CN114362832B - Analog coherent optical communication receiving method and device for realizing differential detection in electric domain - Google Patents
Analog coherent optical communication receiving method and device for realizing differential detection in electric domain Download PDFInfo
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Abstract
The application discloses a method and a device for receiving analog coherent optical communication for realizing differential detection in an electric domain, and relates to the field of coherent optical communication; equalizing the demodulated electric domain complex signal based on the analog equalizer to obtain an equalized electric domain complex signal; performing delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals; and detecting the differential coherent signal and correcting the residual phase offset to obtain an NRZ signal and receiving the NRZ signal. The application can bypass the optical phase-locked loop or the electric signal phase-locked loop, can ensure the linear characteristic of the photoelectric conversion of the signal and is convenient for dispersion compensation.
Description
Technical Field
The application relates to the field of coherent optical communication, in particular to a method and a device for receiving analog coherent optical communication for realizing differential detection in an electric domain.
Background
A commercially available coherent optical communication technology is actually a combination of coherent optical communication and digital signal processing (Digital Signal Process, abbreviated as DSP). Whereas digital signal processing generally consists of: dispersion compensation-clock sampling error extraction-adaptive equalization (polarization demultiplexing and polarization mode dispersion compensation are completed) -carrier recovery (frequency difference estimation and compensation) -carrier recovery (phase noise estimation and compensation) -symbol decision-differential decoding. The digital coherent optical communication technology is widely used for 100G, 400G and 800G optical communication systems, and plays a dominant role in the construction of long distance networks and metropolitan area networks.
With the rise of internet enterprises, data communication among data centers grows exponentially, and the existing digital coherent optical communication technology is high in cost and power consumption, so that huge electricity charge consumption cost and heat dissipation requirements are brought. Meanwhile, because the distance between the data centers is relatively short, the traditional alignment and alignment detection technology is widely adopted for interconnection. But for data center interconnection requirements of 80km or more, coherent optical communication techniques are required.
The main energy consumption of the existing coherent optical communication comes from analog-to-digital conversion and digital signal processing, so that the power consumption of an optical module can be greatly reduced by changing a digital signal processing part into analog signal processing or optical signal processing, and the requirement of developing green economy is met.
One of the conventional analog coherent optical communication is a phase-locked loop technology, in which, as shown in fig. 1, after a signal is subjected to eigen-optical demodulation, the phase of a demodulated signal is detected, and the eigen-laser frequency is feedback-adjusted to make the eigen-laser and the phase of a received optical signal consistent, the optical signal is demodulated into an NRZ electrical signal, and then the NRZ (Non Return Zero Code, non-return-to-zero code) signal is received by an electrical signal receiver; the second is an electric phase-locked loop technique, as shown in fig. 2, i.e. the intrinsic laser is operated in free-running oscillation, and the demodulated electrical signal is locked by an adjustable electrical frequency source. The two technologies have the common problem that the phase-locked loop bandwidth is narrow due to delay caused by phase detection, loop filtering and circuit routing, and the fast frequency difference change of the receiving and transmitting end laser is difficult to track.
The third is delay differential detection, as shown in fig. 3, namely, delay signal light one symbol, two adjacent signal light symbols are coherent, and the method is that the front and rear symbols are emitted by one light source and are not affected by the frequency difference of the laser source, but the coherent detection method cannot use the amplification effect of intrinsic laser, has very low detection sensitivity to unamplified signal light, and the delay coherent detection is equivalent to conjugate multiplication of the front and rear signals, so that the conversion from an optical domain to an electric domain (analog domain) is nonlinear, and dispersion is difficult to be effectively compensated.
Disclosure of Invention
Aiming at the defects existing in the prior art, the application aims to provide the analog coherent optical communication receiving method and the device for realizing differential detection in an electric domain, which can bypass an optical phase-locked loop or an electric signal phase-locked loop, can ensure the linear characteristic of signal photoelectric conversion and are convenient for dispersion compensation.
In order to achieve the above object, the present application provides a method for receiving analog coherent optical communication for implementing differential detection in an electrical domain, which specifically includes the following steps:
differential encoding is carried out on the optical signals at a transmitting end, and demodulation is carried out on the optical signals at a receiving end to obtain electric domain complex signals;
equalizing the demodulated electric domain complex signal based on the analog equalizer to obtain an equalized electric domain complex signal;
performing delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals;
and detecting the differential coherent signal and correcting the residual phase offset to obtain an NRZ signal and receiving the NRZ signal.
Based on the above technical solution, the demodulation of the optical signal at the receiving end to obtain the electrical domain complex signal specifically includes: and demodulating the optical signal by adopting an intrinsic laser in a free oscillation state at a receiving end to obtain an electric domain complex signal.
On the basis of the technical scheme, the optical signal is differentially encoded at the transmitting end, wherein the differential encoding method for modulating the data signal at the transmitting end comprises the following steps:
wherein TX (n) represents an X-polarized modulated data signal subjected to differential encoding, TY (n) represents a Y-polarized modulated data signal subjected to differential encoding, n represents a symbol sequence number, SX (n) represents a source signal of X polarization at a transmitting end, SY (n) represents a source signal of Y polarization at the transmitting end, j represents a complex unit, pi represents a circumference ratio, exp represents an exponential function with a natural constant e as a base;
modulating the differentially encoded optical signal using the modulated data signal at the transmitting end, the representation of the two polarized optical signals being:
Signal_X(t)＝TX(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Signal_Y(t)＝TY(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Wherein Signal_X (t) represents an X-polarized light Signal, signal_Y (t) represents a Y-polarized light Signal, and f c The carrier optical frequency is represented, and t represents time.
Based on the technical scheme, the analog equalizer is a 2×2 multi-tap complex signal equalizer.
Based on the technical scheme, the analog equalizer equalizes the demodulated electric domain complex signal to obtain the equalized electric domain complex signal, and the specific implementation mode is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,x-path equalized electric domain complex signal representing analog equalizer output,/for>Represents the Y-path equalized electrical domain complex signal output by the analog equalizer, Δf represents the frequency difference, Δf=f c -f L ，f c Representing the carrier optical frequency, f L Represents the eigen frequency, phi X Representing the phase difference of X polarization, phi Y Representing the phase difference of the Y polarization, T represents the symbol period and T represents time.
On the basis of the technical scheme, the balanced electric domain complex signals are subjected to delay coherent processing to obtain differential coherent signals, and the specific mode for carrying out delay coherent processing is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,representation pair->Differential coherent signal obtained after delay coherent processing, < >>Representation pair->Differential coherent signals obtained by performing delay coherent processing, and conj represents conjugation.
On the basis of the technical scheme, the obtained NRZ signal is received based on the electric signal receiver.
On the basis of the technical scheme, the differential coherent signal is detected and the residual phase offset is corrected, wherein the specific mode for correcting the residual phase offset is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,representation pair->NRZ signal obtained after correction of residual phase bias,/->Representation pair->And (5) correcting the NRZ signal obtained after the residual phase bias.
The application provides an analog coherent optical communication receiving device for realizing differential detection in an electric domain, which comprises the following components:
the processing module is used for carrying out differential coding on the optical signals at the transmitting end and demodulating the optical signals at the receiving end to obtain electric domain complex signals;
the equalization module is used for equalizing the demodulated electric domain complex signals based on the analog equalizer to obtain equalized electric domain complex signals;
the execution module is used for carrying out delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals;
and the receiving module is used for detecting the differential coherent signal and correcting the residual phase offset, obtaining an NRZ signal and receiving the NRZ signal.
On the basis of the technical proposal, the method comprises the following steps,
the processing module demodulates the optical signal by adopting an intrinsic laser in a free oscillation state at a receiving end to obtain an electric domain complex signal;
the receiving module receives the obtained NRZ signal based on an electrical signal receiver.
Compared with the prior art, the application has the advantages that: the optical signal is differentially encoded at a transmitting end, the optical signal is demodulated into an electric domain complex signal by an intrinsic laser working in a free oscillation state at a receiving end, the electric domain complex signal is equalized by an analog equalizer to obtain an equalized electric domain complex signal, then the equalized electric domain complex signal is subjected to delay coherent processing to obtain a differential coherent signal, finally the differential coherent signal is detected and the residual phase offset is corrected to obtain an NRZ signal and received, thereby bypassing an optical phase-locked loop or an electric signal phase-locked loop, ensuring the linear characteristic of the photoelectric conversion of the signal and facilitating dispersion compensation.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of coherent light reception based on an optical phase-locked loop in the present application;
FIG. 2 is a schematic diagram of coherent light reception based on an electric phase-locked loop in the present application;
FIG. 3 is a schematic diagram of coherent light reception based on delay coherence in the present application;
FIG. 4 is a flow chart of a method for receiving analog coherent optical communication for implementing differential detection in an electrical domain according to an embodiment of the present application;
fig. 5 is a schematic diagram illustrating a specific implementation of a method for receiving analog coherent optical communication according to an embodiment of the present application.
Detailed Description
The embodiment of the application provides an analog coherent optical communication receiving method for realizing differential detection in an electric domain, which is characterized in that an optical signal is differentially encoded at a transmitting end, the optical signal is demodulated into an electric domain complex signal by an intrinsic laser working in a free oscillation state at a receiving end, the electric domain complex signal is equalized by an analog equalizer to obtain an equalized electric domain complex signal, then the equalized electric domain complex signal is subjected to delay coherent processing to obtain a differential coherent signal, finally the differential coherent signal is detected and residual phase offset is corrected to obtain an NRZ signal and received, thereby bypassing an optical phase-locked loop or an electric signal phase-locked loop, ensuring the linear characteristic of signal photoelectric conversion and facilitating dispersion compensation. The embodiment of the application correspondingly provides an analog coherent optical communication receiving device for realizing differential detection in an electric domain.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application.
Referring to fig. 4, an analog coherent optical communication receiving method for implementing differential detection in an electric domain is provided in an embodiment of the present application, which is used for performing signal receiving processing of a coherent optical communication system in an analog domain (electric domain), using intrinsic light to demodulate a light signal, then performing equalization in the electric domain to compensate for chromatic dispersion, performing polarization demultiplexing on the signal, and then delaying coherence in the electric domain. The method specifically comprises the following steps:
s1: differential encoding is carried out on the optical signals at a transmitting end, and demodulation is carried out on the optical signals at a receiving end to obtain electric domain complex signals; in the embodiment of the application, an optical signal is demodulated at a receiving end to obtain an electric domain complex signal, which is specifically: and demodulating the optical signal by adopting an intrinsic laser in a free oscillation state at a receiving end to obtain an electric domain complex signal.
For differential encoding of an optical signal at a transmitting end in the present application, a specific encoding mode is:
the binary expression of the values of the source signals (SX (n) and SY (n)) with two bits, SXn () and SY (n), can be 00, 01, 10 and 11, and the binary expression corresponds to 0, 1, 2 and 3 of decimal, and the differential coding method of the transmitting end modulation data signal is as follows:
wherein TX (n) represents an X-polarized modulated data signal subjected to differential encoding, TY (n) represents a Y-polarized modulated data signal subjected to differential encoding, n represents a symbol sequence number, SX (n) represents a source signal of X-polarization at a transmitting end, SY (n) represents a source signal of Y-polarization at a transmitting end, j represents a complex unit, pi represents a circumference ratio, exp represents an exponential function based on a natural constant e.
The complex numbers can be used for representing four values of TX (n) and TY (n), namely 1+j, -1-j and 1-j, and the initial value TX (0)/TY (0) can be arbitrarily taken in the four values. For example, when n is 0, TX (0) =ty (0) =1+j.
The modulated data signal is used at the transmitting end to modulate a differentially encoded optical signal, the two polarized optical signals being representable as:
Signal_X(t)＝TX(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Signal_Y(t)＝TY(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Wherein Signal_X (t) represents an X-polarized light Signal, signal_Y (t) represents a Y-polarized light Signal, and f c The carrier optical frequency is represented, and t represents time.
S2: and (3) carrying out equalization on the demodulated electric domain complex signals based on the analog equalizer to obtain equalized electric domain complex signals.
In the present application, the analog equalizer is a 2×2 multi-tap complex signal equalizer. Because the electric domain complex signal is the linear movement of the optical signal, the multi-tap complex signal equalizer can not only complete polarization demultiplexing, but also compensate dispersion. The analog equalized output signal has eliminated inter-code crosstalk such as chromatic dispersion, filtering effect, etc.
In the embodiment of the application, the electric domain complex signal obtained by demodulation is balanced based on the analog equalizer, and the obtained balanced electric domain complex signal can be expressed as:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,x-path equalized electric domain complex signal representing analog equalizer output,/for>Represents the Y-path equalized electrical domain complex signal output by the analog equalizer, Δf represents the frequency difference, Δf=f c -f L Representing the frequency difference, f c For the carrier optical frequency, f L Is the eigen frequency, phi X Representing the phase difference of X polarization, phi Y Representing the phase difference of the Y polarization, T represents the symbol period and T represents time.
S3: and carrying out delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals. In the application, delay coherent processing is carried out on the balanced electric domain complex signal to obtain a differential coherent signal, wherein the specific mode of carrying out the delay coherent processing is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,representation pair->Differential coherent signal obtained after delay coherent processing, < >>Representation pair->Differential coherent signals obtained by performing delay coherent processing, and conj represents conjugation.
S4: and detecting the differential coherent signal and correcting the residual phase offset to obtain an NRZ signal and receiving the NRZ signal, and particularly, receiving the obtained NRZ signal based on an electric signal receiver.
In the embodiment of the application, the differential coherent signal is detected and the residual phase deviation is corrected, wherein the specific mode for correcting the residual phase deviation is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,representation pair->NRZ signal obtained after correction of residual phase bias,/->Representation pair->And (5) correcting the NRZ signal obtained after the residual phase bias.
When the differential coherent signal is multiplied by exp (-j 2 pi delta fT), four result values of 1, j, -1 and j are obtained, and the complex signal has three values of-1, 0 and 1 no matter the real signal and the imaginary signal, so that the final judgment is inconvenient.
In the present application, the term "a" is used to refer to, and />The two analog signals are composed of two analog signals.
The following describes a specific description of an analog coherent optical communication receiving method according to an embodiment of the present application with reference to fig. 5.
Differential encoding is carried out on the optical signal at a transmitting end, the optical signal is demodulated by adopting an intrinsic laser with free oscillation at a receiving end, and the electric domain complex signal obtained by demodulation is balanced based on an analog equalizer to obtain and /> Through detection and delay coherent treatment, the +.>Then pair->Correcting residual phase deviation, namely performing phase correction to obtain an NRZ signal, and finally receiving the obtained NRZ signal by adopting an electric signal receiver; />Through detection and delay coherent treatment, the +.>Then pair->And correcting the residual phase offset, namely performing phase correction to obtain an NRZ signal, and finally receiving the obtained NRZ signal by adopting an electric signal receiver.
According to the analog coherent optical communication receiving method for realizing differential detection in the electric domain, an optical signal is differentially encoded at a transmitting end, the optical signal is demodulated into an electric domain complex signal by an intrinsic laser working in a free oscillation state at a receiving end, the electric domain complex signal is balanced by an analog equalizer to obtain an equalized electric domain complex signal, then the equalized electric domain complex signal is subjected to delay coherent processing to obtain a differential coherent signal, finally the differential coherent signal is detected, residual phase offset is corrected to obtain an NRZ signal and received, and therefore an optical phase-locked loop or an electric signal phase-locked loop is bypassed, the linear characteristic of signal photoelectric conversion can be ensured, and dispersion compensation is facilitated.
The embodiment of the application provides an analog coherent optical communication receiving device for realizing differential detection in an electric domain, which comprises a processing module, an equalization module, an execution module and a receiving module.
The processing module is used for carrying out differential coding on the optical signals at the transmitting end and demodulating the optical signals at the receiving end to obtain electric domain complex signals; the equalization module is used for equalizing the demodulated electric domain complex signal based on the analog equalizer to obtain an equalized electric domain complex signal; the execution module is used for carrying out delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals; the receiving module is used for detecting the differential coherent signal and correcting the residual phase offset, and obtaining and receiving the NRZ signal.
In the embodiment of the application, the processing module demodulates the optical signal by adopting an intrinsic laser in a free oscillation state at the receiving end; the reception module receives the obtained NRZ signal based on the electric signal receiver. Because the electric domain signal is the linear movement of the optical signal, the multi-tap complex signal equalizer can not only complete polarization demultiplexing, but also compensate dispersion. The analog equalized output signal has eliminated inter-code crosstalk such as chromatic dispersion, filtering effect, etc.
In the embodiment of the application, the optical signal is differentially encoded at the transmitting end, wherein the differential encoding method for modulating the data signal at the transmitting end comprises the following steps:
wherein TX (n) represents an X-polarized modulated data signal subjected to differential encoding, TY (n) represents a Y-polarized modulated data signal subjected to differential encoding, n represents a symbol sequence number, SX (n) represents a source signal of X-polarization at a transmitting end, SY (n) represents a source signal of Y-polarization at a transmitting end, j represents a complex unit, pi represents a circumference ratio, exp represents an exponential function based on a natural constant e.
In the embodiment of the application, the electric domain complex signals obtained by demodulation are balanced based on an analog equalizer, and the electric domain complex signals after equalization are obtained by the specific implementation modes:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,x-path equalized electric domain complex signal representing analog equalizer output,/for>Represents the Y-path equalized electrical domain complex signal output by the analog equalizer, Δf represents the frequency difference, Δf=f c -f L ，f c Representing the carrier optical frequency, f L Represents the eigen frequency, phi X Representing the phase difference of X polarization, phi Y Representing the phase difference of the Y polarization, T represents the symbol period and T represents time.
In the embodiment of the application, delay coherent processing is carried out on the balanced electric domain complex signals to obtain differential coherent signals, wherein the specific mode of carrying out delay coherent processing is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,representation pair->Differential coherent signal obtained after delay coherent processing, < >>Representation pair->Differential coherent signals obtained by performing delay coherent processing, and conj represents conjugation.
In the embodiment of the application, the differential coherent signal is detected and the residual phase deviation is corrected, wherein the specific mode for correcting the residual phase deviation is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,representation pair->NRZ signal obtained after correction of residual phase bias,/->Representation pair->And (5) correcting the NRZ signal obtained after the residual phase bias.
According to the analog coherent optical communication receiving device for realizing differential detection in the electric domain, an optical signal is differentially encoded at a transmitting end, the optical signal is demodulated into an electric domain complex signal by an intrinsic laser working in a free oscillation state at a receiving end, the electric domain complex signal is balanced by an analog equalizer to obtain an equalized electric domain complex signal, then the equalized electric domain complex signal is subjected to delay coherent processing to obtain a differential coherent signal, finally the differential coherent signal is detected, residual phase offset is corrected to obtain an NRZ signal and received, and therefore an optical phase-locked loop or an electric signal phase-locked loop is bypassed, the linear characteristic of signal photoelectric conversion can be ensured, and dispersion compensation is facilitated.
In the description of the present application, it should be noted that the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, and are merely for convenience of describing the present application and simplifying the description, and are not indicative or implying that the apparatus or element in question must have a specific azimuth, be constructed and operated in a specific azimuth, and thus should not be construed as limiting the present application. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and "coupled" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
It should be noted that in the present application, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (6)
1. The analog coherent optical communication receiving method for realizing differential detection in an electric domain is characterized by comprising the following steps:
differential encoding is carried out on the optical signals at a transmitting end, and demodulation is carried out on the optical signals at a receiving end to obtain electric domain complex signals;
equalizing the demodulated electric domain complex signal based on the analog equalizer to obtain an equalized electric domain complex signal;
performing delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals;
detecting the differential coherent signal and correcting the residual phase bias to obtain an NRZ signal and receiving the NRZ signal;
the differential coding method for modulating the data signal at the transmitting end comprises the following steps:
wherein TX (n) represents an X-polarized modulated data signal subjected to differential encoding, TY (n) represents a Y-polarized modulated data signal subjected to differential encoding, n represents a symbol sequence number, SX (n) represents a source signal of X polarization at a transmitting end, SY (n) represents a source signal of Y polarization at the transmitting end, j represents a complex unit, pi represents a circumference ratio, exp represents an exponential function with a natural constant e as a base;
modulating the differentially encoded optical signal using the modulated data signal at the transmitting end, the representation of the two polarized optical signals being:
Signal_X(t)＝TX(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Signal_Y(t)＝TY(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Wherein Signal_X (t) represents an X-polarized light Signal, signal_Y (t) represents a Y-polarized light Signal, and f c Representing the carrier optical frequency, t representing time;
the analog equalizer is used for equalizing the demodulated electric domain complex signal to obtain an equalized electric domain complex signal, and the specific implementation mode is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,x-path equalized electric domain complex signal representing analog equalizer output,/for>Represents the Y-path equalized electrical domain complex signal output by the analog equalizer, Δf represents the frequency difference, Δf=f c -f L ，f c Representing the carrier optical frequency, f L Represents the eigen frequency, phi X Representing the phase difference of X polarization, phi Y Representing the phase difference of the Y polarization, T represents the symbol period, and T represents time;
the specific way of carrying out delay coherent processing on the balanced electric domain complex signal is as follows:
wherein ,representation pair->Differential coherent signal obtained after delay coherent processing, < >>Representation pairDifferential coherent signals obtained after delay coherent processing are subjected to conj representing conjugation;
the specific method for detecting the differential coherent signal and correcting the residual phase offset is as follows:
wherein ,representation pair->NRZ signal obtained after correction of residual phase bias,/->Representation pairAnd (5) correcting the NRZ signal obtained after the residual phase bias.
2. The method for receiving analog coherent optical communication for implementing differential detection in an electrical domain according to claim 1, wherein the demodulation of the optical signal at the receiving end to obtain an electrical domain complex signal comprises: and demodulating the optical signal by adopting an intrinsic laser in a free oscillation state at a receiving end to obtain an electric domain complex signal.
3. The analog coherent optical communication receiving method for implementing differential detection in an electrical domain according to claim 1, wherein: the analog equalizer is a 2×2 multi-tap complex signal equalizer.
4. An analog coherent optical communication reception method for implementing differential detection in an electric domain according to claim 1, wherein the obtained NRZ signal is received based on an electric signal receiver.
5. An analog coherent optical communication receiving apparatus for implementing differential detection in an electric domain, comprising:
the processing module is used for carrying out differential coding on the optical signals at the transmitting end and demodulating the optical signals at the receiving end to obtain electric domain complex signals;
the equalization module is used for equalizing the demodulated electric domain complex signals based on the analog equalizer to obtain equalized electric domain complex signals;
the execution module is used for carrying out delay coherent processing on the balanced electric domain complex signals to obtain differential coherent signals;
the receiving module is used for detecting the differential coherent signal and correcting the residual phase bias to obtain an NRZ signal and receiving the NRZ signal;
the differential coding method for modulating the data signal at the transmitting end comprises the following steps:
wherein TX (n) represents an X-polarized modulated data signal subjected to differential encoding, TY (n) represents a Y-polarized modulated data signal subjected to differential encoding, n represents a symbol sequence number, SX (n) represents a source signal of X polarization at a transmitting end, SY (n) represents a source signal of Y polarization at the transmitting end, j represents a complex unit, pi represents a circumference ratio, exp represents an exponential function with a natural constant e as a base;
modulating the differentially encoded optical signal using the modulated data signal at the transmitting end, the representation of the two polarized optical signals being:
Signal_X(t)＝TX(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Signal_Y(t)＝TY(n)exp(j2πf c t), when nT is less than or equal to t < (n+1) t
Wherein Signal_X (t) represents an X-polarized light Signal, signal_Y (t) represents a Y-polarized light Signal, and f c Representing the carrier optical frequency, t representing time;
the analog equalizer is used for equalizing the demodulated electric domain complex signal to obtain an equalized electric domain complex signal, and the specific implementation mode is as follows:
when nT is less than or equal to t < (n+1) t
When nT is less than or equal to t < (n+1) t
wherein ,x-path equalized electric domain complex signal representing analog equalizer output,/for>Represents the Y-path equalized electrical domain complex signal output by the analog equalizer, Δf represents the frequency difference, Δf=f c -f L ，f c Representing the carrier optical frequency, f L Represents the eigen frequency, phi X Representing the phase difference of X polarization, phi Y Representing the phase difference of the Y polarization, T represents the symbol period, and T represents time;
the specific way of carrying out delay coherent processing on the balanced electric domain complex signal is as follows:
wherein ,representation pair->Differential coherent signal obtained after delay coherent processing, < >>Representation pairDifferential coherent signals obtained after delay coherent processing are subjected to conj representing conjugation;
the specific method for detecting the differential coherent signal and correcting the residual phase offset is as follows:
wherein ,representation pair->NRZ signal obtained after correction of residual phase bias,/->Representation pairAnd (5) correcting the NRZ signal obtained after the residual phase bias.
6. An analog coherent optical communication receiver apparatus for implementing differential detection in an electrical domain as defined in claim 5, wherein:
the processing module demodulates the optical signal by adopting an intrinsic laser in a free oscillation state at a receiving end to obtain an electric domain complex signal;
the receiving module receives the obtained NRZ signal based on an electrical signal receiver.
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