CN108011664B - Noise separation method for optical fiber sensing remote demodulation system - Google Patents

Noise separation method for optical fiber sensing remote demodulation system Download PDF

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CN108011664B
CN108011664B CN201710941939.1A CN201710941939A CN108011664B CN 108011664 B CN108011664 B CN 108011664B CN 201710941939 A CN201710941939 A CN 201710941939A CN 108011664 B CN108011664 B CN 108011664B
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noise
optical power
transmission module
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remote transmission
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汪樟海
张红
徐汉锋
王巍
李东明
葛辉良
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715th Research Institute of CSIC
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07955—Monitoring or measuring power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07953—Monitoring or measuring OSNR, BER or Q
    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2537—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to scattering processes, e.g. Raman or Brillouin scattering
    • 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
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/67—Optical arrangements in the receiver
    • H04B10/671—Optical arrangements in the receiver for controlling the input optical signal
    • H04B10/672—Optical arrangements in the receiver for controlling the input optical signal for controlling the power of the input optical signal
    • H04B10/674—Optical arrangements in the receiver for controlling the input optical signal for controlling the power of the input optical signal using a variable optical attenuator
    • 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
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/69—Electrical arrangements in the receiver
    • H04B10/697—Arrangements for reducing noise and distortion

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  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

The invention discloses a noise separation method for an optical fiber sensing remote demodulation system. Selecting a group of input optical power sequences of the remote transmission module within the maximum transmittable optical power range of the remote transmission module; demodulating and calculating the current system phase noise power spectrum density of each remote transmission module input optical power value in the sequence to obtain a noise power spectrum density mean value in a target frequency range; according to the functional relation between the power spectral densities of different types of noise and the input optical power value of the remote transmission module, the contributions of different types of noise components are obtained through a least square fitting method, and the separation of different types of noise sources is achieved. The method realizes the separation of two system noise sources of ASE noise and DRS noise of the optical fiber sensing remote demodulation system, provides a method for accurately positioning the main noise source which has the largest contribution to the system noise, and indicates the direction for the development of the system noise optimization work.

Description

Noise separation method for optical fiber sensing remote demodulation system
Technical Field
The invention relates to the field of optical fiber sensing, in particular to a noise separation method for an optical fiber sensing remote demodulation system.
Background
The optical fiber sensing remote demodulation system needs to demodulate the detection signals returned by the optical fiber sensing array within dozens or even hundreds of meters. The transmission loss of the long-distance optical fiber makes the optical signal returned by the optical fiber sensing array extremely weak, so that the signal-to-noise ratio of the photoelectric detection result cannot meet the noise index requirement of the system, and an optical amplifier is generally required to be added into an optical fiber transmission link to make up for the transmission loss of the long-distance optical fiber. Common optical amplifiers are erbium-doped fiber amplifiers (EDFAs), distributed fiber raman amplifiers, and the like. When an optical amplification scheme is adopted, the optical power of an array return signal meets the signal-to-noise ratio requirement required by photoelectric detection, but the signal-to-noise ratio of the photoelectric detection signal is also deteriorated in the optical amplification process, and the main mechanism is as follows: one is Amplified Spontaneous Emission (ASE) noise caused by ASE light of an optical amplifier and random beat frequency of signal light; the second is that the optical amplifier amplifies the signal light and also amplifies the Double Rayleigh Scattering (DRS) light in the transmission fiber, and the beat frequency of the two will cause DRS noise. The two noise sources have different mechanisms and are mutually independent random processes, and the contribution to the total noise of the system is different under different system parameters. In the actual system noise optimization process, the main noise source which contributes more to the two noise sources is optimized, so that the total noise level of the system can be effectively reduced, and therefore, the main noise source of the system needs to be accurately positioned. However, in the actual noise testing process, only the total noise of the system can be obtained, and the magnitude of each noise component cannot be independently tested, so that the system noise needs to be separated, and the total noise of the system is optimized by analyzing the main noise source of the system and adopting a targeted noise optimization scheme.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a noise separation method of an optical fiber sensing remote demodulation system aiming at the noise optimization requirement in the current optical fiber sensing remote demodulation application process.
The object of the present invention is achieved by the following technical means. The noise separation method of the optical fiber sensing remote demodulation system comprises the following steps:
(1) selecting an optical power sequence P composed of a group of different optical power values within the maximum transmittable optical power range of the remote transmission modules[k]As an input optical power sequence for the teletransmission module;
(2) for sequence Ps[k]The input optical power value of each remote transmission module in the system is demodulated and calculated to obtain the noise power spectral density mean value D in the target frequency rangephase[k]；
(3) According to the functional relation Dphase＝k1/Ps+k2For noise power spectral density sequences D in (1) and (2)phase[k]And an optical power sequence Ps[k]Fitting by using a least square method to obtain a constant coefficient k1And k2Respectively corresponding to ASE noise and DRS noise components, and calculating the input optical power sequence P at the moments[k]Noise power spectral density sequence D due to corresponding ASE noise and DRS noisephase_ASE[k]And Dphase_DRS[k]And separation of two noise sources is realized.
Preferably, the input optical power of the remote transmission module is set by the demodulator through a first MEMS optical attenuator and monitored through the 1/99 coupler; the demodulator adjusts the average value of the input optical power of the detector to be constant through a second MEMS optical attenuator.
The invention principle is as follows: the amplified spontaneous radiation noise and the double Rayleigh scattering noise are used as two main noise sources of the optical fiber sensing remote demodulation system, the noise mechanisms are different, and the power superposition of the amplified spontaneous radiation noise and the double Rayleigh scattering noise becomes the main source of the system noise. Relative intensity noise power spectral density D caused by amplified spontaneous emission noise and double Rayleigh scattering noiseASEAnd DDRSRespectively as follows:
Figure BDA0001430854240000021
Figure BDA0001430854240000022
in the formula, ρASEIs ASE optical power spectral density, PsIs the signal light power; rεdirIs the normalized autocorrelation function, F, of the directly transmitted light.]Representing a fourier transform. Total relative intensity noise power spectral density D of systemRINIs the superposition of two kinds of noise:
DRIN(f)＝DASE(f)+DDRS(f) (3)
visible amplified spontaneous emission noise power spectral density is inversely proportional to signal light power, and double rayleigh scattering noise power spectral densityThe degree is only related to the normalized autocorrelation function of the light source and is not related to the signal light power. Relative intensity noise power spectral density D by signal demodulation processRINWill be converted into phase noise D of the systemphaseThe two are generally proportional. Thus the total phase noise power spectral density D of the systemphaseIs a function of the signal light power and can be expressed as:
Figure BDA0001430854240000023
in the formula, k1And k2Are constant coefficients related to system parameters and respectively represent amplified spontaneous emission noise and double Rayleigh scattering noise terms. Therefore, if an optical power sequence P consisting of a set of different optical power values is measureds[k]Corresponding system total phase noise power spectrum density sequence Dphase[k]Namely, the coefficient k can be obtained by a least square fitting method1And k2So as to respectively calculate the contributions D of amplified spontaneous emission noise and double Rayleigh scattering noise to the total phase noise of the system when different signal light powers are calculatedphase_ASEAnd Dphase_DRS. According to the size of the calculation result, the main noise source of the system at the moment can be determined, and experimental basis is provided for further system noise optimization work.
The invention has the beneficial effects that: the method realizes the separation of two system noise sources of ASE noise and DRS noise of the optical fiber sensing remote demodulation system, provides a method for accurately positioning the main noise source which has the largest contribution to the system noise, and indicates the direction for the development of the system noise optimization work. The method is simple to implement, the testing precision can be improved by increasing the length of the fitting sequence, and the separation result is high in precision and good in reliability.
Drawings
FIG. 1 is a functional block diagram of a typical test system configuration.
Fig. 2 shows the results of system noise test and noise separation for a remote demodulation system using the method of the present invention.
In the figure: 1. the optical transmitter comprises an optical transmitting module, 2, a first MEMS optical attenuator, 3, 1/99 couplers, 4, a remote transmission module, 5, a sensing array, 6, a second MEMS optical attenuator, 7, a detector, 8, an optical power meter, 9 and a demodulator.
Detailed Description
The invention will be described in detail below with reference to the following drawings:
FIG. 1 is a functional block diagram of a typical test system configuration. The optical transmission module 1 generates a downlink optical signal required by the remote transmission module 4, the optical signal transmitted by the optical transmission module passes through the first MEMS optical attenuator 2 and the 1/99 coupler 3 before entering the remote transmission module 4, 1% of the output end of the coupler is connected with the optical power meter 8, and 99 times of the number of the optical power meter 8 is used as the input optical power P of the remote transmission modulesThe return signal of the remote transmission module 4 after passing through the sensing array 5 passes through a second MEMS optical attenuator 6 and is converted into an electrical signal by a detector 7, and the electrical signal enters a demodulator 9, and the demodulator 9 demodulates the electrical signal to obtain the phase noise power spectral density of the system. The demodulator 9 controls the light attenuation proportion by controlling the input electric signals of the two MEMS optical attenuators 2 and 6. The two MEMS optical attenuators 2 and 6 work cooperatively to ensure that the input optical power of the detector remains substantially unchanged when the remote transmission module has different input optical powers, so that the noise performance of the detector is not deteriorated, and therefore, in the actual adjustment process, when the attenuation of the first MEMS optical attenuator 2 is increased by X dB, the attenuation of the second MEMS optical attenuator 6 is always decreased by X dB correspondingly.
The method comprises the following implementation steps:
(1) adjusting the optical transmission module 1 and the first MEMS optical attenuator 2 to make the remote transmission module work in the maximum input optical power state which can be transmitted by the system, adjusting the second MEMS optical attenuator 6 to make the detector 7 work in the optimal input optical power, and recording the input optical power P of the remote transmission module at the moments[1]Demodulating to obtain the power spectrum density of the system phase noise at the moment, and obtaining the mean value D of the power spectrum density of the phase noise in the target frequency rangephase[1](ii) a (2) Gradually reducing the input optical power of the remote transmission module to generate an input optical power sequence P of the remote transmission modules[k](ii) a (3) Adjusting the two MEMS attenuators 2, 6 according to the generated sequence Ps[k]Testing corresponding system phase noise one by onePower spectral density sequence Dphase[k](ii) a (4) According to the functional relation Dphase＝k1/Ps+k2To sequence Dphase[k]And Ps[k]Fitting by using a least square method to obtain a constant coefficient k1And k2Respectively corresponding to ASE noise and DRS noise components, and calculating the input optical power sequence P at the moments[k]Noise power spectral density sequence D due to corresponding ASE noise and DRS noisephase_ASE[k]And Dphase_DRS[k]Thereby realizing the separation of two noise sources.
FIG. 2 is a set of data and a curve fitted thereto. The abscissa is the sequence of the input optical power P for the remote transmissions[k]Unit dBm; the ordinate is the corresponding noise power spectral density sequence Dphase[k]In dB/Hz. The circle points are the test results and the black curves are the fitting results.
Table 1 shows the test data corresponding to fig. 2 and the fitting and noise separation results thereof. The first column is the teletransmission input optical power sequence Ps[k](ii) a The second column is the measured noise power spectral density sequence Dphase[k](ii) a Third column is Dphase[k]The fitting result of (2) is basically consistent with the actual test result; the fourth and fifth columns are ASE noise and DRS noise power spectral density sequences D calculated from the noise fit resultsphase_ASE[k]And Dphase_DRS[k]I.e. the noise separation result. It can be seen that when the input optical power for remote transmission is-29.6 dBm, the power spectral densities of the system phase noise caused by the ASE noise and the DRS noise are-91.0 dB/Hz and-91.1 dB/Hz, which are basically equivalent to each other, and the effective optimization of the system noise can be realized only when the influence of the ASE noise and the DRS noise is reduced. And if the remote transmission input optical power is-39.6 dBm, the influence (-81.0dB/Hz) of the ASE noise is far greater than that of the DRS noise (-91.1dB/Hz), namely the ASE noise is the main noise source of the system, and the effective optimization of the system noise can be realized only by reducing the influence of the ASE noise.
TABLE 1
Figure BDA0001430854240000031
Figure BDA0001430854240000041
It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.

Claims (1)

1. A noise separation method for an optical fiber sensing remote demodulation system is characterized by comprising the following steps:
(1) selecting an optical power sequence P composed of a group of different optical power values within the maximum transmittable optical power range of the remote transmission modules[k]As an input optical power sequence for the teletransmission module;
(2) for sequence Ps[k]The input optical power value of each remote transmission module in the system is demodulated and calculated to obtain the noise power spectral density mean value D in the target frequency rangephase[k]；
(3) According to the functional relation Dphase＝k1/Ps+k2For noise power spectral density sequences D in (1) and (2)phase[k]And an optical power sequence Ps[k]Fitting by using a least square method to obtain a constant coefficient k1And k2Respectively corresponding to ASE noise and DRS noise components, and calculating the input optical power sequence P at the moments[k]Noise power spectral density sequence D due to corresponding ASE noise and DRS noisephase_ASE[k]And Dphase_DRS[k]The separation of two noise sources is realized;
a return signal of the remote transmission module (4) passing through the sensing array (5) passes through a second MEMS optical attenuator (6), is converted into an electric signal through a detector (7), and enters a demodulator (9), and the demodulator (9) demodulates the electric signal to obtain the phase noise power spectral density of the system; the demodulator (9) controls the light attenuation proportion by controlling the input electric signals of the first MEMS optical attenuator (2) and the second MEMS optical attenuator (6); the two MEMS optical attenuators work cooperatively to ensure that the input optical power of the detector is kept basically unchanged when the remote transmission module has different input optical powers; the input optical power of the remote transmission module (4) is set by a demodulator (9) through a first MEMS optical attenuator (2) and monitored through an 1/99 coupler (3); the input optical power mean value of the detector (7) is adjusted to be constant by the demodulator (9) through the second MEMS optical attenuator (6).
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101008570A (en) * 2007-01-29 2007-08-01 浙江大学 Method for separating thermal noise, shot noise and intensity noise of optical fiber gyroscope
CN102629731A (en) * 2012-02-14 2012-08-08 浙江嘉莱光子技术有限公司 Control method for simultaneously stabilizing laser wavelength and power and control device thereof
CN104316217A (en) * 2014-10-23 2015-01-28 国网河南省电力公司周口供电公司 On-line monitoring system based on brillouin scattering self-temperature-measurement optical fiber composite guide wire
CN104931080A (en) * 2015-06-09 2015-09-23 北京航空航天大学 Noise separation method based on optical transmission-reception system of fiber sensor
CN105739215A (en) * 2016-02-02 2016-07-06 上海交通大学 High-precision bi-directional optical fiber time transmission light amplification method and device
CN106767905A (en) * 2016-11-29 2017-05-31 浙江大学 Separate double detector type optical fibre gyro light source and electronic noise correlation calculations method
EP3192191A1 (en) * 2014-09-12 2017-07-19 BAE Systems PLC Signal processing apparatus

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101008570A (en) * 2007-01-29 2007-08-01 浙江大学 Method for separating thermal noise, shot noise and intensity noise of optical fiber gyroscope
CN102629731A (en) * 2012-02-14 2012-08-08 浙江嘉莱光子技术有限公司 Control method for simultaneously stabilizing laser wavelength and power and control device thereof
EP3192191A1 (en) * 2014-09-12 2017-07-19 BAE Systems PLC Signal processing apparatus
CN104316217A (en) * 2014-10-23 2015-01-28 国网河南省电力公司周口供电公司 On-line monitoring system based on brillouin scattering self-temperature-measurement optical fiber composite guide wire
CN104931080A (en) * 2015-06-09 2015-09-23 北京航空航天大学 Noise separation method based on optical transmission-reception system of fiber sensor
CN105739215A (en) * 2016-02-02 2016-07-06 上海交通大学 High-precision bi-directional optical fiber time transmission light amplification method and device
CN106767905A (en) * 2016-11-29 2017-05-31 浙江大学 Separate double detector type optical fibre gyro light source and electronic noise correlation calculations method

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