CN114244436A - Adaptive matched filtering system of bandwidth variable light signal and matching method thereof - Google Patents

Adaptive matched filtering system of bandwidth variable light signal and matching method thereof Download PDF

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CN114244436A
CN114244436A CN202111548149.XA CN202111548149A CN114244436A CN 114244436 A CN114244436 A CN 114244436A CN 202111548149 A CN202111548149 A CN 202111548149A CN 114244436 A CN114244436 A CN 114244436A
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CN114244436B (en
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苏玉龙
汪伟
朱江峰
谢小平
高铎瑞
白兆峰
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Xidian University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/118—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum specially adapted for satellite communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
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    • H04B10/5161—Combination of different modulation schemes
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Abstract

The invention provides a self-adaptive matched filtering system of a bandwidth variable light signal and a matching method thereof, wherein the bandwidth variable light signal sequentially passes through a three-terminal interface unit, the bandwidth value of the light signal is obtained by measurement and calculation, and the signal of the three-terminal interface unit enters a filtering regulation and control unit to carry out bandwidth matched filtering; the invention can be adaptive to optical signals with different bandwidths, and does not need to occupy other channel resources to inform the bandwidth value of the current optical signal; the matching filtering of optical signals with different bandwidths can be met, the size of the bandwidth of the reflection spectrum filtering can be flexibly adjusted by changing the temperature, the bandwidth matching with the input optical signal is achieved, in addition, the matching error caused by echo noise in an optical path can be further accurately adjusted through spectrum monitoring at the output end, and the compatibility of various modulation modes is realized.

Description

Adaptive matched filtering system of bandwidth variable light signal and matching method thereof
Technical Field
The invention relates to the field of high-speed optical transmission, in particular to a matching filtering system and a matching method of an optical signal.
Background
Space Laser Communication (Space Laser Communication) refers to a technology for transmitting digital information in Space by using a Laser beam as a carrier, such as information of voice, image, video and the like, and is an effective means for realizing large-capacity long-distance transmission in the Space field at present. The carrier frequency range of the space laser communication is 190 THz-560 THz, and is 4-5 orders of magnitude higher than the conventional microwave S, X, Ka wave band, so that the transmission of large-capacity data is easier to realize. At present, the transmission rate of the optical communication test links between the satellites at home and abroad reaches Gbps magnitude, and dozens of Gbps or even hundreds of Gbps magnitude can be reached in the future through the wavelength division multiplexing technology. At present, high-bandwidth instruments required by satellites, such as a hyper-spectral imager, a Synthetic Aperture Radar (SAR) and the like, and future interplanetary manned spaceflight need to complete real-time video communication, which means that transmission of a large number of high-resolution high-definition images and video information is imperative. In order to meet the requirement of large-capacity long-distance transmission, a plurality of engineering projects for space laser communication have been developed in europe and the united states, for example, the transmission rate of the european laser communication relay system EDRS high-orbit satellite to the low-orbit satellite is 1.8Gbps, the american laser communication relay system LCRD is planned to realize high-orbit-to-ground communication, the transmission rate thereof is 2.44Gbps, and the communication rate of the american TBIRD is planned to reach 200Gbps, so that the large-capacity long-distance space laser communication is in the future.
At present, the space laser communication can be applied to communication in different application scenes such as low rail-low rail, low rail-high rail, high rail-ground and the like, and the communication distance of the space laser communication varies from thousands to tens of thousands of kilometers. However, in practical engineering applications, due to the influence of channels and on-track working conditions, interference will be caused to the stability of link communication, and therefore, in order to ensure reliable and feasible link, the system needs to have the capability of flexibly switching communication rate, that is, when the link is interfered, the bandwidth of a transmission signal is reduced, so that the receiving sensitivity is improved, and this needs to have the capability of matched filtering on an optical signal with variable bandwidth to ensure that the link has sufficient redundancy, and an adaptive filtering method for realizing the optical signal with variable bandwidth is not seen yet.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an adaptive matched filtering system of a bandwidth variable optical signal and a matching method thereof. The invention aims to overcome the problem that the prior art is difficult to solve the problem of adaptive matched filtering of optical signals with variable bandwidth, innovatively provides an adaptive matched filtering method of optical signals with variable bandwidth, obviously improves the communication performance of a space communication link under various interferences, and provides reliable guarantee for long-distance and large-capacity communication of space.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a self-adaptive matched filtering system of a bandwidth variable light signal comprises a three-terminal interface unit and a filtering regulation and control unit; the bandwidth variable light signal sequentially passes through the three-terminal interface unit, the bandwidth value of the light signal is obtained through measurement and calculation, and the signal of the three-terminal interface unit enters the filtering regulation and control unit to be subjected to bandwidth matching filtering;
the three-terminal interface unit comprises an optical isolator a, an optical isolator b, an optical splitter a, an optical splitter b, an optical circulator, a spectrum monitoring module a and a spectrum monitoring module b, wherein the optical isolator a is connected with a port 1 of the optical splitter a, a port 2 of the optical splitter a is connected with a port 1 of the optical circulator, a port 3 of the optical splitter a is connected with the spectrum monitoring module a, a port 3 of the optical circulator is connected with a port 1 of the optical splitter b, a port 2 of the optical splitter b is connected with the optical isolator b, and a port 3 of the optical splitter b is connected with the spectrum monitoring module b;
the filtering regulation and control unit comprises an optical filter a, a TEC refrigeration piece a, an optical filter b, a TEC refrigeration piece b, an anti-reflection termination module and a temperature tuning control module, wherein an output port (2 ports of the optical circulator) of the three-port interface unit is connected with the optical filter a, the optical filter a is connected with the optical filter b, the optical filter b is connected with the anti-reflection termination module, the TEC refrigeration piece a is connected with the optical filter a, the TEC refrigeration piece b is connected with the optical filter b, a port 1 of the temperature tuning control module is connected with the TEC refrigeration piece a, a port 2 of the temperature tuning control module is connected with the TEC refrigeration piece b, a port 3 of the temperature tuning control module is connected with a spectrum monitoring module b in the three-port interface unit, and a port 4 of the temperature tuning control module is connected with the spectrum monitoring module a;
the 3dB bandwidth of the bandwidth-variable optical signal is f1(GHz)～f2(GHz) random variation with 1 ≤ f1≤100，1≤f2≤100，f1≤f2(ii) a The bandwidth of the bandwidth-variable optical signal is changed into a slowly-changing characteristic; .
The bandwidth-variable optical signal is one of an intensity optical signal (OOK), a phase optical signal (BPSK), and a high-order modulated optical signal (QPSK, 16QAM, 64 QAM).
The optical filter is a fiber grating filter or a multilayer dielectric film filter;
the spectrum monitoring module is of a grating type structure or a Fourier transform type structure;
the anti-reflection termination module is a plane optical fiber end face grinding module or an inclined octave optical fiber end face grinding module.
In the three-terminal interface unit, a bandwidth-variable optical signal enters a port 1 of an optical splitter a after passing through an optical isolator a, the optical splitter a divides the optical signal into two parts, one part enters a spectrum monitoring module a, and the other part enters a port 1 of an optical circulator and is output from a port 2 to enter a filtering regulation and control unit; in the filtering regulation and control unit, an optical signal reflects and transmits the whole signal containing noise after passing through an optical filter a, the reflected light returns to an optical circulator port 2, the transmitted light enters an optical filter b and still reflects and transmits, the reflected light returns according to the original path, the transmitted light is accessed into an anti-reflection termination module to prevent echo reflection caused by uneven section of an optical fiber, and all signals reflected to the optical circulator port 2 are output through an optical circulator port 3; the spectrum monitoring module b monitors the spectrum wavelength of the optical circulator port 3, the spectrum monitoring module a and the spectrum monitoring module b control the TEC refrigerating plate a and the TEC refrigerating plate b through the temperature tuning control module, the temperature enables the central wavelength of the optical filter to move left to enable the wavelength to be smaller or to move right to enable the wavelength to be larger, the dynamic adjustment control of the filtering bandwidth is achieved, and the filtering bandwidth is matched with the optical signal bandwidth.
The invention also provides a matching method of the adaptive matching filtering system of the bandwidth variable light signal, which specifically comprises the following steps:
(1) as shown in FIG. 1, the center wavelength of the bandwidth-variable optical signal is λsHaving a bandwidth of DeltaLambdasThe bandwidth is variable, and the optical signal enters a spectrum monitoring module a through a signal on a port 3 of the optical splitter a, a 3dB bandwidth value of the optical signal is obtained through measurement and calculation, and a signal on a port 2 of the optical splitter a enters a filtering regulation and control unit through an optical circulator to carry out bandwidth matching filtering;
(2) the filter bandwidths of the optical filter a and the optical filter b are respectively delta lambdaaAnd Δ λbCentral wavelength is respectively lambdaaAnd λb(ii) a The central wavelengths of the optical filter a and the optical filter b are shifted left or right along with the temperature change, so that the filtering bandwidth formed by combining the two filters is correspondingly increased or decreased; according to the test data of the central wavelength of the optical filter changing with the temperature, the central wavelength of the optical filter a and the temperature T are fitted1Curve function λ ofa(T1) Fitting the center wavelength and temperature T of the optical filter b2Curve function λ ofb(T2)；
(3) Measuring the central wavelength lambda of the current input optical signal according to the step (1)sAnd spectral bandwidth Δ λsNumerical values as input conditions, in combination with a curve function lambdaa(T1) And a curve function lambdab(T2) In order to achieve a center wavelength and a spectral bandwidth that coincide with the input optical signal, the temperature T required for the optical filter a required at that time is calculated1Temperature T required for sum optical filter b2；
(4) Respectively carrying out temperature tuning control on the TEC refrigeration piece a and the TEC refrigeration piece b to ensure that the temperature of the optical filter a reaches T1The temperature of the optical filter b reaches T2。
(5) Monitoring whether the central wavelength of the filtered optical signal is consistent with the central wavelength of the bandwidth-variable optical signal in real time through a spectrum monitoring module b, monitoring whether the spectral bandwidth of the filtered optical signal is consistent with the spectral bandwidth of the bandwidth-variable optical signal in real time, and if so, not adjusting the temperature of the optical filter a and the optical filter b; if the difference values are not consistent, calculating a difference value of central wavelengths measured by the spectrum monitoring module a (the 3-port signal of the optical splitter a) and the spectrum monitoring module b (the 3-port signal of the optical splitter b), and a difference value of spectral bandwidths of the spectrum monitoring module a (the 3-port signal of the optical splitter a) and the spectrum monitoring module b (the 3-port signal of the optical splitter b), and continuously adjusting temperature values of the optical filter a and the optical filter b according to the difference values when the central wavelengths and the spectral bandwidths are compared, wherein the deviation signal is the deviation of the spectral bandwidths of the input optical signal and the output optical signal;
(6) if the bandwidth of the optical signal is variable, the bandwidth of the optical signal is Delta lambdasWhen the temperature changes, the temperature tuning control module calculates new T1And T2Adjusting the temperature T of the optical filter a and the optical filter b respectively in real time1And T2Therefore, the filtering bandwidth of the input optical signal is always consistent with the spectral bandwidth of the input optical signal in the dynamic change process, and matched filtering is realized.
The invention has the beneficial effects that:
(1) optical signals of different bandwidths can be adapted. Due to the adoption of the spectrum monitoring function, the 3dB bandwidth value of the input optical signal can be easily measured and calculated by methods such as grating reflection or Fourier transform, and other channel resources do not need to be occupied to inform the bandwidth value of the current optical signal.
(2) The matched filtering of optical signals with different bandwidths can be met. Compared with the traditional single fixed bandwidth optical filter, the method adopts the cascade optical filter to realize the combined reflection spectrum filtering, can flexibly adjust the size of the reflection spectrum filtering bandwidth by changing the temperature to match with the bandwidth of an input optical signal, can further accurately adjust the matching error caused by echo noise in an optical path by spectrum monitoring at an output end, and does not have the public report at home and abroad at present.
(3) And compatibility of various modulation systems can be realized. The method adopts a reflective filtering method in an optical domain, does not need to know the modulation format of the optical signal, only needs to measure the spectral bandwidth of the optical signal, and therefore, can be suitable for various modulation systems, such as OOK, BPSK, QPSK, 16QAM and the like.
Drawings
FIG. 1 is a schematic diagram of the principles of the present invention;
FIG. 2 is a schematic diagram of filter bandwidths in different combination configurations; fig. 2(a) is a schematic diagram of the filter bandwidth of the combination configuration 1, fig. 2(b) is a schematic diagram of the filter bandwidth of the combination configuration 2, and fig. 2(c) is a schematic diagram of the filter bandwidth of the combination configuration 3.
Fig. 3 is an eye diagram of the output optical signal under the conditions of the matched bandwidth filtering and the non-matched bandwidth filtering, where (a) of fig. 3 is an eye diagram of the optical signal output with the filtering bandwidth smaller than the bandwidth of the optical signal, where (b) of fig. 3 is an eye diagram of the optical signal output with the filtering bandwidth equal to the bandwidth of the optical signal, and where (c) of fig. 3 is an eye diagram of the optical signal output with the filtering bandwidth larger than the bandwidth of the optical signal.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
The technical principle of the invention is as follows:
1. space high-speed optical communication principle
The spatial high-speed optical communication process mainly comprises transmitting, transmitting and receiving. In the transmission process, high-speed optical communication is firstly generated, and is usually realized by using a mach-zehnder modulator (MZM), and the transmission function of the MZM is as follows:
Figure BDA0003416298850000051
in the formula (1), Eout(t) and Ein(t) input and output light fields, V, of the modulator, respectivelyπThe half-wave voltage for modulation is determined by the material of the modulator. Vin(t) is the high speed signal voltage applied to the modulator, VbiasIs the bias voltage of the modulator.
When V isbias＝Vπ、Vin(t)＝VπWhen (t) · a (t), a (t) ± 1(a (t)) represents the 1 code and 0 code in the pseudo random NRZ code differentially encoded in advance, a high-speed optical signal can be generated. In equation (1), the output optical signal is expressed asThe following:
Figure BDA0003416298850000052
the modulated optical signal is amplified by a high-power optical amplifier and then transmitted by an optical antenna, and the optical signal received at a receiving end has the following expression:
ERX(t)＝A(t)Eout(t) (3)
in the formula (3), ERX(t) represents the optical field of the received optical signal, and A (t) represents the channel time-varying attenuation coefficient.
At the receiving end, the optical filter is used for filtering broadband noise, the optical filter is a spatial phase grating formed in the fiber core of the optical fiber, coupling is generated between the fiber core mode of forward transmission and the fiber core mode of backward transmission through the grating, when a beam of light is transmitted through the Bragg grating, each small section of the optical fiber with the changed refractive index can only reflect the light wave with corresponding specific wavelength, namely the Bragg wavelength, and the light waves with other wavelengths are transmitted continuously, so that the grating forms emission and transmission to incident waves, and the reflection wavelength is the Bragg wavelength:
λB＝2neffΛ (4)
in the formula (4), neffAnd lambda is the equivalent refractive index of the fiber core, and lambda is the period of the fiber grating. The bandwidth of the grating can be calculated according to the following formula:
Figure BDA0003416298850000053
in the formula (5), δ n0Is the cladding to core refractive index difference, and η is the energy fraction in the core. The reflection at the peak wavelength is approximately as follows:
Figure BDA0003416298850000054
in the formula (6), N is the number of grating periods, and N is the refractive index of the fiber core. The reflected wavelength is affected by changes in mechanical and thermal properties. For example, due to the elasto-optic effect, stress variations on the fiber can affect the equivalent refractive index as well as the grating period; due to the thermo-optic effect, the equivalent refractive index is also changed by the temperature drift change, and the influence of thermal expansion and thermal contraction exists, and the relation of the reflection wavelength with the temperature, the elasto-optic coefficient, the thermal expansion coefficient and the thermo-optic coefficient is as follows:
λ'＝λB(1-ρα)Δε+λB(α+ξ)ΔΤ+λB (7)
in formula (7), λ' is the changed reflection wavelength, and ρ α, α, ξ, Δ ∈, Δ Τ are an elasto-optical coefficient, a thermal expansion coefficient, a thermo-optical coefficient, a stress variation amount, and a temperature variation amount, respectively.
When the optical filter is used as a filter element in optical communication, the central wavelength change due to the thermo-optic effect can be considered without considering the elasto-optic effect, and as can be seen from the equation (7), the wavelength shift is in direct proportion to the temperature, and the central wavelengths λ of the optical filter a and the optical filter b areaAnd λbAnd the surface temperature T of the optical filter1And T2Can be expressed as shown in the following formula:
λa＝a1T1 2+b1T1+c1 (8)
λb＝a2T2 2+b2T2+c2 (9)
wherein a1, b1 and c1 are defined by the wavelength lambda of the optical filter aaAs a function of temperature T1And performing quadratic fitting on the result data of the change test to obtain the data. a2, b2 and c2 are controlled by the wavelength λ of optical filter bbAs a function of temperature T2And performing quadratic fitting on the result data of the change test to obtain the data.
The bandwidths of the optical filter a and the optical filter b are respectively Delta lambdaaAnd Δ λb(Δλa＜Δλb) At a fixed value, the temperature T is adjusted according to the required filter bandwidth, as shown in FIG. 21And T2The fit constitutes the matched filter bandwidth Δ λ. The minimum value of Δ λ is Δ λ1The value of the bandwidth minimum in the two optical filters, i.e. the bandwidth Δ λ of the optical filter aaCoincidentally, as shown in fig. 2 (a); the maximum value of Δ λ is Δ λ2Is the bandwidth of the optical filter a Delta lambdaaB bandwidth of sum optical filter delta lambdabAs shown in fig. 2 (b); the bandwidth between the maximum and minimum is Δ λ3The upper wavelength lambda of the filtered spectrum after combination of the two optical filtersUAnd lower wavelength lambdaLThe interval therebetween is shown in fig. 2 (c). Summarizing the above, the following equation is obtained:
Δλ1＝Δλa (10)
Δλ2＝Δλa+Δλb (11)
Figure BDA0003416298850000061
by bringing equations (8) and (9) into equation (12), the combined filter bandwidth Δ λ can be obtained3With a temperature variable T1And T2The relationship of (a) is shown as follows:
Figure BDA0003416298850000071
as can be seen from equation (13), T is changed1And T2Namely, different filtering bandwidths delta lambda can be realized3And thus with the spectral bandwidth of the input optical signal, Δ λsKeeping consistent and realizing optimal matched filtering. In addition, when the spectral bandwidth is kept consistent, the central wavelength lambda of the input optical signal is requiredsIn keeping with the center wavelength λ' of the combined filtered spectrum, the following equation is satisfied:
Figure BDA0003416298850000072
by bringing the formula (8) and the formula (9) into the formula (14), the combined filtered spectrum center wavelength and temperature variation T can be obtained1And T2The relationship of (a) is shown as follows:
Figure BDA0003416298850000073
spectral bandwidth of input optical signal Δ λsAnd a central wavelength lambdasAre all known values that can be tested, so that the temperature T corresponding to the moment is calculated by the known values1And T2. By combining the equations (13) and (15) respectively, the following equations can be obtained:
Δλs-2λs＝-2(a1T1 2+b1T1+c1)+Δλa (16)
Δλs+2λs＝2(a2T2 2+b2T2+c2)+Δλb (17)
t can be obtained by solving the root of the quadratic function in the formula (16) and the formula (17)1And T2The value of (b) is specifically represented by the following formula:
Figure BDA0003416298850000074
Figure BDA0003416298850000075
from the above derivation process, the following is summarized: (1) the central wavelengths of the optical filter a and the optical filter b change along with the temperature, a curve function lambda a (T1) of the central wavelength of the optical filter a and the temperature T1 is fitted, and a curve function lambda b (T2) of the central wavelength of the optical filter b and the temperature T2 is fitted; (2) obtaining the spectral bandwidth DeltaLambda of the input optical signalsAnd a central wavelength lambdasAfter the numerical value is obtained, the temperatures T1 and T2 can be calculated; (3) the surface temperatures of the optical filter a and the optical filter b are respectively up to T1 and T2 through a temperature control means, and the formed filtering spectral bandwidth and the central wavelength of the filtering spectrum are consistent with those of the input optical signal, so that the effect of matched filtering is achieved. As shown in fig. 3(b), when the matched filtering effect is achieved, the eye pattern of the output signal has a large opening degree, the inside of the eye pattern is clean, the variance of the noise at 1 level and 0 level is small, and the likeExcellent characteristics; if the filtering bandwidth is smaller than the optical signal bandwidth, the effective information of the signal is filtered, the rising edge and the falling edge become slow, and the time domain jitter becomes large, as shown in fig. 3 (a); if the filtering bandwidth is larger than the optical signal bandwidth, out-of-band noise will be introduced into the signal, the amplitude noise of the signal will be enhanced, the eyelid will be significantly thickened, and the signal-to-noise ratio will be decreased, as shown in fig. 3 (c).
Example (b):
based on the technical principle, the invention provides an adaptive matched filtering device of variable-bandwidth light signals to realize the optimal receiving of variable-rate signals, namely firstly, the spectral bandwidth and the central wavelength of input light signals are measured and calculated by a spectral monitoring method, and the temperature T required by the light filter a and the light filter b is further calculated according to the data result of the spectral bandwidth and the central wavelength of the input light signals1And T2. The surface temperatures of the optical filter a and the optical filter b are respectively up to T by temperature control means1And T2And the filter spectrum bandwidth and the filter spectrum center wavelength formed at the moment are consistent with those of the input optical signal, so that the effect of matched filtering is achieved.
The feasibility of the invention can be illustrated by the following examples:
a self-adaptive matched filtering system of a bandwidth variable light signal comprises a three-terminal interface unit and a filtering regulation and control unit; the bandwidth variable light signal sequentially passes through the three-terminal interface unit, the bandwidth value of the light signal is obtained through measurement and calculation, and the signal of the three-terminal interface unit enters the filtering regulation and control unit to be subjected to bandwidth matching filtering;
the three-terminal interface unit comprises an optical isolator a, an optical isolator b, an optical splitter a, an optical splitter b, an optical circulator, a spectrum monitoring module a and a spectrum monitoring module b, wherein the optical isolator a is connected with a port 1 of the optical splitter a, a port 2 of the optical splitter a is connected with a port 1 of the optical circulator, a port 3 of the optical splitter a is connected with the spectrum monitoring module a, a port 3 of the optical circulator is connected with a port 1 of the optical splitter b, a port 2 of the optical splitter b is connected with the optical isolator b, and a port 3 of the optical splitter b is connected with the spectrum monitoring module b;
the filtering regulation and control unit comprises an optical filter a, a TEC refrigeration piece a, an optical filter b, a TEC refrigeration piece b, an anti-reflection termination module and a temperature tuning control module, wherein an output port (2 ports of the optical circulator) of the three-port interface unit is connected with the optical filter a, the optical filter a is connected with the optical filter b, the optical filter b is connected with the anti-reflection termination module, the TEC refrigeration piece a is connected with the optical filter a, the TEC refrigeration piece b is connected with the optical filter b, a port 1 of the temperature tuning control module is connected with the TEC refrigeration piece a, a port 2 of the temperature tuning control module is connected with the TEC refrigeration piece b, a port 3 of the temperature tuning control module is connected with a spectrum monitoring module b in the three-port interface unit, and a port 4 of the temperature tuning control module is connected with the spectrum monitoring module a;
the 3dB bandwidth of the bandwidth-variable optical signal randomly changes from f1(GHz) to f2(GHz), wherein f1 is more than or equal to 1 and less than or equal to 100, f2 is more than or equal to 1 and less than or equal to 100, and f2 is more than or equal to f1 and less than or equal to 38; the bandwidth of the bandwidth-variable optical signal is changed into a slowly-changing characteristic; .
The bandwidth-variable optical signal is one of an intensity optical signal (OOK), a phase optical signal (BPSK), and a high-order modulated optical signal (QPSK, 16QAM, 64 QAM).
The optical filter is a fiber grating filter or a multilayer dielectric film filter;
the spectrum monitoring module is of a grating type structure or a Fourier transform type structure;
the anti-reflection termination module is a plane optical fiber end face grinding module or an inclined octave optical fiber end face grinding module.
In the three-terminal interface unit, a bandwidth-variable optical signal enters a port 1 of an optical splitter a after passing through an optical isolator a, the optical splitter a divides the optical signal into two parts, one part enters a spectrum monitoring module a, and the other part enters a port 1 of an optical circulator and is output from a port 2 to enter a filtering regulation and control unit; in the filtering regulation and control unit, an optical signal reflects and transmits the whole signal containing noise after passing through an optical filter a, the reflected light returns to an optical circulator port 2, the transmitted light enters an optical filter b and still reflects and transmits, the reflected light returns according to the original path, the transmitted light is accessed into an anti-reflection termination module to prevent echo reflection caused by uneven section of an optical fiber, and all signals reflected to the optical circulator port 2 are output through an optical circulator port 3; the spectrum monitoring module b monitors the spectrum wavelength of the optical circulator port 3, the spectrum monitoring module a and the spectrum monitoring module b control the TEC refrigerating plate a and the TEC refrigerating plate b through the temperature tuning control module, the temperature enables the central wavelength of the optical filter to move left to enable the wavelength to be smaller or to move right to enable the wavelength to be larger, the dynamic adjustment control of the filtering bandwidth is achieved, and the filtering bandwidth is matched with the optical signal bandwidth.
Referring to the schematic diagram of the present invention shown in fig. 1, a matching method of an adaptive matched filter device for a bandwidth variable optical signal includes the following steps:
(1) after long-distance spatial transmission, the optical signal is input to an adaptive matched filter device, and an optical field expression of the received optical signal can be represented by the following formula:
ERX(t)＝A(t)Eout(t)
(2) broadband noise filtering is performed at the receiving end using an optical filter, as shown in fig. 1. The spectrum monitoring module a can measure the spectral width and the central wavelength of an input optical signal, and the input optical signal enters a filtering regulation and control unit consisting of an optical filter a and an optical filter b after passing through an optical circulator;
(3) wavelength shift in proportion to temperature, center wavelength λ of optical filter a and optical filter baAnd λbAnd the surface temperature T of the optical filter1And T2The relationship (c) can be obtained by a quadratic fit (quadratic fit is more characteristic than a first fit):
λa＝a1T1 2+b1T1+c1
λb＝a2T2 2+b2T2+c2
(4) obtaining the spectral bandwidth DeltaLambda of the input optical signalsAnd a central wavelength lambdasAfter the numerical value is obtained, the temperature T corresponding to the optical filter a and the optical filter b can be calculated1And T2Temperature T1And T2The calculation expression is as follows:
Figure BDA0003416298850000101
Figure BDA0003416298850000102
(5) the temperature tuning control module takes temperature control measures on the TEC refrigerating sheet a and the TEC refrigerating sheet b to enable the surface temperatures of the optical filter a and the optical filter b to reach T respectively1And T2Meanwhile, the spectrum monitoring module b monitors the spectral bandwidth and the central wavelength of the filtered optical signal at the moment, and feeds back the deviation between the spectral bandwidth of the input optical signal and the spectral bandwidth of the output optical signal to the filtering regulation and control unit.
(6) The filtering regulation and control unit further corrects the temperature T1And T2The spectral bandwidth and the central wavelength after filtering are consistent with those of the input optical signal, and the effect of matched filtering is achieved.
Therefore, through the steps, the adaptive matched filtering process of the optical signal with the variable bandwidth is realized.
The embodiment shows that the adaptive matched filtering method for the optical signal with variable bandwidth realizes the bandwidth matched filtering output of the optical signal with variable speed, obviously reduces the noise in the signal, effectively improves the effective signal-to-noise ratio of the signal, provides reliable guarantee for the communication with long space distance and large capacity, and can be widely applied to a space laser communication receiving system.

Claims (8)

1. The utility model provides a bandwidth variable light signal's self-adaptation matched filter system, includes three-terminal interface unit and filtering regulation and control unit, its characterized in that:
the adaptive matched filtering system of the optical signal with variable bandwidth receives the optical signal with variable bandwidth, the optical signal with variable bandwidth sequentially passes through the three-terminal interface unit, the bandwidth value of the optical signal is obtained by measurement and calculation, and the signal of the three-terminal interface unit enters the filtering regulation and control unit to carry out bandwidth matched filtering;
the three-terminal interface unit comprises an optical isolator a, an optical isolator b, an optical splitter a, an optical splitter b, an optical circulator, a spectrum monitoring module a and a spectrum monitoring module b, wherein the optical isolator a is connected with a port 1 of the optical splitter a, a port 2 of the optical splitter a is connected with a port 1 of the optical circulator, a port 3 of the optical splitter a is connected with the spectrum monitoring module a, a port 3 of the optical circulator is connected with a port 1 of the optical splitter b, a port 2 of the optical splitter b is connected with the optical isolator b, and a port 3 of the optical splitter b is connected with the spectrum monitoring module b;
the filtering regulation and control unit comprises an optical filter a, a TEC refrigeration piece a, an optical filter b, a TEC refrigeration piece b, an anti-reflection termination module and a temperature tuning control module, wherein an output port (2 ports of the optical circulator) of the three-port interface unit is connected with the optical filter a, the optical filter a is connected with the optical filter b, the optical filter b is connected with the anti-reflection termination module, the TEC refrigeration piece a is connected with the optical filter a, the TEC refrigeration piece b is connected with the optical filter b, a port 1 of the temperature tuning control module is connected with the TEC refrigeration piece a, a port 2 of the temperature tuning control module is connected with the TEC refrigeration piece b, a port 3 of the temperature tuning control module is connected with a spectrum monitoring module b in the three-port interface unit, and a port 4 of the temperature tuning control module is connected with the spectrum monitoring module a.
2. The system for adaptive matched filtering of a bandwidth variable optical signal according to claim 1, wherein:
the 3dB bandwidth of the bandwidth-variable optical signal is f1(GHz)～f2(GHz) random variation with 1 ≤ f1≤100，1≤f2≤100，f1≤f2(ii) a The bandwidth of the bandwidth variable optical signal changes to a slowly varying characteristic.
3. The system for adaptive matched filtering of a bandwidth variable optical signal according to claim 1, wherein:
the bandwidth-variable optical signal is one of an intensity optical signal OOK, a phase optical signal BPSK, and a high-order modulation optical signal QPSK, 16QAM, and 64 QAM.
4. The system for adaptive matched filtering of a bandwidth variable optical signal according to claim 1, wherein:
the spectrum monitoring module is of a grating type structure or a Fourier transform type structure.
5. The system for adaptive matched filtering of a bandwidth variable optical signal according to claim 1, wherein:
the anti-reflection termination module is a plane optical fiber end face grinding module or an inclined octave optical fiber end face grinding module.
6. The system for adaptive matched filtering of a bandwidth variable optical signal according to claim 1, wherein:
the optical filter is a fiber grating filter or a multilayer dielectric film filter.
7. The system for adaptive matched filtering of a bandwidth variable optical signal according to claim 1, wherein:
in the three-terminal interface unit, a bandwidth-variable optical signal enters a port 1 of an optical splitter a after passing through an optical isolator a, the optical splitter a divides the optical signal into two parts, one part enters a spectrum monitoring module a, and the other part enters a port 1 of an optical circulator and is output from a port 2 to enter a filtering regulation and control unit; in the filtering regulation and control unit, an optical signal reflects and transmits the whole signal containing noise after passing through an optical filter a, the reflected light returns to an optical circulator port 2, the transmitted light enters an optical filter b and still reflects and transmits, the reflected light returns according to the original path, the transmitted light is accessed into an anti-reflection termination module to prevent echo reflection caused by uneven section of an optical fiber, and all signals reflected to the optical circulator port 2 are output through an optical circulator port 3; the spectrum monitoring module b monitors the spectrum wavelength of the optical circulator port 3, the spectrum monitoring module a and the spectrum monitoring module b control the TEC refrigerating plate a and the TEC refrigerating plate b through the temperature tuning control module, the temperature enables the central wavelength of the optical filter to move left to enable the wavelength to be smaller or to move right to enable the wavelength to be larger, the dynamic adjustment control of the filtering bandwidth is achieved, and the filtering bandwidth is matched with the optical signal bandwidth.
8. A matching method using the adaptive matched filter system for optical signals with variable bandwidths of claim 1, comprising the steps of:
(1) the center wavelength of the bandwidth-variable optical signal is lambdasHaving a bandwidth of DeltaLambdasThe bandwidth is variable, and the optical signal enters a spectrum monitoring module a through a signal on a port 3 of the optical splitter a, a 3dB bandwidth value of the optical signal is obtained through measurement and calculation, and a signal on a port 2 of the optical splitter a enters a filtering regulation and control unit through an optical circulator to carry out bandwidth matching filtering;
(2) the filter bandwidths of the optical filter a and the optical filter b are respectively delta lambdaaAnd Δ λbCentral wavelength is respectively lambdaaAnd λb(ii) a The central wavelengths of the optical filter a and the optical filter b are shifted left or right along with the temperature change, so that the filtering bandwidth formed by combining the two filters is correspondingly increased or decreased; according to the test data of the central wavelength of the optical filter changing with the temperature, the central wavelength of the optical filter a and the temperature T are fitted1Curve function λ ofa(T1) Fitting the center wavelength and temperature T of the optical filter b2Curve function λ ofb(T2)；
(3) Measuring the central wavelength lambda of the current input optical signal according to the step (1)sAnd spectral bandwidth Δ λsNumerical values as input conditions, in combination with a curve function lambdaa(T1) And a curve function lambdab(T2) In order to achieve a center wavelength and a spectral bandwidth that coincide with the input optical signal, the temperature T required for the optical filter a required at that time is calculated1Temperature T required for sum optical filter b2；
(4) Respectively carrying out temperature tuning control on the TEC refrigeration piece a and the TEC refrigeration piece b to ensure that the temperature of the optical filter a reaches T1The temperature of the optical filter b reaches T2；
(5) Monitoring whether the central wavelength of the filtered optical signal is consistent with the central wavelength of the bandwidth-variable optical signal in real time through a spectrum monitoring module b, monitoring whether the spectral bandwidth of the filtered optical signal is consistent with the spectral bandwidth of the bandwidth-variable optical signal in real time, and if so, not adjusting the temperature of the optical filter a and the optical filter b; if the difference is not consistent, calculating the difference value of the central wavelengths measured by the spectrum monitoring module a and the spectrum monitoring module b and the difference value of the spectral bandwidths of the spectrum monitoring module a and the spectrum monitoring module b, and continuously adjusting the temperature values of the optical filter a and the optical filter b according to the difference value when the central wavelengths and the spectral bandwidths are compared, wherein the deviation signal is the deviation of the spectral bandwidths of the input optical signal and the output optical signal;
(6) if the bandwidth of the optical signal is variable, the bandwidth of the optical signal is Delta lambdasWhen the temperature changes, the temperature tuning control module calculates new T1And T2Adjusting the temperature T of the optical filter a and the optical filter b respectively in real time1And T2Therefore, the filtering bandwidth of the input optical signal is always consistent with the spectral bandwidth of the input optical signal in the dynamic change process, and matched filtering is realized.
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