical Field
The embodiment of the invention relates to the technical field of communication, in particular to an optical receiver and a time delay estimation method.
Background
Transmission band for optical fiber transmission system with rapid expansion of data communication serviceThe width and capacity requirements are becoming higher and higher. Currently, 100G-Wavelength Division Multiplexing (WDM) transmission systems are In large commercial use, the single-wave transmission rate will evolve to 400Gbps even 1Tbps, and high-order modulation and high-symbol modulation rate can be used to increase the single-wave transmission rate, but In coherent detection systems, both the high-order modulation and high-symbol modulation rate have higher requirements for In-phase and quadrature (IQ) delay between an In-phase component and a quadrature component, where i (t) Acos2 pi ft is typically called an In-phase component if the modulated optical signal is represented, and q (t) Asin2 pi ft is typically called a quadrature component, where f is fcIs the carrier frequency and f is the baseband signal frequency. At the optical receiver end, the received modulated optical signal is demodulated and photoelectrically converted to obtain an in-phase component I 'and a quadrature component Q' of the modulated optical signal in the form of an electrical signal, and the delay generated by the in-phase component I 'and the quadrature component Q' in the transmission process of the respective channels is the quadrature delay.
Then, in order to reduce the influence of the orthogonal delay on the single wave transmission rate, in the prior art, a 4 × 4 Multiple Input Multiple Output (MIMO) filter is used to perform blind compensation on the orthogonal delay, that is, the size of the orthogonal delay does not need to be estimated, only the adaptive FIR (fine Impulse response) filter 4x4-MIMO is used to perform delay compensation, and the FIR filter can automatically converge to the optimal state for compensating the orthogonal delay by constructing a cost function. The compensation accuracy of this method is related to the filter complexity and requires real-time updating for each modulation symbol, which is higher than the complexity of the conventional 2x2-MIMO filter. Then, in order to reduce the complexity of compensation, the delays generated by the in-phase component I 'and the quadrature component Q' during the transmission of the respective channels may be estimated, and the obtained quadrature delay may be used to compensate the delay of the in-phase component I 'or the quadrature component Q'.
At present, no optical receiver for better estimating the orthogonal delay is proposed in the prior art.
Disclosure of Invention
The embodiment of the invention provides an optical receiver and a delay estimation method, which are used for providing a novel optical receiver.
In a first aspect, an optical receiver is provided. In the optical receiver, the analog signal processor is configured to perform photoelectric processing on the received optical signal to obtain an electrical signal. Then, the digital signal processor carries out time-frequency transformation processing on the electric signals to obtain frequency domain signals. Then, a first sub-frequency domain signal of the in-phase component of the optical signal and a second sub-frequency domain signal of the quadrature component of the optical signal are obtained by the delay estimator according to the frequency domain signals, and the phase difference of the in-phase component and the quadrature component is calculated according to the first sub-frequency domain signal and the second sub-frequency domain signal. Finally, the optical signal is delayed and compensated by the delay compensator by using the phase difference.
In the embodiment of the invention, the time delay estimator obtains the frequency domain signal, obtains the first sub-frequency domain signal of the in-phase component of the optical signal received by the optical receiver and the second sub-frequency domain signal of the quadrature component of the optical signal according to the frequency domain signal, and further calculates the phase difference of the in-phase component and the quadrature component according to the first sub-frequency domain signal and the second sub-frequency domain signal, so that the time delay compensator performs time delay compensation on the received optical signal by using the phase difference.
In one possible design, when calculating the phase difference between the in-phase component and the quadrature component according to the first sub-frequency-domain signal and the second sub-frequency-domain signal, the delay estimator is specifically configured to: obtaining a first signal component and a second signal component according to the first sub-frequency domain signal; wherein the first signal component and the second signal component are used to extract a first phase angle of the in-phase component; obtaining a third signal component and a fourth signal component according to the second sub-frequency domain signal; wherein the third signal component and the fourth signal component are used to extract a second phase angle of the quadrature component; calculating a phase difference between the in-phase component and the quadrature component from the first signal component, the second signal component, the third signal component, and the fourth signal component.
In the embodiment of the invention, the first phase angle of the in-phase component is extracted by using the first signal component and the second signal component, and the second phase angle of the orthogonal component is extracted by using the third signal component and the fourth signal component, so that the influence that the phase angles of the in-phase component and the orthogonal component cannot be accurately extracted due to the existence of intersymbol crosstalk can be reduced, the accuracy of extracting the phase angles of the in-phase component and the orthogonal component can be improved, and the accuracy of delay estimation can be further improved.
In one possible design, when obtaining the first signal component and the second signal component according to the first sub-frequency domain signal, the delay estimator is specifically configured to: obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point; the delay estimator, when obtaining a third signal component and a fourth signal component according to the second sub-frequency domain signal, is specifically configured to: obtaining the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point; wherein L is at least a distance separated from a center frequency point of a frequency spectrum of the first or second sub-frequency domain signal by half a symbol rate, N is an integer greater than zero and less than N, and N is equal to the frequency point number of the time-frequency transformation minus L plus 1.
In this embodiment of the present invention, L is at least a distance separated by half a symbol rate from a center frequency point of a frequency spectrum of the first sub-frequency domain signal or the second sub-frequency domain signal, and can effectively distinguish a frequency component of an nth frequency point from a frequency component of an n + L th frequency point, so that a first phase angle of an in-phase component can be effectively extracted by using the first signal component and the second signal component, and a second phase angle of an orthogonal component can be extracted by using the third signal component and the fourth signal component.
In one possible design, where NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsIs the sampling rate; the delay estimationThe calculator is specifically configured to, when obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point: multiplying the frequency component of the first sub-frequency domain signal at the nth frequency point by the conjugate of the frequency component at the (n + L) th frequency point to obtain the first signal component; multiplying the frequency component of the first sub-frequency domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point to obtain the second signal component.
In the embodiment of the present invention, the frequency component of the first sub-frequency domain signal at the nth frequency point is multiplied by the conjugate of the frequency component at the (n + L) th frequency point to obtain the first signal component, that is, the amplitudes of the first sub-frequency domain signal at the nth frequency point and the (n + L) th frequency point are multiplied, and the phases of the first sub-frequency domain signal at the nth frequency point and the (n + L) th frequency point are subtracted, so that the phase difference between the nth frequency point and the (n + L) th frequency point can be easily obtained, and the first phase angle of the in-phase component is extracted.
In a possible design, when the delay estimator multiplies the frequency component of the first sub-frequency domain signal at the nth frequency point by the conjugate of the frequency component at the n + L frequency point to obtain the first signal component, the delay estimator is specifically configured to: traversing N from 1 to N to obtain N first sub-signal components; adding the N first sub-signal components to obtain the first signal component; the delay estimator is configured to, when the second signal component is obtained by multiplying the frequency component of the first sub-frequency-domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point, specifically: traversing N from 1 to N to obtain N second sub-signal components; and adding the N second sub-signal components to obtain the second signal component.
In the embodiment of the invention, the frequency components of the N pairs of frequency points are subjected to conjugate multiplication, and N first sub-signal components and N second sub-signal components are obtained and added, namely, the phase difference of the N pairs of frequency points is added and then averaged, so that the accuracy of extracting the first phase angle of the in-phase component according to the first signal component and the second signal component is improved, and the accuracy of delay estimation can be further improved.
In one possible design, L is equal to L1+ M, wherein, NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsM is an integer greater than zero for the sampling rate; the delay estimator is specifically configured to, when obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point: for each value of M, the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the n + L1Conjugate multiplication of frequency components at + M frequency points to obtain the first signal component, and obtain a plurality of first signal components in total; for each value of M, the first sub-frequency domain signal is positioned at the n + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the n + M frequency points to obtain the second signal components, and obtaining a plurality of second signal components; the delay estimator is specifically configured to, when obtaining the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point: for each value of M, the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the n + L1Conjugate multiplication of frequency components at + M frequency points to obtain the third signal component, and obtain a plurality of third signal components in total; for each value of M, the second sub-frequency domain signal is positioned at the n + L1And multiplying the frequency components at the frequency points by the conjugates of the frequency components at the n + M frequency points to obtain the fourth signal components, and obtaining a plurality of fourth signal components in total.
In the embodiment of the present invention, when M takes different values, a plurality of different first signal components, a plurality of different second signal components, a plurality of different third signal components, and a plurality of different fourth signal components can be obtained, and then a plurality of different phase differences between the in-phase component and the quadrature component can be obtained by using the plurality of different first signal components, the plurality of different second signal components, the plurality of different third signal components, and the plurality of different fourth signal components, and then the plurality of different phase differences are processed to reduce an error in obtaining a phase difference between the in-phase component and the quadrature component, thereby improving accuracy of delay estimation.
In one possible design, L is equal to L1+ M, wherein, NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsM is an integer greater than zero for the sampling rate; the delay estimator is specifically configured to, when obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point: for the first value of M, traversing N from 1 to N, and comparing the frequency component of the first sub-frequency domain signal at the nth frequency point with the frequency component at the N + L1Conjugate multiplication of frequency components at + M frequency points to obtain N first sub-signal components; adding the N first sub-signal components to obtain the first signal component; the first value is any one value of M; for the first value of M, traversing N from 1 to N, and enabling the first sub-frequency domain signal to be at the N + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the N + M frequency points to obtain N second sub-signal components; adding the N second sub-signal components to obtain the second signal component; for a plurality of values of M, obtaining a plurality of first signal components and a plurality of second signal components; the delay estimator is specifically configured to, when obtaining the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point: for the first value of M, N is traversed from 1 to N, and the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the N + L1Multiplying the conjugates of the frequency components at + M frequency points to obtain N third sub-signal components, and adding the N third sub-signal components to obtain the third signal component; for the first value of M, traversing N from 1 to N, and enabling the second sub-frequency domain signal to be at the N + L1Frequency at a frequency pointMultiplying the components by the conjugate of the frequency components at the N + M frequency points to obtain N fourth sub-signal components, and adding the N fourth sub-signal components to obtain the fourth signal component; for a plurality of values of M, a plurality of third signal components and a plurality of fourth signal components are obtained.
In the embodiment of the invention, the delay estimator adds the N first sub-signal components to obtain a first signal component and adds the N second sub-signal components to obtain a second signal component during the process of passing N; adding the N third sub-signal components to obtain a third signal component, adding the N fourth sub-signal components to obtain a fourth signal component, which reduces errors in extracting phase differences between different frequency points of the first sub-frequency domain signal and between different frequency points of the second sub-frequency domain signal, thereby improving accuracy in extracting a first phase angle of the in-phase component and a second phase angle of the quadrature component, and further improving accuracy in estimating delay time, further, when M takes different values, a plurality of different first signal components, a plurality of different second signal components, a plurality of different third signal components, and a plurality of different fourth signal components can be obtained, and a plurality of phase differences between the in-phase component and the quadrature component can be obtained by using the plurality of different first signal components, the plurality of different second signal components, the plurality of different third signal components, and the plurality of different fourth signal components, and further processing a plurality of different phase differences to reduce the error of obtaining the phase difference between the in-phase component and the quadrature component, and further improving the accuracy of the delay estimation from the other dimension.
In a possible design, when the delay estimator calculates the phase difference between the in-phase component and the quadrature component according to the first signal component, the second signal component, the third signal component, and the fourth signal component, the delay estimator is specifically configured to: obtaining a plurality of first phase angles of the in-phase component from first and second signal components corresponding to the same M of the plurality of first and second signal components, and obtaining a plurality of second phase angles of the quadrature component from third and fourth signal components corresponding to the same M of the plurality of third and fourth signal components; subtracting a first phase angle and a second phase angle which correspond to the same M in the plurality of first phase angles and the plurality of second phase angles to obtain a plurality of phase differences; calculating an average phase difference of the plurality of phase differences, and determining the average phase difference as the phase difference of the in-phase component and the quadrature component.
In the embodiment of the present invention, when M takes different values, phase differences of a plurality of in-phase components and orthogonal components are obtained, then an average phase difference of the plurality of phase differences is calculated, and the average phase difference is used as a phase difference of the orthogonal components and the orthogonal components, that is, the obtained plurality of phase differences are filtered by a filter. And filtering the plurality of phase differences to reduce an error of obtaining the phase difference between the in-phase component and the quadrature component, thereby improving the accuracy of the delay estimation.
In a possible design, when the delay compensator performs delay compensation on the optical signal by using the phase difference, the delay compensator is specifically configured to: and adjusting the phase of the first sub-frequency domain signal or the second sub-frequency domain signal by using the phase difference to complete the delay compensation of the optical signal.
In the embodiment of the invention, the delay compensator utilizes the phase difference to carry out phase adjustment on the frequency domain signal in the frequency domain, and the compensation process is simpler because the phase of the frequency domain signal is directly adjusted.
In a possible design, when the delay compensator performs delay compensation on the optical signal by using the phase difference, the delay compensator is specifically configured to: and adjusting the time delay of an analog converter in the analog signal processor by using the time delay obtained by the time delay estimator according to the phase difference so as to complete the time delay compensation of the optical signal.
In the embodiment of the invention, the delay compensator can also utilize the delay to adjust the delay of the analog-to-digital converter in the analog signal processor in the time domain, and the compensation process is simpler because the delay of the analog converter is directly adjusted.
In a second aspect, a delay estimation method is provided, the method comprising the steps performed by a delay estimator of the optical receiver of the first aspect.
In a third aspect, a delay estimator is provided, which includes a receiving module, an obtaining module, and a calculating module, where the module included in the delay estimator is configured to execute the delay estimation method in the second aspect.
In a fourth aspect, a delay estimator is provided, which in one possible design comprises a processor configured to support the delay estimator to perform the corresponding functions in the delay estimation method in the second aspect. The delay estimator may further comprise a memory coupled to the processor for storing program instructions and data necessary for the delay estimator.
The embodiment of the invention provides an optical receiver, in the optical receiver, a time delay estimator obtains a frequency domain signal, a first sub-frequency domain signal of an in-phase component of an optical signal received by the optical receiver and a second sub-frequency domain signal of an orthogonal component of the optical signal are obtained according to the frequency domain signal, and then a phase difference of the in-phase component and the orthogonal component is calculated according to the first sub-frequency domain signal and the second sub-frequency domain signal, so that a time delay compensator performs time delay compensation on the received optical signal by using the phase difference.
Drawings
FIG. 1 is a system architecture diagram of an optical network system;
fig. 2 is a schematic structural diagram of an optical receiver in an optical network system;
fig. 3 is a schematic structural diagram of an optical receiver according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of L in an embodiment of the present invention;
fig. 5 is a flowchart of a delay estimation method according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a delay estimator according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a delay estimator according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
Hereinafter, some terms in the embodiments of the present invention are explained to facilitate understanding by those skilled in the art.
(1) An Optical Line Terminal (OLT) is an important local side device, the OLT is connected to a front-end device, such as a convergence layer switch, through a network cable, and the OLT is connected to an Optical splitter of a user side through a single Optical fiber. The OLT may implement functions of controlling, managing, and ranging a customer premise equipment, where one customer premise equipment is, for example, an Optical Network Unit (ONU). And the OLT can convert the received electric signals into optical signals, and is photoelectric integrated equipment.
(2) An Optical Network Unit (ONU) is divided into an active Optical Network Unit and a passive Optical Network Unit, and the ONU may also be an Optical and electrical integrated device.
(3) An in-phase component and a quadrature component, where i (t) Acos (2 pi ft) is typically referred to as the in-phase component and q (t) Asin (2 pi ft) is typically referred to as the quadrature component, where fcFor the carrier frequency, f is the baseband signal frequency, and the in-phase component i (t) and quadrature component q (t) are ideally in quadrature.
(4) In addition, the term "and/or" herein is only one kind of association relationship describing an associated object, and means that there may be three kinds of relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship, unless otherwise specified. Moreover, in the description of the embodiments of the present invention, the terms "first," "second," and the like are used for descriptive purposes only and not for purposes of indicating or implying relative importance, nor for purposes of indicating or implying order.
To better describe the optical receiver in the embodiment of the present invention, an application scenario of the embodiment of the present invention, that is, a system architecture of an optical network system, is described first, please refer to fig. 1. In fig. 1, an optical transmitter and an optical receiver are included, and the optical transmitter transmits an optical signal to the optical receiver through an optical fiber without distortion. The optical network system in the embodiment of the present invention may be a Nyquist system or a Faster-Than-Nyquist (FTN) system, which is not limited in the embodiment of the present invention.
To more clearly describe the optical receiver in the embodiment of the present invention, the optical receiver in the optical network system shown in fig. 1 is described below, please refer to fig. 2. The optical receiver is located in the OLT and/or the ONU, and comprises an analog signal processor and a digital signal processor:
the analog signal processor comprises the following parts:
a 90-degree mixer (90 ° Hybrid) coupled to four photoelectric converters in the optical receiver, so that there are four channels between the 90-degree mixer and the four photoelectric converters, and 4-channel signal components are output. For example, light with the same wavelength generates two mutually independent and orthogonal polarized lights through a polarizer in an optical transmitter, and the two polarized lights are respectively modulated to obtain two polarized light signals, which are denoted as a first polarized light signal x and a second polarized light signal y. The optical transmitter transmits the first polarized optical signal x and the second polarized optical signal y to the optical receiver. The optical receiver receives the first polarized optical signal x and the second polarized optical signal y through the 90-degree hybrid interface, and outputs four optical signals corresponding to four channel signal components, wherein the four channel signal components are in-phase components x of the first polarized optical signaliOrthogonal component x of the first polarized optical signalqIn-phase component y of the second polarized light signaliAnd the orthogonal component y of the second polarized optical signalq。
And the Optical-to-Electrical converter (O/E) is coupled with the 90-degree mixer and used for detecting the four Optical signals output by the 90-degree mixer, converting the four Optical signals into four Electrical signals and outputting the four Electrical signals.
An Analog-to-Digital Converter (ADC) coupled to the photoelectric Converter for converting the four electrical signals output by the photoelectric Converter into Digital signals, where the Digital signals are also quantized Digital data stream xi、xq、yiAnd yq。
A digital signal processor connected to the analog-to-digital converter in the analog signal processor for quantizing the four digital data streams xi、xq、yiAnd yqFurther processing is carried out.
In the prior art, for example, the optical receiver shown in fig. 2, it cannot be guaranteed that the lengths of the four channels from the output of the 90-degree mixer to the input of the analog-to-digital converter are all equal, that is, the length of the optical fiber from the output of the 90-degree mixer to the input of the optical-to-electrical converter and the length of the cable from the output of the optical-to-electrical converter to the input of the analog-to-digital converter are all equal, so that the optical signal is delayed in the transmission process, thereby affecting high-order modulation and high symbol modulation rate.
In view of the above, an embodiment of the present invention provides an optical receiver, after the optical receiver receives a polarized optical signal transmitted by an optical transmitter, the polarized optical signal is processed by a 90 mixer, an optical-to-electrical converter, and an analog-to-digital converter of the optical receiver to obtain a processed signal, where the processed signal is a time domain signal, the processed signal enters a digital signal processor, the digital signal processor performs Fast Fourier Transform (FFT) on the processed signal, that is, converts the time domain signal into a frequency domain signal, the frequency domain signal enters a delay estimator, the delay estimator obtains a first sub-frequency domain signal of an in-phase component of the received optical signal and a second sub-frequency domain signal of an orthogonal component of the received optical signal according to the frequency domain signal, so as to calculate a phase difference between the in-phase component and the orthogonal component according to the first sub-frequency domain signal and the second sub-frequency domain signal, the obtained phase difference enters a delay compensator, and the delay compensator performs delay compensation on the received optical signal by using the obtained phase difference, namely, the embodiment of the invention provides an optical receiver.
The following describes the technical solution provided by the embodiment of the present invention with reference to the accompanying drawings, and in the following description, the technical solution provided by the present invention is applied to the application scenario shown in fig. 1 as an example.
Referring to fig. 3, an embodiment of the present invention provides an optical receiver, which can be applied in the application scenario shown in fig. 1, and the receiver includes:
the analog signal processor 301 is configured to perform a photoelectric conversion process on the received optical signal to obtain an electrical signal.
Light with the same wavelength passes through a polarizing film in an optical transmitter to generate two paths of mutually independent and orthogonal polarized light, the optical transmitter modulates the two paths of polarized light respectively to obtain two paths of polarized light signals, the two paths of polarized light signals are marked as a first polarized light signal x and a second polarized light signal y, and the optical transmitter sends the first polarized light signal x and the second polarized light signal y to an optical receiver. Therefore, in the embodiment of the present invention, the optical signal received by the optical receiver may include two paths of polarized optical signals, that is, a first polarized optical signal x and a second polarized optical signal y, where a signal expression corresponding to the first polarized optical signal x and a signal expression corresponding to the second polarized optical signal y are both in a complex form, and polarization directions of the first polarized optical signal x and the second polarized optical signal y are perpendicular to each other.
Hereinafter, an optical receiver according to an embodiment of the present invention will be described by taking one of the two polarized optical signals as an example.
In the embodiment of the present invention, the analog signal processor includes the 90-degree mixer, the photoelectric converter and the analog-to-digital converter shown in fig. 2, wherein the 90-degree mixer in the optical receiver outputs two optical signals corresponding to two channel signal components after receiving the optical signal, for example, the two optical signalsThe received optical signal is exemplified by a first polarized optical signal x, and the two channel signal components are respectively an in-phase component x of the first polarized optical signal xiAnd the orthogonal component xqIn-phase component xiAnd the orthogonal component xqEnters a photoelectric converter, outputs two paths of electric signals after photoelectric conversion, and further, the electric signals output by the photoelectric converter are processed by an analog-to-digital converter to output two paths of quantized signals xiAnd xq。
The digital signal processor 302 is configured to perform time-frequency transformation on the electrical signal to obtain a frequency domain signal.
The digital signal processor 302 receives the electrical signal outputted from the analog signal processor, which is referred to as the two-path quantized signal xiAnd xqAnd performing FFT on the two paths of quantized electric signals.
In the digital signal processor 302, the quantized two-path signal x is receivediAnd xqBefore FFT processing, the two quantized signals x are firstly processediAnd xqCombining to obtain a complex signal x ═ xi+jxqThen, FFT conversion is performed on the complex signal to obtain a frequency domain signal FX (N)fft) Wherein, the complex signal x ═ xi+jxqFor time-domain signals, NfftThe number of frequency points representing the FFT, for example, equal to a value from 0 to 4095; FX is a frequency domain signal of the time domain complex signal x.
The delay estimator 303 is configured to obtain a first sub-frequency-domain signal of an in-phase component of the optical signal and a second sub-frequency-domain signal of a quadrature component of the optical signal according to the frequency-domain signal, and calculate a phase difference between the in-phase component and the quadrature component according to the first sub-frequency-domain signal and the second sub-frequency-domain signal.
In the embodiment of the present invention, the delay estimator 303, which may be a chip or an integrated circuit, receives the frequency domain signal output by the digital signal processor 302. The following describes a method for the delay estimator 303 to obtain the first sub-frequency-domain signal and the second sub-frequency-domain signal according to the frequency-domain signal.
In the embodiment of the present invention, before the FFT processing by the digital signal processor 302Time domain signal x ═ xi+jxqThe frequency domain signal is a complex signal after the FFT processing, and the delay estimator 303 performs mathematical transformation on the frequency domain signal to obtain the in-phase component x of the received optical signaliAnd the quadrature component x of the received optical signalqIs shown.
In one embodiment, the delay estimator 303 adds the sequence of the frequency domain signal to the conjugate of the symmetric sequence of the sequence and divides by 2 to obtain the in-phase component xiOf the first sub-frequency domain signal, i.e.
The delay estimator 303 subtracts the conjugate of the sequence of the frequency domain signal and the symmetric sequence of the sequence, and divides the subtracted result by 2j to obtain the orthogonal component xqOf the second sub-frequency domain signal, i.e.
Wherein, FXI (N)fft) For the in-phase component x of the time-domain signal xiFrequency domain signal of, FXQ (N)fft) For the quadrature component x of the time-domain signal xqOf the frequency domain signal. FXR(Nfft)＝[FX(1)，FX(end：-1:2)]FX (end: -1:2) denotes the sequence of FX with the frequency component of coordinate 1 unchanged for coordinates 2 to NfftInversion of the corresponding frequency component, FXR(Nfft) Is a symmetric FX sequence, where coordinate 1 on the FX sequence corresponds to the FX spectrum center bin.
In the embodiment of the present invention, if the quantized two-path signal x is directly processed in the digital signal processor 302, the two-path signal x is processediAnd xqPerforming FFT to obtain a time domain signal xiFrequency domain signal FXI and time domain signal xqSuch that the above-described step of mathematically transforming the frequency domain signal is not performed in the delay estimator 303.
In this embodiment of the present invention, after the delay estimator 303 acquires the first sub-frequency domain signal and the second sub-frequency domain signal, if a phase difference between the in-phase component and the orthogonal component is to be calculated, a first phase angle of the in-phase component and a second phase angle of the orthogonal component are to be acquired, specifically, the delay estimator 303 needs to calculate and obtain two delay-related signal components, namely, a first signal component and a second signal component, according to the first sub-frequency domain signal, and calculate and obtain two delay-related signal components, namely, a third signal component and a fourth signal component, according to the second sub-frequency domain signal, so as to acquire a phase difference between the in-phase component and the orthogonal component by using the first signal component, the second signal component, the third signal component and the fourth signal component.
The optical receiver provided by the embodiment of the invention can be applied to a Nyquist system and can also be applied to a super-Nyquist system. When applied to the super-nyquist system, Inter-Symbol Interference (ISI) is caused by the super-nyquist system transmitting at the super-nyquist Symbol rate. In order to reduce the influence of inter-code crosstalk on the extraction of the phase angles of the in-phase component and the orthogonal component, in the embodiment of the present invention, an analog signal processor 301 in the optical receiver performs photoelectric conversion on a received optical signal to obtain an electrical signal, the electrical signal enters a digital signal processor 302, the digital signal processor 302 performs time-frequency transform processing on the electrical signal, that is, performs FFT on a complex signal x to obtain a frequency domain signal FX of x, and a delay estimator 303 obtains the phase difference between the in-phase component and the orthogonal component of the received optical signal by using the frequency domain signal FX, where the more the frequency points are, the better the original electrical signal can be recovered, the better the phase angles of the in-phase component and the orthogonal component can be extracted, so as to improve the accuracy of delay estimation.
In the embodiment of the present invention, in fact, the delay estimator 303 may also adopt a mode of extracting the first phase angle of the in-phase component through the first signal component or the second signal component, and therefore, the above-mentioned mode of extracting the first phase angle of the in-phase component through the first signal component and the second signal component is adopted because the first phase angle of the in-phase component may not be accurately extracted due to the presence of inter-symbol crosstalk in the beyond nyquist system.
When the delay estimator 303 extracts the first phase angle of the in-phase component by extracting the phase angle from the first signal component or the second signal component, the first signal component is calculated only by using the first sub-frequency domain signal, and the first signal component and the second signal component are not required to be calculated at the same time, so that the calculation complexity can be reduced.
If the optical receiver provided by the embodiment of the present invention is not applied to the faster-than-nyquist system, or is not applied to a system similar to the faster-than-nyquist system, or is applied to a system capable of eliminating inter-symbol interference, the delay estimator 303 may extract the phase angle through the first signal component or the second signal component, or extract the phase angle through the first signal component and the second signal component, and may be selected according to the situation. For example, when the optical receiver provided by the embodiment of the present invention is applied in the nyquist system, the delay estimator 303 may extract the first phase angle of the in-phase component in any one of a manner of extracting the first phase angle of the in-phase component by the first signal component or the second signal component, or a manner of extracting the first phase angle of the in-phase component by the first signal component and the second signal component.
The method for acquiring the signal component by the delay estimator 303 is described below, and in the following description, the first signal component and the second signal component are taken as an example. Accordingly, the third signal component and the fourth signal component may also be obtained by the following method, which is not described herein again.
In one embodiment, the delay estimator 303 may obtain the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the n + L frequency point.
The frequency component of the first sub-frequency-domain signal at the nth frequency point and the frequency component at the n + L th frequency point each exhibit a complex form, including an amplitude and a phase.
In the embodiment of the invention, L is at least a distance separated from the center frequency point of the frequency spectrum of the first sub-frequency domain signal by half a symbol rate, N is an integer greater than zero and smaller than N, and N is Nfft-L-1。
In this embodiment, L is a fixed value, where N is a first possible implementation of LfftNumber of points in time-frequency transformation, RsIs the symbol rate, fsIs the sampling rate. If 2 times the sampling rate is taken as an example, i.e. fs＝2RsThen, it can be calculated that L is 0.75Nfft. Alternatively, L is a fixed value L ═ L1+ M, M being an integer greater than zero.
In this embodiment, a second possible implementation of L, L ═ L1+ M, M may take different values, M may take the value [0, Nfft-n-L]Or M may be greater than Nfft-n-L. When the value of M is larger than Nfftn-L, then FXI*(n+L1+M)＝FXI*(n+L1+M-Nfft) I.e. for the n + L1And performing cyclic shift on the + M frequency points. In the embodiment of the present invention, how many different values M take, that is, the number of values of M, may be selected according to the requirement on the accuracy of the delay estimation, and if the requirement on the accuracy of the delay estimation is higher, the number of values of M is greater, that is, M may be more multivalued. If the requirement on the accuracy of the delay estimation is low, the number of values of M is small, and a person skilled in the art needs to determine according to actual conditions, which is not limited in the embodiment of the present invention. Wherein L is1The calculation method of (a) is the same as the first possible implementation method of L, and details are not repeated.
In the embodiment of the present invention, the delay estimator 303 obtains the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the n + L frequency point, and there are various implementation manners, which will be illustrated below.
A. The first implementation mode comprises the following steps:
l is a fixed value, i.e. L ═ L1Or L ═ L1+ M, M is an integer. The first implementation is described below.
In the first implementation manner, the delay estimator 303 multiplies the frequency component of the first sub-frequency domain signal at the nth frequency point by the conjugate of the frequency component at the n + L frequency point to obtain the first signal component, i.e. the first signal component
AXI＝FXI(n)·FXI*(n+L) (1)
The delay estimator 303 multiplies the frequency component of the first sub-frequency domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point to obtain the second signal component, i.e., the frequency component at the n frequency point
BXI＝FXI(n+L)·FXI*(n) (2)
If the phase angle of the first sub-frequency domain signal at the nth frequency point is the complex conjugate of the phase angle at the n + L frequency point, the real part is unchanged, and the imaginary part is inverted, that is, the phase is opposite, then a in expression (1) isXIThe conjugate multiplication of the frequency point n and the frequency point n + L may be understood as to multiply the amplitude of the first sub-frequency domain signal at the nth frequency point and the phase of the first sub-frequency domain signal at the n + L frequency point, so as to obtain a first phase angle of the in-phase component, where the phase angle is a phase angle obtained by subtracting the phases of the first sub-frequency domain signal at the nth frequency point and the n + L frequency point, and it may be understood that the interval L between the nth frequency point and the n + L frequency point is a distance between a central frequency point of the frequency spectrum of the first sub-frequency domain signal and a frequency point at a position spaced by half a symbol rate on the negative frequency spectrum, specifically referring to fig. 4, where the frequency point n shown in fig. 4.
B in expression (2)XIThe conjugate multiplication of the first sub-frequency domain signal is understood to be amplitude multiplication of the first sub-frequency domain signal at the n + L frequency point and the nth frequency point, and phase subtraction of the first sub-frequency domain signal at the n + L frequency point and the nth frequency point is performed to obtain a first phase angle of the in-phase component, where the phase angle is a phase difference between the first sub-frequency domain signal at the n + L frequency point and the nth frequency point, and it can be understood that L between the n + L frequency point and the nth frequency point is a distance between a central frequency point of a frequency spectrum of the first sub-frequency domain signal and a frequency point at a position where a positive frequency spectrum is spaced by half a symbol rate.
In a first implementation manner, if the first signal component is a conjugate multiplication of a frequency component of the first sub-frequency-domain signal at the (n + L) th frequency point and a frequency component at the nth frequency point, then L between the (n + L) th frequency point and the nth frequency point is a distance between a central frequency point of a frequency spectrum of the first sub-frequency-domain signal and a frequency point at a position spaced by half a symbol rate from the positive frequency spectrum. The second sub-signal component is a conjugate multiplication of the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point, and then, L between the nth frequency point and the (n + L) th frequency point is a distance between the center frequency point of the frequency spectrum of the first sub-frequency domain signal and the frequency point spaced by half a symbol rate on the negative frequency spectrum.
The calculation of the first signal component and the second signal component may be selected according to actual needs, as long as the interval between two frequency points for calculating the first signal component and the interval between two frequency points for calculating the second signal component are ensured to be the interval of one symbol rate between the positive frequency spectrum and the negative frequency spectrum of the first sub-frequency domain signal.
As can be seen from the above example, the delay estimator 303 can extract the first phase angle of the in-phase component by using the first signal component and the second signal component, and the extracted phase angles are different only in sign, so that the probability of accurately extracting the phase angles is increased, and the accuracy of the delay estimation is improved.
For the processes of acquiring the third signal component and the fourth signal component of the second sub-frequency domain signal, the first signal component and the second signal component are the same, and are not described in detail herein.
B. The second implementation mode comprises the following steps:
in the first implementation, the delay estimator 303 only performs conjugate multiplication on frequency components of a pair of frequency points, for example, the nth frequency point and the (n + L) th frequency point. In a specific implementation process, since the phase angles of the first sub-frequency domain signals at different frequency points may be different, in order to reduce an error of the first phase angle for extracting the in-phase component, on the basis of the first implementation manner, the delay estimator 303 traverses N from 1 to N, that is, performs conjugate multiplication on the frequency components of the frequency points by N to obtain N first sub-signal components, adds the N first sub-signal components to obtain the first signal component and N second sub-signal components, and adds the N second sub-signal components to obtain the second signal component. The frequency components of the N pairs of frequency points are subjected to conjugate multiplication, and N first sub-signal components and N second sub-signal components are obtained and added, that is, the phase differences of the N pairs of frequency points are added and then averaged, so that the accuracy of extracting the first phase angle of the in-phase component according to the first signal component and the second signal component is improved, and the purpose of improving the accuracy of delay estimation is further achieved.
In this embodiment of the present invention, the delay estimator 303 traverses N from 1 to N, may traverse N from small to large, may traverse N from large to small, may traverse N from middle to both sides, or traverse N in other manners, which is not limited in this embodiment of the present invention.
For the acquisition process of the third signal component and the fourth signal component of the second sub-frequency domain signal and the technical effect that can be achieved, the description of the first signal component and the second signal component is omitted.
C. The third implementation mode comprises the following steps:
l is equal to L1+ M, M may take different values.
In the following, two different values of M are exemplified, for example, M ═ 1 and M ═ 2. When M is equal to 1, the delay estimator 303 sums the frequency component of the first sub-frequency-domain signal at the nth frequency point with the frequency component at the n + L th frequency point1Conjugate multiplication of frequency components at +1 frequency points to obtain a first signal component to be at the n + L th frequency point1Multiplying the frequency component at each frequency point by the conjugate of the frequency component at the (n + 1) th frequency point to obtain a second signal component; when M is 2, the delay estimator 303 sums the frequency component of the first sub-frequency-domain signal at the nth frequency point with the frequency component at the n + L th frequency point1Conjugate multiplication of frequency components at +2 frequency points to obtain a first signal component to be at the n + L th frequency point1The frequency components at the frequency points are multiplied by the conjugates of the frequency components at the n +2 th frequency points to obtain second signal components, and thus, two first signal components and two second signal components are obtained in total.
For the processes of acquiring the third signal component and the fourth signal component of the second sub-frequency domain signal, the first signal component and the second signal component are the same, and are not described in detail herein.
In the embodiment of the present invention, in the second implementation, the delay estimator 303 adds N first sub-signal components to obtain a first signal component and adds N second sub-signal components to obtain a second signal component during the traversal of N, which is to reduce the error of extracting the phase difference between different frequency points of the first sub-frequency domain signal to improve the accuracy of extracting the first phase angle of the in-phase component and further improve the delay estimation accuracy, and in the third implementation, when M takes different values, a plurality of different first signal components, a plurality of different second signal components, a plurality of different third signal components, and a plurality of different fourth signal components can be obtained, and further, the plurality of different first signal components, the plurality of different second signal components, the plurality of different third signal components, and the plurality of different fourth signal components can be utilized, and obtaining a plurality of different phase differences of the in-phase component and the orthogonal component, and further processing the plurality of different phase differences to reduce an error of obtaining the phase difference between the in-phase component and the orthogonal component, namely improving the accuracy of delay estimation from the other dimension.
D. The fourth implementation mode comprises the following steps:
l, M are of the same value as in the third implementation.
Continuing with the example where M takes two different values, for example, M-1 and M-2. When M is equal to 1, the delay estimator 303 traverses N from 1 to N, and sums the frequency component of the first sub-frequency-domain signal at the nth frequency point with the frequency component at the N + L th frequency point1Multiplying the conjugate of the frequency components at +1 frequency points to obtain N first sub-signal components, adding the N first sub-signal components to obtain a first signal component, and multiplying the N first sub-signal components at the N + L th frequency point to obtain a second signal component1The frequency components at the frequency points are multiplied by the conjugate of the frequency components at the (N + 1) th frequency point to obtain N second sub-signal components, and the N second sub-signal components are added to obtain a second signal component. When M is 2, the delay estimator 303 traverses N from 1 to N, and sums the frequency component of the first sub-frequency-domain signal at the nth frequency point with the frequency component at the N + L th frequency point1Conjugate multiplication of frequency components at +2 frequency points to obtain a first signal component to be at the n + L th frequency point1Frequency component at each frequency point and frequency component at n +2The conjugates of the frequency components at the frequency points are multiplied to obtain N second sub-signal components, which are added to obtain the second signal components, thus obtaining two first signal components and two second signal components in total.
For the processes of acquiring the third signal component and the fourth signal component of the second sub-frequency domain signal, the first signal component and the second signal component are the same, and are not described in detail herein.
In the embodiment of the present invention, the delay estimator 303 adds the N first sub-signal components to obtain a first signal component, and adds the N second sub-signal components to obtain a second signal component during the traversal of N; adding the N third sub-signal components to obtain a third signal component, adding the N fourth sub-signal components to obtain a fourth signal component, which reduces errors in extracting phase differences between different frequency points of the first sub-frequency domain signal and extracting phase differences between different frequency points of the second sub-frequency domain signal, thereby improving accuracy in extracting a first phase angle of an in-phase component and a second phase angle of an orthogonal component, and further improving delay estimation accuracy, further, when M takes different values, a plurality of different first signal components, a plurality of different second signal components, a plurality of different third signal components and a plurality of different fourth signal components can be obtained, and a plurality of phase differences between the in-phase component and the orthogonal component can be obtained by using the plurality of different first signal components, the plurality of different second signal components, the plurality of different third signal components and the plurality of different fourth signal components, and further processing a plurality of different phase differences to reduce the error of obtaining the phase difference between the in-phase component and the quadrature component, and further improving the accuracy of the delay estimation from the other dimension.
In the embodiment of the present invention, after the delay estimator 303 acquires the first signal component and the second signal component, the phase angle of the in-phase component can be obtained according to the first signal component and the second signal component, and the phase angle of the in-phase component is referred to as a first phase angle, which is expressed as, for example, if the first signal component is the second signal component, the first phase angle is the first phase angle
When the values of M are different, the delay estimator 303 obtains a plurality of first signal components and a plurality of second signal components of the first sub-frequency domain signal, and further obtains a plurality of first phase angles of the in-phase component by using the first signal components and the second signal components corresponding to the same M in the plurality of first signal components and the plurality of second signal components. Wherein, the first signal component and the second signal component corresponding to the same M mean that when M takes the first value, the frequency component of the first sub-frequency domain signal at the nth frequency point and the sum of the frequency components at the n + L th frequency point are utilized1The frequency components at + M frequency points obtain signal components. For example, continuing with the example where M takes two different values, M-1 and M-2. When M is 1, the delay estimator 303 obtains the first signal component of the first sub-frequency-domain signal and obtains the second signal component of the first sub-frequency-domain signal, and when M is 2, the delay estimator 303 obtains the first signal component of the first sub-frequency-domain signal and obtains the second signal component of the first sub-frequency-domain signal, and then the sum is the first signal component and the second signal component corresponding to the same M, and the sum is the first signal component and the second signal component corresponding to the same M. The delay estimator 303 thus obtains the first phase angle of the in-phase component using the first signal component and the second signal component and obtains the first phase angle of the in-phase component using the first signal component and the second signal component
In the embodiment of the present invention, after the delay estimator 303 acquires the third signal component and the fourth signal component, the phase angle of the orthogonal component can be obtained according to the third signal component and the fourth signal component, and the phase angle of the orthogonal component is referred to as a second phase angle and is denoted as a second phase angle
When the value of M is different, the delay estimator 303 obtains a plurality of third signal components and a plurality of fourth signal components of the second sub-frequency domain signal, and further obtains a plurality of second phase angles of the orthogonal component by using the third signal components and the fourth signal components corresponding to the same M in the plurality of third signal components and the plurality of fourth signal components. For example, continuing with the example where M takes two different values, M-1 and M-2. When M is 1, the delay estimator 303 obtains the second phase angle of the orthogonal component when M is 2, and the delay estimator 303 obtains the second phase angle of the orthogonal component
In the embodiment of the present invention, after the delay estimator 303 obtains the plurality of first signal components, the plurality of second signal components, the plurality of third signal components, and the plurality of fourth signal components, a plurality of first phase angles and a plurality of second phase angles are obtained accordingly, a plurality of phase differences are obtained according to the first phase angle and the second phase angle corresponding to the same M in the plurality of first phase angles and the plurality of second phase angles, and it is continued to take two different values as an example, where M is 1 and M is 2. When M is 1, the delay estimator 303 obtains the phase difference between the in-phase component and the quadrature component, and when M is 2, the delay estimator 303 obtains the phase difference between the in-phase component and the quadrature component, and then calculates an average phase difference between the two phase differences, and takes the average phase difference as the phase difference between the quadrature component and the quadrature component, that is, performs filtering processing on the obtained plurality of phase differences by a filter. And filtering the plurality of phase differences to reduce an error of obtaining the phase difference between the in-phase component and the quadrature component, thereby improving the accuracy of the delay estimation.
In the embodiment of the present invention, after the delay estimator 303 obtains the phase difference between the in-phase component and the quadrature component, the delay T between the in-phase component and the quadrature component may also be calculated according to the phase difference, where f is the frequency of the received optical signal. After the delay time T is calculated, the received optical signal is compensated by the delay time T in the following.
And a delay compensator 304 for performing delay compensation on the optical signal using the phase difference.
In the embodiment of the present invention, the obtained delay T may be used in the frequency domain to perform phase adjustment on the frequency domain signals fxi (n) and fxq (n) so as to achieve the purpose of performing delay compensation on the received optical signal, or the received optical signal may also be subjected to delay compensation in the time domain, which will be described below.
In the first implementation manner of the embodiment of the present invention, the delay compensator 304 may be a phase shifter, and the phase shifter adjusts the phase of the first sub-frequency domain signal FXI or the second sub-frequency domain signal FXQ according to the phase difference between the in-phase component and the quadrature component, so as to achieve the purpose of performing delay compensation on the received optical signal.
In the second implementation manner of the embodiment of the present invention, the delay compensator 304 may also be a clock, and the clock adjusts the delay of the analog-to-digital converter in the analog signal processor 301 by using the delay T calculated by the delay estimator, so as to achieve the purpose of performing delay compensation on the received optical signal. Alternatively, the delay compensator 304 uses the delay T to apply the quantized signal x through a delay circuitiOr xqDelay adjustment for delay compensation of received optical signals, e.g. by quantized signal xiFor example, the input signal to the delay circuit is xi(T-T), after the adjustment of the delay circuit, outputting x from the delay circuiti(t), the output signal xiAnd (t) is the signal after orthogonal delay compensation.
Referring to fig. 5, a method for estimating delay according to an embodiment of the present invention can be implemented by a delay estimator, where the delay estimator is a part of an optical receiver, and a flow of the method is described as follows:
step 501: the time delay estimator receives a frequency domain signal which is obtained by performing time-frequency transformation processing on a received optical signal by an optical receiver;
step 502: the time delay estimator acquires a first sub-frequency domain signal of an in-phase component of the optical signal and a second sub-frequency domain signal of an orthogonal component of the optical signal according to the frequency domain signal;
step 503: and the time delay estimator calculates the phase difference between the in-phase component and the orthogonal component according to the first sub-frequency domain signal and the second sub-frequency domain signal, and the phase difference between the in-phase component and the orthogonal component is used for the optical receiver to carry out time delay estimation on the optical signal.
In the embodiment of the present invention, the methods provided in steps 501 to 503 have been introduced in the description of the delay estimator provided in the embodiment shown in fig. 3, and are not described herein again.
Referring to fig. 6, an embodiment of the present invention provides a delay estimator, which includes a network interface 601 and a processor 602 connected to the same bus 600.
The processor 602 may be a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), one or more Integrated circuits for controlling program execution, a baseband chip, or the like.
The network interface 601 may be connected to the processor 602 via the bus 600 (as shown in fig. 6, for example), or may be connected to the processor via a dedicated connection line, respectively.
The delay estimator may also include a memory, which may be coupled to the processor 602 via the bus 600. The number of the memories may be one or more, and the memories may be Read Only Memories (ROMs), Random Access Memories (RAMs), or magnetic disk memories, etc.
By programming the processor 602, the code corresponding to the aforementioned delay estimation method is solidified into a chip, so that the chip can execute the delay estimation method provided by the foregoing embodiment shown in fig. 5 when running, and how to program the processor 602 is a technique known by those skilled in the art, and is not described here again.
Referring to fig. 7, an embodiment of the present invention provides a delay estimator, which includes a receiving module 701, an obtaining module 702, and a calculating module 703.
In practical applications, entity devices corresponding to the obtaining module 702 and the calculating module 703 may be integrated in the processor 602 in fig. 6, and entity devices corresponding to the receiving module 701 may be integrated in the network interface 601 in fig. 6.
The embodiment of the invention provides an optical receiver, in the optical receiver, a time delay estimator obtains a frequency domain signal, a first sub-frequency domain signal of an in-phase component of an optical signal received by the optical receiver and a second sub-frequency domain signal of an orthogonal component of the optical signal are obtained according to the frequency domain signal, and then a phase difference of the in-phase component and the orthogonal component is calculated according to the first sub-frequency domain signal and the second sub-frequency domain signal, so that a time delay compensator performs time delay compensation on the received optical signal by using the phase difference.
The above embodiments are only used to describe the technical solutions of the embodiments of the present invention in detail, but the above description of the embodiments is only used to help understanding the method and the core idea of the embodiments of the present invention, and should not be construed as limiting the present application. Those skilled in the art can easily conceive of changes or substitutions within the technical scope of the embodiments of the present invention, and all such changes or substitutions are intended to be included within the scope of the embodiments of the present invention.

Claims (19)

  1. An optical receiver, comprising:
    the analog signal processor is used for carrying out photoelectric conversion processing on the received optical signal to obtain an electric signal;
    the digital signal processor is used for carrying out time-frequency transformation processing on the electric signal to obtain a frequency domain signal;
    the time delay estimator is used for acquiring a first sub-frequency domain signal of an in-phase component of the optical signal and a second sub-frequency domain signal of a quadrature component of the optical signal according to the frequency domain signals, and calculating a phase difference of the in-phase component and the quadrature component according to the first sub-frequency domain signal and the second sub-frequency domain signal;
    and the delay compensator is used for carrying out delay compensation on the optical signal by utilizing the phase difference.
  2. The optical receiver of claim 1, wherein the delay estimator, when calculating the phase difference of the in-phase component and the quadrature component from the first sub-frequency domain signal and the second sub-frequency domain signal, is specifically configured to:
    obtaining a first signal component and a second signal component according to the first sub-frequency domain signal; wherein the first signal component and the second signal component are used to extract a first phase angle of the in-phase component;
    obtaining a third signal component and a fourth signal component according to the second sub-frequency domain signal; wherein the third signal component and the fourth signal component are used to extract a second phase angle of the quadrature component;
    calculating a phase difference between the in-phase component and the quadrature component from the first signal component, the second signal component, the third signal component, and the fourth signal component.
  3. The optical receiver of claim 2, wherein the delay estimator, when obtaining the first signal component and the second signal component from the first sub-frequency domain signal, is specifically configured to:
    obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point;
    the delay estimator, when obtaining a third signal component and a fourth signal component according to the second sub-frequency domain signal, is specifically configured to:
    obtaining the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point;
    wherein, L is at least a distance separated by half symbol rate from the center frequency point of the frequency spectrum of the first sub-frequency domain signal or a distance separated by half symbol rate from the center frequency point of the frequency spectrum of the second sub-frequency domain signal, N is an integer larger than zero and smaller than N, and N is equal to the frequency point number of the time frequency conversion minus L plus 1.
  4. The optical receiver of claim 3, wherein N isfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsIs the sampling rate;
    the delay estimator is specifically configured to, when obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point:
    multiplying the frequency component of the first sub-frequency domain signal at the nth frequency point by the conjugate of the frequency component at the (n + L) th frequency point to obtain the first signal component;
    multiplying the frequency component of the first sub-frequency domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point to obtain the second signal component.
  5. The optical receiver according to claim 4, wherein the delay estimator multiplies the frequency component of the first sub-frequency-domain signal at the nth frequency point by the conjugate of the frequency component at the n + L frequency point to obtain the first signal component, and is specifically configured to:
    traversing N from 1 to N to obtain N first sub-signal components;
    adding the N first sub-signal components to obtain the first signal component;
    the delay estimator is configured to, when the second signal component is obtained by multiplying the frequency component of the first sub-frequency-domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point, specifically:
    traversing N from 1 to N to obtain N second sub-signal components;
    and adding the N second sub-signal components to obtain the second signal component.
  6. An optical receiver as claimed in claim 3, characterized in that L equals L1+ M, wherein, NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsM is an integer greater than zero for the sampling rate;
    the delay estimator is specifically configured to, when obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point:
    for each value of M, the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the n + L1Conjugate multiplication of frequency components at + M frequency points to obtain the first signal component, and obtain a plurality of first signal components in total;
    for each value of M, the first sub-frequency domain signal is positioned at the n + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the n + M frequency points to obtain the second signal components, and obtaining a plurality of second signal components;
    the delay estimator is specifically configured to, when obtaining the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point:
    for each value of M, the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the n + L1Conjugate multiplication of frequency components at + M frequency points to obtain the third signal component, and obtain a plurality of third signal components in total;
    for each value of M, the second sub-frequency domain signal is positioned at the n + L1And multiplying the frequency components at the frequency points by the conjugates of the frequency components at the n + M frequency points to obtain the fourth signal components, and obtaining a plurality of fourth signal components in total.
  7. An optical receiver as claimed in claim 3, characterized in that L equals L1+ M, wherein, NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsM is an integer greater than zero for the sampling rate;
    the delay estimator is specifically configured to, when obtaining the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point:
    for the first value of M, traversing N from 1 to N, and comparing the frequency component of the first sub-frequency domain signal at the nth frequency point with the frequency component at the N + L1Conjugate multiplication of frequency components at + M frequency points to obtain N first sub-signal components; adding the N first sub-signal components to obtain the first signal component; the first value is any one value of M;
    for the first value of M, traversing N from 1 to N, and carrying out signal transmission on the first sub-frequency domainNumber n + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the N + M frequency points to obtain N second sub-signal components; adding the N second sub-signal components to obtain the second signal component;
    for a plurality of values of M, obtaining a plurality of first signal components and a plurality of second signal components;
    the delay estimator is specifically configured to, when obtaining the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point:
    for the first value of M, N is traversed from 1 to N, and the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the N + L1Multiplying the conjugates of the frequency components at + M frequency points to obtain N third sub-signal components, and adding the N third sub-signal components to obtain the third signal component;
    for the first value of M, traversing N from 1 to N, and enabling the second sub-frequency domain signal to be at the N + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the N + M frequency points to obtain N fourth sub-signal components, and adding the N fourth sub-signal components to obtain the fourth signal component;
    for a plurality of values of M, a plurality of third signal components and a plurality of fourth signal components are obtained.
  8. The optical receiver according to claim 6 or 7, wherein the delay estimator, when calculating the phase difference between the in-phase component and the quadrature component based on the first signal component, the second signal component, the third signal component and the fourth signal component, is specifically configured to:
    obtaining a plurality of first phase angles of the in-phase component from first and second signal components corresponding to the same M of the plurality of first and second signal components, and obtaining a plurality of second phase angles of the quadrature component from third and fourth signal components corresponding to the same M of the plurality of third and fourth signal components;
    subtracting a first phase angle and a second phase angle which correspond to the same M in the plurality of first phase angles and the plurality of second phase angles to obtain a plurality of phase differences;
    calculating an average phase difference of the plurality of phase differences, and determining the average phase difference as the phase difference of the in-phase component and the quadrature component.
  9. The optical receiver of claim 1, wherein the delay compensator, when performing delay compensation on the optical signal using the phase difference, is specifically configured to:
    and adjusting the phase of the first sub-frequency domain signal or the second sub-frequency domain signal by using the phase difference to complete the delay compensation of the optical signal.
  10. The optical receiver of claim 1, wherein the delay compensator, when performing delay compensation on the optical signal using the phase difference, is specifically configured to:
    and adjusting the time delay of an analog-to-digital converter in the analog signal processor by using the time delay obtained by the time delay estimator according to the phase difference so as to complete the time delay compensation of the optical signal.
  11. A method of delay estimation, comprising:
    the time delay estimator receives a frequency domain signal which is obtained by performing time-frequency transformation processing on a received optical signal by an optical receiver;
    the time delay estimator acquires a first sub-frequency domain signal of an in-phase component of the optical signal and a second sub-frequency domain signal of a quadrature component of the optical signal according to the frequency domain signal;
    and the delay estimator calculates the phase difference between the in-phase component and the orthogonal component according to the first sub-frequency domain signal and the second sub-frequency domain signal, and the phase difference between the in-phase component and the orthogonal component is used for the optical receiver to carry out delay estimation on the optical signal.
  12. The method of claim 11, wherein the delay estimator calculates a phase difference of the in-phase component and the quadrature component from the first sub-frequency domain signal and the second sub-frequency domain signal, comprising:
    the time delay estimator obtains a first signal component and a second signal component according to the first sub-frequency domain signal; wherein the first signal component and the second signal component are used to extract a first phase angle of the in-phase component;
    the time delay estimator obtains a third signal component and a fourth signal component according to the second sub-frequency domain signal; wherein the third signal component and the fourth signal component are used to extract a second phase angle of the quadrature component;
    the delay estimator calculates a phase difference between the in-phase component and the quadrature component from the first signal component, the second signal component, the third signal component, and the fourth signal component.
  13. The method of claim 12, wherein the delay estimator obtains a first signal component and a second signal component from the first sub-frequency domain signal, comprising:
    the time delay estimator obtains the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point;
    the time delay estimator obtains a third signal component and a fourth signal component according to the second sub-frequency domain signal, and includes:
    the time delay estimator obtains the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point;
    wherein, L is at least a distance separated by half symbol rate from the center frequency point of the frequency spectrum of the first sub-frequency domain signal or a distance separated by half symbol rate from the center frequency point of the frequency spectrum of the second sub-frequency domain signal, N is an integer greater than zero and less than N, and N is equal to the frequency point number of the time-frequency transformation minus L plus 1.
  14. The method of claim 13, wherein N isfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsIs the sampling rate;
    the obtaining, by the delay estimator, the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point includes:
    the time delay estimator multiplies the frequency component of the first sub-frequency domain signal at the nth frequency point by the conjugate of the frequency component at the (n + L) th frequency point to obtain the first signal component;
    the delay estimator multiplies the frequency component of the first sub-frequency domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point to obtain the second signal component.
  15. The method of claim 14, wherein the delay estimator multiplies the frequency component of the first sub-frequency-domain signal at the nth frequency bin with the conjugate of the frequency component at the n + L frequency bin to obtain the first signal component, comprising:
    the time delay estimator traverses N from 1 to N to obtain N first sub-signal components;
    the delay estimator adds the N first sub-signal components to obtain the first signal component;
    the delay estimator multiplies the frequency component of the first sub-frequency-domain signal at the n + L frequency point by the conjugate of the frequency component at the n frequency point to obtain the second signal component, and includes:
    the time delay estimator traverses N from 1 to N to obtain N second sub-signal components;
    the delay estimator adds the N second sub-signal components to obtain the second signal component.
  16. The method of claim 13, wherein L is equal to L1+ M, wherein, NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsM is an integer greater than zero for the sampling rate;
    the obtaining, by the delay estimator, the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point includes:
    the time delay estimator compares the frequency component of the first sub-frequency domain signal at the nth frequency point with the frequency component at the n + L th frequency point for each value of M1Conjugate multiplication of frequency components at + M frequency points to obtain the first signal component, and obtain a plurality of first signal components in total;
    the time delay estimator takes the first sub-frequency domain signal at the n + L th position for each value of M1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the n + M frequency points to obtain the second signal components, and obtaining a plurality of second signal components;
    the obtaining, by the delay estimator, the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point includes:
    the time delay estimator compares the frequency component of the second sub-frequency domain signal at the nth frequency point with the frequency component at the n + L th frequency point for each value of M1Conjugate multiplication of frequency components at + M frequency points to obtain the third signal component, and obtain a plurality of third signal components in total;
    the time delay estimator takes the second sub-frequency domain signal at the n + L th position for each value of M1And multiplying the frequency components at the frequency points by the conjugates of the frequency components at the n + M frequency points to obtain the fourth signal components, and obtaining a plurality of fourth signal components in total.
  17. The method of claim 13, wherein L is equal to L1+ M, wherein, NfftIs the number of points, R, of the time-frequency transformationsIs the symbol rate, fsM is an integer greater than zero for the sampling rate;
    the obtaining, by the delay estimator, the first signal component and the second signal component according to the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point includes:
    for a first value of M, the delay estimator traverses N from 1 to N, and sums the frequency component of the first sub-frequency domain signal at the nth frequency point and the frequency component at the N + L1Conjugate multiplication of frequency components at + M frequency points to obtain N first sub-signal components; adding the N first sub-signal components to obtain the first signal component; the first value is any one value of M;
    for a first value of M, the delay estimator traverses N from 1 to N, and the first sub-frequency domain signal is positioned at the N + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the N + M frequency points to obtain N second sub-signal components; adding the N second sub-signal components to obtain the second signal component;
    the delay estimator obtains a plurality of first signal components and a plurality of second signal components for a plurality of values of M;
    the obtaining, by the delay estimator, the third signal component and the fourth signal component according to the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the (n + L) th frequency point includes:
    for the first value of M, the delay estimator traverses from 1 to N, and the frequency component of the second sub-frequency domain signal at the nth frequency point and the frequency component at the N + L1Conjugate multiplication of frequency components at + M frequency points to obtain N third sub-signal components, and adding the N third sub-signal components to obtain the third signal components;
    the delay estimator traverses from 1 to the first value of MTo N, the second sub-frequency domain signal is at the N + L1Multiplying the frequency components at the frequency points by the conjugates of the frequency components at the N + M frequency points to obtain N fourth sub-signal components, and adding the N fourth sub-signal components to obtain the fourth signal component;
    for a plurality of values of M, a plurality of third signal components and a plurality of fourth signal components are obtained.
  18. The method of claim 16 or 17, wherein the delay estimator calculates a phase difference of the in-phase component and the quadrature component from the first signal component, the second signal component, the third signal component, and the fourth signal component, comprising:
    the delay estimator obtains a plurality of first phase angles of the in-phase component according to a first signal component and a second signal component corresponding to the same M in the plurality of first signal components and the plurality of second signal components, and obtains a plurality of second phase angles of the quadrature component according to a third signal component and a fourth signal component corresponding to the same M in the plurality of third signal components and the plurality of fourth signal components;
    the delay estimator calculates the phase difference between the in-phase component and the orthogonal component according to the plurality of first phase angles and the plurality of second phase angles;
    the delay estimator subtracts a first phase angle and a second phase angle which correspond to the same M in the plurality of first phase angles and the plurality of second phase angles to obtain a plurality of phase differences;
    and the time delay estimator calculates the average phase difference of the phase differences and determines the average phase difference as the phase difference of the in-phase component and the orthogonal component.
  19. The method of claim 18, wherein the method further comprises:
    and the time delay estimator obtains the time delay between the in-phase component and the orthogonal component according to the phase difference, wherein the time delay is used for the optical receiver to carry out time delay compensation on the optical signal.
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