CN114244436B - Self-adaptive matched filtering system and matching method for bandwidth-variable optical signals - Google Patents

Self-adaptive matched filtering system and matching method for bandwidth-variable optical signals Download PDF

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CN114244436B
CN114244436B CN202111548149.XA CN202111548149A CN114244436B CN 114244436 B CN114244436 B CN 114244436B CN 202111548149 A CN202111548149 A CN 202111548149A CN 114244436 B CN114244436 B CN 114244436B
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bandwidth
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CN114244436A (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
    • 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
    • H04B10/11—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
    • H04B10/516—Details of coding or modulation
    • H04B10/5161—Combination of different modulation schemes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention provides a self-adaptive matched filtering system and a matching method of a bandwidth-variable optical signal, wherein the bandwidth-variable optical signal sequentially passes through a three-terminal interface unit, the bandwidth value of the optical signal is measured and calculated, 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 adapt to the optical signals with different bandwidths without occupying other channel resources to inform the bandwidth value of the current optical signal; the optical signal matching filter can meet the requirement of matching filtering of optical signals with different bandwidths, the size of the reflection spectrum filtering bandwidth can be flexibly adjusted by changing the temperature, the bandwidth matching of the reflection spectrum filtering bandwidth and the input optical signal can be achieved, in addition, the matching error caused by echo noise in an optical path can be further accurately adjusted through spectrum monitoring at an output end, and the compatibility of various modulation systems can be realized.

Description

Self-adaptive matched filtering system and matching method for bandwidth-variable optical signals
Technical Field
The invention relates to the field of high-speed optical transmission, in particular to a matched filtering system and a matched method for optical signals.
Background
The space laser communication (Space Laser Communication) refers to a technology of transmitting digital information in space by using laser beams as carriers, such as voice, image, video and other information, and is an effective means for realizing large-capacity long-distance transmission in the current space field. The carrier frequency range of the space laser communication is 190 THz-560 THz, which 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 inter-satellite optical communication test link at home and abroad reaches the Gbps level, and the transmission rate can reach tens of Gbps to hundreds of Gbps level in the future through a wavelength division multiplexing technology. The high bandwidth instruments required by the satellites at present, such as hyperspectral imagers, synthetic Aperture Radars (SAR) and the like, and the future interstellar manned aerospace need to complete real-time video communication, which means that a large amount of high-resolution high-definition images and video information transmission is imperative. In order to meet the above requirement of large-capacity long-distance transmission, a plurality of engineering projects of space laser communication have been developed in europe and america, for example, the transmission rate of an EDRS high-orbit satellite to a low-orbit satellite of a european laser communication relay system is 1.8Gbps, an LCRD of a us laser communication relay system is planned to realize high-orbit ground communication, the transmission rate of the LCRD is 2.44Gbps, and the communication rate of a TBIRD plan in the us is up to 200Gbps, so that large-capacity long-distance space laser communication is a trend in the future.
The space laser communication can be applied to different application scene communication 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 kilometers. However, in practical engineering application, because the influence of the channel and the on-orbit working condition will cause interference to the stability of the link communication, in order to ensure the reliable and reliable link, the system needs to have the capability of flexibly switching the communication rate, that is, when the link is interfered, the bandwidth of the transmission signal is reduced, so that the receiving sensitivity is improved, and the capability of matching filtering the optical signal with variable bandwidth is required, so that the link can be ensured to have enough redundancy, but no adaptive filtering method for realizing the optical signal with variable bandwidth is seen at present.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a self-adaptive matched filtering system of a bandwidth-variable optical signal and a matching method thereof. The invention aims to solve the problem that the prior art is difficult to solve the self-adaptive matched filtering of the bandwidth-variable optical signal, creatively provides the self-adaptive matched filtering method of the bandwidth-variable optical signal, remarkably improves the communication usability of a space communication link under various interferences, and provides reliable guarantee for the communication of a space long distance and large capacity.
The technical scheme adopted for solving the technical problems is as follows:
a self-adaptive matched filtering system of a bandwidth-variable optical signal comprises a three-terminal interface unit and a filtering regulation and control unit; the bandwidth-variable optical signals sequentially pass through a three-terminal interface unit, the bandwidth value of the optical signals is obtained through measurement and calculation, and the signals of the three-terminal interface unit enter a 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 refrigerating sheet a, an optical filter b, a TEC refrigerating sheet b, an anti-reflection termination module and a temperature tuning control module, wherein an output port of the three-terminal interface unit (a 2 port of the optical circulator) 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 refrigerating sheet a is connected with the optical filter a, the TEC refrigerating sheet b is connected with the optical filter b, a port 1 of the temperature tuning control module is connected with the TEC refrigerating sheet a, a port 2 of the temperature tuning control module is connected with the TEC refrigerating sheet b, a port 3 of the temperature tuning control module is connected with a spectrum monitoring module b in the three-terminal 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 f 1 GHz～f 2 The random change between GHz is 1 to less than or equal to f 1 ≤100，1≤f 2 ≤100，f 1 ≤f 2 The method comprises the steps of carrying out a first treatment on the surface of the The bandwidth variation of the bandwidth-variable optical signal is a slow-varying 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 structure or a Fourier transform 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 of the optical signal enters a spectrum monitoring module a, and the other part of the optical signal enters an optical circulator port 1 and is output from a port 2 to enter a filtering regulation and control unit; in the filtering regulation and control unit, the whole signal containing noise is reflected and transmitted after the optical signal passes through the optical filter a, the reflected light returns to the optical circulator port 2, the transmitted light enters the optical filter b to be still reflected and transmitted, the reflected light returns according to the original path, the transmitted light is connected into the anti-reflection termination module to prevent echo reflection caused by uneven section of the optical fiber, and all the signals reflected back to the optical circulator port 2 are output through the 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 sheet a and the TEC refrigerating sheet b through the temperature tuning control module, the temperature can enable the center wavelength of the optical filter to shift left to enable the wavelength to be smaller or shift right to enable the wavelength to be larger, 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 self-adaptive matched filtering system of the bandwidth-variable optical signal, which comprises the following steps:
(1) As shown in fig. 1, the center wavelength of the bandwidth-variable optical signal is λ s With a bandwidth of Deltalambda s The bandwidth is changeable, after the optical isolator a and the optical splitter a are sequentially passed through, the optical splitter a is divided into two parts, a signal on the port 3 of the optical splitter a enters the spectrum monitoring module a, the 3dB bandwidth value of the optical signal is measured and calculated, and the signal on the port 2 of the optical splitter a enters the filtering regulation and control unit through the optical circulator to carry out bandwidth matched filtering;
(2) The filter bandwidths of the optical filter a and the optical filter b are respectively delta lambda a And Deltalambda b The central wavelength is lambda a And lambda (lambda) b The method comprises the steps of carrying out a first treatment on the surface of the The center wavelengths of the optical filters a and b shift left or right with temperature change, so that the two filters are combined to form a filterThe bandwidth of the wave can be correspondingly increased or decreased; fitting out the central wavelength and the temperature T of the optical filter a according to the test data of the central wavelength of the optical filter along with the temperature change 1 Curve function lambda of (2) a (T 1 ) Fitting the center wavelength and temperature T of the light-emitting filter b 2 Curve function lambda of (2) b (T 2 )；
(3) Measuring the center wavelength lambda of the current input optical signal according to the step (1) s And spectral bandwidth Deltalambda s Numerical values as input conditions, combined curve function lambda a (T 1 ) And curve function lambda b (T 2 ) To achieve a center wavelength and spectral bandwidth consistent with those of the input optical signal, the temperature T required by the optical filter a required at that time is calculated 1 And the temperature T required by the optical filter b 2 ；
(4) Temperature tuning control is respectively carried out on the TEC refrigerating sheet a and the TEC refrigerating sheet b, so that the temperature of the optical filter a reaches T 1 The temperature of the optical filter b reaches T 2 。
(5) The spectrum monitoring module b is used for 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, 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, the temperatures of the optical filter a and the optical filter b do not need to be adjusted; if the difference is inconsistent, calculating the difference value of the central wavelength measured by the spectrum monitoring module a (3-port signal of the optical splitter a) and the spectrum monitoring module b (3-port signal of the optical splitter b), and the difference value of the spectral bandwidths of the spectrum monitoring module a (3-port signal of the optical splitter a) and the spectrum monitoring module b (3-port signal of the optical splitter 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 wavelength 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 is delta lambda s When the temperature is changed, the temperature tuning control module calculates a new T 1 And T 2 The temperature T of the optical filter a and the temperature T of the optical filter b are respectively adjusted in real time 1 And T 2 So that the input optical signal is in dynamic change processThe middle filtering bandwidth is always consistent with the spectrum bandwidth of the input optical signal, 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 through methods such as grating reflection or Fourier transform, and other channel resources are not required 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 satisfied. Compared with the traditional single fixed bandwidth optical filter, the method adopts the cascade optical filter to realize combined reflection spectrum filtering, the size of the reflection spectrum filtering bandwidth can be flexibly adjusted by changing the temperature, the bandwidth of an input optical signal can be matched, in addition, the matching error caused by echo noise in an optical path can be further accurately adjusted through spectrum monitoring at an output end, and the method is not disclosed and reported at home and abroad at present.
(3) And can realize compatibility of various modulation modes. The method adopts a reflection type filtering method in the optical domain, does not need to know the modulation format of the optical signal, and only needs to measure the spectral bandwidth of the optical signal, so that the method 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 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 pattern effect diagram of an output optical signal in the case of the matched bandwidth filtering and the non-matched bandwidth filtering, fig. 3 (a) is an eye pattern effect diagram of an optical signal output with a filtering bandwidth smaller than the optical signal bandwidth, fig. 3 (b) is an eye pattern effect diagram of an optical signal output with a filtering bandwidth equal to the optical signal bandwidth, and fig. 3 (c) is an eye pattern effect diagram of an optical signal output with a filtering bandwidth larger than the optical signal bandwidth.
Detailed Description
The invention will be further described with reference to the drawings and examples.
The technical principle of the invention is as follows:
1. principle of space high-speed optical communication
The space high-speed optical communication process mainly comprises transmitting, transmitting and receiving. In the transmission process, first, high-speed optical communication is generated, and usually, a mach-zehnder modulator (MZM) is used to implement the MZM, where a transfer function is:
Figure GDA0004075321410000051
in the formula (1), E out (t) and E in (t) input and output light fields for modulator, respectively, V π The half-wave voltage to be modulated is determined by the material of the modulator. V (V) in (t) is the high-speed signal voltage applied to the modulator, V bias Is the bias voltage of the modulator.
When V is bias ＝V π 、V in (t)＝V π When (t) ·a (t), a (t) = ±1 (a (t) represents 1 code and 0 code in the pseudo random NRZ code differentially encoded in advance), a high-speed optical signal can be generated. The output optical signal expression, brought into equation (1), is as follows:
Figure GDA0004075321410000052
the modulated optical signal is amplified by a high-power optical amplifier and then transmitted by an optical antenna, and the expression of the optical signal received at a receiving end is as follows:
E RX (t)＝A(t)E out (t) (3)
in the formula (3), E RX (t) represents the optical field of the received optical signal and A (t) represents the channel time-varying attenuation coefficient.
The receiving end adopts an optical filter to filter broadband noise, the optical filter is a space phase grating formed in an optical fiber core, the optical fiber core mode of forward transmission and the optical fiber core mode of backward transmission are coupled through the grating, when one beam of light is transmitted through the Bragg grating, each small section of optical fiber with the refractive index changed can only reflect light waves with corresponding specific wavelength, namely Bragg wavelength, and light waves with other wavelengths are continuously transmitted, so that the grating forms the transmission and the transmission of incident waves, and the reflection wavelength is the Bragg wavelength:
λ B ＝2n eff Λ (4)
in the formula (4), n eff The fiber core equivalent refractive index is Λ, and the fiber grating period is Λ. The bandwidth of the grating can be calculated according to the following formula:
Figure GDA0004075321410000053
in formula (5), δn 0 For the difference in refractive index of the cladding and the core, η is the ratio of the energy in the core. The reflection at the peak wavelength is approximately as follows:
Figure GDA0004075321410000054
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-optical effect, stress variations on the fiber can affect the equivalent refractive index and grating period; due to the thermo-optic effect, the temperature drift change also changes the equivalent refractive index, and there is an influence of thermal expansion and thermal contraction, and the relationship between the reflection wavelength and the temperature, the elasto-optic coefficient, the thermal expansion coefficient and the thermo-optic coefficient is as follows:
λ'＝λ B (1-ρα)Δε+λ B (α+ξ)ΔΤ+λ B (7)
in the formula (7), lambda' is the changed reflection wavelength, and ρalpha, alpha, ζ, Δε and ΔT are respectively the elasto-optical coefficient, the thermal expansion coefficient, the thermo-optical coefficient, the stress variation and the temperature variation.
When the filter element is used in optical communication, the change of the center wavelength caused by the thermo-optical effect is considered without considering the elasto-optical effect, and as can be seen from the equation (7),wavelength shift is proportional to temperature, and center wavelength lambda of optical filter a and optical filter b are proportional to temperature a And lambda (lambda) b And optical filter surface temperature T 1 And T 2 The relationship of (2) can be expressed as follows:
λ a ＝a 1 T 1 2 +b 1 T 1 +c 1 (8)
λ b ＝a 2 T 2 2 +b 2 T 2 +c 2 (9)
wherein a1, b1 and c1 are defined by the wavelength lambda of the optical filter a a With temperature T 1 And (5) performing secondary fitting on the result data of the change test to obtain the product. a2, b2 and c2 are defined by the wavelength lambda of the optical filter b b With temperature T 2 And (5) performing secondary fitting on the result data of the change test to obtain the product.
The bandwidths of optical filter a and optical filter b are Δλ, respectively a And Deltalambda b (Δλ a ＜Δλ b ) As shown in fig. 2, the temperature T is adjusted according to the required filter bandwidth to be a fixed value 1 And T 2 Matched components form a matched filter bandwidth delta lambda. The minimum value of Deltalambda is Deltalambda 1 For the minimum bandwidth in both optical filters, i.e. with the optical filter a bandwidth Δλ a In agreement, as shown in fig. 2 (a); the maximum value of Deltalambda is Deltalambda 2 For the bandwidth delta lambda of the optical filter a a And optical filter b bandwidth delta lambda b As shown in fig. 2 (b); the bandwidth between the maximum and minimum is Deltalambda 3 The upper wavelength lambda of the filtered spectrum is combined by two optical filters U And a lower wavelength lambda L The spacing between them is shown in fig. 2 (c). Summarizing the above, the following formula is obtained:
Δλ 1 ＝Δλ a (10)
Δλ 2 ＝Δλ a +Δλ b (11)
Figure GDA0004075321410000061
by introducing the formula (8) and the formula (9) into the formula (12), a group can be obtainedThe combined filter bandwidth delta lambda 3 And temperature variable T 1 And T 2 The relationship of (2) is as follows:
Figure GDA0004075321410000071
as can be seen from equation (13), T is varied 1 And T 2 Can realize different filter bandwidths delta lambda 3 Thereby correlating with the spectral bandwidth Deltalambda of the input optical signal s And keeping consistent, and realizing optimal matched filtering. In addition, the center wavelength lambda of the input optical signal is required to be consistent when the spectral bandwidths are kept s Consistent with the center wavelength lambda' of the combined filtered spectrum, the following equation is satisfied:
Figure GDA0004075321410000072
by taking the formulas (8) and (9) into the formula (14), the combined filtered spectrum center wavelength and temperature variation T can be obtained 1 And T 2 The relationship of (2) is as follows:
Figure GDA0004075321410000073
spectral bandwidth delta lambda of input optical signal s And a center wavelength lambda s Are all known values which can be obtained by testing, so the temperature T at the moment is calculated by the known values 1 And T 2 . The addition and subtraction operations are performed on the combination formula (13) and formula (15), respectively, to obtain the following formula:
Δλ s -2λ s ＝-2(a 1 T 1 2 +b 1 T 1 +c 1 )+Δλ a (16)
Δλ s +2λ s ＝2(a 2 T 2 2 +b 2 T 2 +c 2 )+Δλ b (17)
t is obtained by solving the root of the quadratic function in the formulas (16) and (17) 1 And T 2 Is represented by the following formula:
Figure GDA0004075321410000074
Figure GDA0004075321410000075
from the above derivation, 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 lambdaa (T1) of the central wavelength of the optical filter a and the temperature T1 is fitted, and a curve function lambdab (T2) of the central wavelength of the optical filter b and the temperature T2 is fitted; (2) In obtaining the spectral bandwidth Deltalambda of the input optical signal s And a center wavelength lambda s After the values, the temperatures T1 and T2 can be calculated; (3) The surface temperature of the optical filter a and the optical filter b respectively reach T1 and T2 through a temperature control means, and the filtering spectral bandwidth and the central wavelength of the filtering spectrum formed at the moment are consistent with the input optical signal, so that the matched filtering effect is achieved. As shown in fig. 3 (b), when the matched filtering effect is achieved, the eye pattern of the output signal has excellent characteristics of large opening degree, clean interior of the eye pattern, small variance of 1 level and 0 level noise, and the like; if the filter 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 bandwidth of the filter band is greater than the bandwidth of the optical signal, 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 reduced, as shown in fig. 3 (c).
Examples:
based on the technical principle, the invention provides a bandwidth-variable adaptive matched filtering device for realizing optimal receiving of variable-rate signals, namely, firstly, the spectral bandwidth and the center wavelength of an input optical signal are measured and calculated by a spectrum monitoring method, and the temperature T required by an optical filter a and an optical filter b is further calculated according to the data result of the spectral bandwidth and the center wavelength of the input optical signal 1 And T 2 . The optical filter a and the optical filter b are controlled by temperatureThe surface temperature of the alloy reaches T respectively 1 And T 2 The bandwidth of the filtering spectrum formed at the moment is consistent with the central wavelength of the filtering spectrum and the input optical signal, so that the matched filtering effect is achieved.
The feasibility of the invention can be illustrated by the following examples:
a self-adaptive matched filtering system of a bandwidth-variable optical signal comprises a three-terminal interface unit and a filtering regulation and control unit; the bandwidth-variable optical signals sequentially pass through a three-terminal interface unit, the bandwidth value of the optical signals is obtained through measurement and calculation, and the signals of the three-terminal interface unit enter a 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 refrigerating sheet a, an optical filter b, a TEC refrigerating sheet b, an anti-reflection termination module and a temperature tuning control module, wherein an output port of the three-terminal interface unit (a 2 port of the optical circulator) 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 refrigerating sheet a is connected with the optical filter a, the TEC refrigerating sheet b is connected with the optical filter b, a port 1 of the temperature tuning control module is connected with the TEC refrigerating sheet a, a port 2 of the temperature tuning control module is connected with the TEC refrigerating sheet b, a port 3 of the temperature tuning control module is connected with a spectrum monitoring module b in the three-terminal 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 randomly changed between f1 (GHz) and 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 f1 is more than or equal to f2; the bandwidth variation of the bandwidth-variable optical signal is a slow-varying 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 structure or a Fourier transform 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 of the optical signal enters a spectrum monitoring module a, and the other part of the optical signal enters an optical circulator port 1 and is output from a port 2 to enter a filtering regulation and control unit; in the filtering regulation and control unit, the whole signal containing noise is reflected and transmitted after the optical signal passes through the optical filter a, the reflected light returns to the optical circulator port 2, the transmitted light enters the optical filter b to be still reflected and transmitted, the reflected light returns according to the original path, the transmitted light is connected into the anti-reflection termination module to prevent echo reflection caused by uneven section of the optical fiber, and all the signals reflected back to the optical circulator port 2 are output through the 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 sheet a and the TEC refrigerating sheet b through the temperature tuning control module, the temperature can enable the center wavelength of the optical filter to shift left to enable the wavelength to be smaller or shift right to enable the wavelength to be larger, 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 filtering device for a bandwidth-variable optical signal includes the following steps:
(1) After the optical signal is transmitted in a long space distance, the optical signal is input to the self-adaptive matched filtering device, and the optical field expression of the received optical signal can be expressed by the following formula:
E RX (t)＝A(t)E out (t)
(2) The broadband noise filtering is performed by using an optical filter at the receiving end, and the filtering is shown in fig. 1. The spectrum monitoring module a can measure the spectrum width and the center 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 the optical circulator;
(3) Wavelength shift is proportional to temperature, and center wavelength lambda of optical filter a and optical filter b a And lambda (lambda) b And optical filter surface temperature T 1 And T 2 The relationship of (a) can be obtained by a quadratic fit (a quadratic fit is more accurate than a first fit):
λ a ＝a 1 T 1 2 +b 1 T 1 +c 1
λ b ＝a 2 T 2 2 +b 2 T 2 +c 2
(4) In obtaining the spectral bandwidth Deltalambda of the input optical signal s And a center wavelength lambda s After the values, the temperatures T corresponding to the optical filter a and the optical filter b can be calculated 1 And T 2 Temperature T 1 And T 2 The computational expression is as follows:
Figure GDA0004075321410000101
Figure GDA0004075321410000102
(5) The temperature tuning control module takes temperature control measures for the TEC refrigerating sheet a and the TEC refrigerating sheet b, so that the surface temperatures of the optical filter a and the optical filter b respectively reach T 1 And T 2 And meanwhile, the spectrum monitoring module b monitors the spectrum bandwidth and the center wavelength of the optical signal after filtering at the moment and feeds back the deviation between the spectrum bandwidth of the input optical signal and the spectrum bandwidth of the output optical signal to the filtering regulation and control unit.
(6) The filtering regulation and control unit further corrects the temperature T 1 And T 2 So that the spectral bandwidth and the center wavelength after filtering are consistent with the input optical signal,achieving the effect of matched filtering.
Thus, the adaptive matched filtering process of the bandwidth-variable optical signal is realized through the steps.
The embodiment shows that the self-adaptive matched filtering method for the bandwidth-variable optical signal provided by the invention realizes bandwidth matched filtering output of the variable-rate optical signal, remarkably reduces noise in the signal, effectively improves the effective signal-to-noise ratio of the signal, provides reliable guarantee for large-capacity communication of a space long distance, and can be widely applied to a space laser communication receiving system.

Claims (8)

1. The self-adaptive matched filtering system for the bandwidth-variable optical signal comprises a three-terminal interface unit and a filtering regulation and control unit, and is characterized in that:
the self-adaptive matched filtering system of the received bandwidth-variable optical signal sequentially passes through a three-terminal interface unit, the bandwidth value of the optical signal is obtained through 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 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 refrigerating sheet a, an optical filter b, a TEC refrigerating sheet b, an anti-reflection termination module and a temperature tuning control module, wherein an output port of the three-terminal interface unit is connected with the optical filter a, a port 2 of the optical circulator is an output port of the three-terminal interface unit, 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 refrigerating sheet a is connected with the optical filter a, the TEC refrigerating sheet b is connected with the optical filter b, a port 1 of the temperature tuning control module is connected with the TEC refrigerating sheet a, a port 2 of the temperature tuning control module is connected with the TEC refrigerating sheet b, a port 3 of the temperature tuning control module is connected with a spectrum monitoring module b in the three-terminal interface unit, and a port 4 of the temperature tuning control module is connected with the spectrum monitoring module a.
2. The adaptive matched filtering system of a variable bandwidth optical signal of claim 1, wherein:
the 3dB bandwidth of the bandwidth-variable optical signal is f 1 GHz～f 2 The random change between GHz is 1 to less than or equal to f 1 ≤100，
1≤f 2 ≤100，f 1 ≤f 2 The method comprises the steps of carrying out a first treatment on the surface of the The bandwidth variation of the bandwidth-variable optical signal is a slow-varying characteristic.
3. The adaptive matched filtering system of a variable bandwidth optical signal of 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 modulated optical signal QPSK, 16QAM, 64 QAM.
4. The adaptive matched filtering system of a variable bandwidth optical signal of claim 1, wherein:
the spectrum monitoring module is of a grating type structure or a Fourier transform type structure.
5. The adaptive matched filtering system of a variable bandwidth optical signal of 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 adaptive matched filtering system of a variable bandwidth optical signal of claim 1, wherein:
the optical filter is a fiber grating filter or a multilayer dielectric film filter.
7. The adaptive matched filtering system of a variable bandwidth optical signal of 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 of the optical signal enters a spectrum monitoring module a, and the other part of the optical signal enters an optical circulator port 1 and is output from a port 2 to enter a filtering regulation and control unit; in the filtering regulation and control unit, the whole signal containing noise is reflected and transmitted after the optical signal passes through the optical filter a, the reflected light returns to the optical circulator port 2, the transmitted light enters the optical filter b to be still reflected and transmitted, the reflected light returns according to the original path, the transmitted light is connected into the anti-reflection termination module to prevent echo reflection caused by uneven section of the optical fiber, and all the signals reflected back to the optical circulator port 2 are output through the 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 sheet a and the TEC refrigerating sheet b through the temperature tuning control module, the temperature can enable the center wavelength of the optical filter to shift left to enable the wavelength to be smaller or shift right to enable the wavelength to be larger, dynamic adjustment control of the filtering bandwidth is achieved, and the filtering bandwidth is matched with the optical signal bandwidth.
8. A method of matching using the adaptive matched filtering system of the variable bandwidth optical signal of claim 1, comprising the steps of:
(1) The center wavelength of the bandwidth-variable optical signal is lambda s The bandwidth is delta lambda s The bandwidth is changeable, after the optical isolator a and the optical splitter a are sequentially passed through, the optical splitter a is divided into two parts, a signal on the port 3 of the optical splitter a enters the spectrum monitoring module a, the 3dB bandwidth value of the optical signal is measured and calculated, and the signal on the port 2 of the optical splitter a enters the filtering regulation and control unit through the optical circulator to carry out bandwidth matched filtering;
(2) The filter bandwidths of the optical filter a and the optical filter b are respectively delta lambda a And Deltalambda b The central wavelength is lambda a And lambda (lambda) b The method comprises the steps of carrying out a first treatment on the surface of the The center wavelengths of the optical filters a and b shift left or right with temperature change, and thusThe filter bandwidth formed by combining the two filters can be correspondingly increased or reduced; fitting out the central wavelength and the temperature T of the optical filter a according to the test data of the central wavelength of the optical filter along with the temperature change 1 Curve function lambda of (2) a (T 1 ) Fitting the center wavelength and temperature T of the light-emitting filter b 2 Curve function lambda of (2) b (T 2 )；
(3) Measuring the center wavelength lambda of the current input optical signal according to the step (1) s And spectral bandwidth Deltalambda s Numerical values as input conditions, combined curve function lambda a (T 1 ) And curve function lambda b (T 2 ) To achieve a center wavelength and spectral bandwidth consistent with those of the input optical signal, the temperature T required by the optical filter a required at that time is calculated 1 And the temperature T required by the optical filter b 2 ；
(4) Temperature tuning control is respectively carried out on the TEC refrigerating sheet a and the TEC refrigerating sheet b, so that the temperature of the optical filter a reaches T 1 The temperature of the optical filter b reaches T 2 ；
(5) The spectrum monitoring module b is used for 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, 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, the temperatures of the optical filter a and the optical filter b do not need to be adjusted; if the difference is inconsistent, calculating the difference of the central wavelengths measured by the spectrum monitoring module a and the spectrum monitoring module b and the difference 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 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 is delta lambda s When the temperature is changed, the temperature tuning control module calculates a new T 1 And T 2 The temperature T of the optical filter a and the temperature T of the optical filter b are respectively adjusted in real time 1 And T 2 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 the matched filtering is realized。
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