WO2022042759A1 - 基于光纤参量放大的分布式脉冲光放大器和放大及性能表征方法 - Google Patents

基于光纤参量放大的分布式脉冲光放大器和放大及性能表征方法 Download PDF

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WO2022042759A1
WO2022042759A1 PCT/CN2021/120470 CN2021120470W WO2022042759A1 WO 2022042759 A1 WO2022042759 A1 WO 2022042759A1 CN 2021120470 W CN2021120470 W CN 2021120470W WO 2022042759 A1 WO2022042759 A1 WO 2022042759A1
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signal
pulse
light
optical
pulse light
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French (fr)
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李政颖
傅雪蕾
熊犇
郑洲
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武汉理工大学
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    • H—ELECTRICITY
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    • H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
    • H01S3/10015—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by monitoring or controlling, e.g. attenuating, the input signal
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    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/39—Non-linear optics for parametric generation or amplification of light, infrared or ultraviolet waves
    • G02F1/395—Non-linear optics for parametric generation or amplification of light, infrared or ultraviolet waves in optical waveguides
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    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
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    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
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    • G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
    • G01D5/35354—Sensor working in reflection
    • G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
    • G01D5/35361—Sensor working in reflection using backscattering to detect the measured quantity using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/3537—Optical fibre sensor using a particular arrangement of the optical fibre itself
    • G01D5/35377—Means for amplifying or modifying the measured quantity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
    • G01M11/3109—Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094076—Pulsed or modulated pumping
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1307—Stabilisation of the phase
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2383—Parallel arrangements
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
    • H01S3/302—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects in an optical fibre
    • H—ELECTRICITY
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0085—Modulating the output, i.e. the laser beam is modulated outside the laser cavity
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    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1305—Feedback control systems

Definitions

  • the invention relates to the technical field of optical sensing, in particular to a distributed pulse optical amplifier based on optical fiber parametric amplification and an amplification and performance characterization method.
  • Optical fiber has the characteristics of on-site passive, anti-electromagnetic interference, corrosion resistance, strong adaptability to harsh environments, low signal transmission loss, high transmission process safety, and can integrate tens of thousands of sensing units in one optical fiber, so it is especially suitable for Long-term uninterrupted monitoring of super-large, long-line structures or equipment, such as high-speed railways, oil and gas pipelines, urban pipeline networks, etc.; and key fields with high requirements for information security and harsh environments, such as national defense, aerospace, power industry, etc. .
  • optical time-domain reflectometry In distributed optical fiber sensing, it is not only necessary to measure environmental physical quantities such as temperature, strain, and vibration, but also to locate signals. Among them, optical time-domain reflectometry (OTDR) is currently the most widely used. ) technology: take pulse light as input, and use the time inversion of the back-transmitted sensing signal to return to the input to calculate the position of the sensing point to realize the positioning of the sensing signal. Since the sensing signal is generated by the input pulse light, when the fiber loss and environmental noise cause the pulse power attenuation and extinction ratio after long-distance transmission, the signal-to-noise ratio of the sensing signal will be degraded, resulting in a decrease in the sensing accuracy. .
  • the signal-to-noise ratio of the sensing signal can be improved by enhancing the scattering efficiency.
  • enhanced scattering will inevitably lead to an increase in fiber transmission loss, limiting the fiber transmission distance.
  • Using the fiber grating array to enhance the signal reflectivity can also improve the signal-to-noise ratio of the sensing signal. But such methods also cause signal crosstalk and limit transmission distance.
  • Improving the extinction ratio of the input pulse is another method to improve the signal-to-noise ratio, which is mainly realized by using an optical modulator or a multi-level optical modulator with a higher extinction ratio.
  • the main drawback of this method is that the system is complex and energy consumption is high, and it cannot fundamentally solve the problems of power attenuation and extinction ratio drop caused by optical fiber transmission.
  • the third method is to carry out distributed amplification, and realize the amplification of the sensing pulse by using the amplification produced by the nonlinear scattering effect of the fiber, including stimulated Brillouin scattering and stimulated Raman scattering.
  • This kind of method has a remarkable signal amplification effect, but it not only amplifies the pulse itself, but also amplifies the area where there should be no light in the non-pulse duration interval, but actually has weak light leakage, resulting in a decrease in the pulse extinction ratio, which eventually leads to the sensing signal signal. Noise ratio drops. It can be seen that none of the existing methods can achieve the effect of simultaneously amplifying the pulse power and the extinction ratio in a distributed manner.
  • the purpose of the present invention is to provide a distributed pulsed optical amplifier based on optical fiber parametric amplification and an amplification and performance characterization method.
  • the present invention utilizes high-power pulsed light as pump light to generate optical fiber parametric amplification effect near the zero-dispersion wavelength of the optical fiber, Realize the power amplification of another sensing pulse light.
  • the low-power light leakage beyond the duration of the pump pulse light cannot achieve effective optical fiber parametric amplification, the light leakage of the sensing pulse light will not be amplified, so the effect of amplifying the pulse extinction ratio can be achieved at the same time.
  • the distributed pulsed optical amplifier based on optical fiber parametric amplification designed by the present invention includes a pump pulse light source, a sensing pulse light source, a synchronization device, a two-in-one optical coupler, an optical circulator, and a parametric amplifier fiber.
  • a first optical filter a photodetector and a signal acquisition device, wherein the outputs of the pump pulse light source and the sensing pulse light source are combined through a two-in-one optical coupler and then enter the first communication end of the optical circulator, and the optical ring After the second communication end of the shaper is outputted, it enters the parametric amplification fiber; the synchronization device is used to ensure that the pump pulse light output by the pump pulse light source and the sensing pulse light output by the sensing pulse light source are synchronized in pulse time.
  • the Rayleigh scattering effect in the parametric amplification fiber causes the pump pulse light and the sensing pulse light to generate scattered light opposite to the pulse transmission direction, and the scattered light opposite to the pulse transmission direction passes through the halo.
  • the second communication terminal of the optical circulator is input and output by the third communication terminal of the optical circulator. After passing through the first optical filter, only the scattered light signal of the sensing pulse is retained, and the photodetector is used for photoelectric conversion of the scattered light signal of the sensing pulse.
  • the signal acquisition device is used to collect the photoelectric signal of the sensing pulse scattering according to the pulse synchronization trigger signal, and obtain the signal power and signal-to-noise ratio that change with the length of the parametric amplified fiber according to the scattered photoelectric signal of the sensing pulse.
  • the pump pulse light source By adjusting the pump pulse light source The pump pulse power and wavelength and the sensing pulse power and wavelength of the sensing pulse light source, so that the signal power and signal-to-noise ratio that change with the length of the parametric amplifier fiber reach the corresponding preset values of signal power and signal-to-noise ratio.
  • the distributed pulse amplifier based on optical fiber parametric amplification proposed by the present invention only amplifies the pulse part of the sensing pulse light, and does not amplify the low optical power part outside the pulse duration period, so it can simultaneously amplify the power and extinction of the sensing pulse Therefore, when applied to a distributed sensing system based on OTDR to realize sensing signal positioning, it can effectively alleviate the loss of sensing pulse optical power and the decrease in extinction ratio caused by long-distance optical fiber transmission, so as to improve long-distance distributed optical fiber sensing.
  • the pump pulse light and the signal pulse light used in the present invention are in the same wavelength band, so the distance between the pump pulse light and the sensing pulse light caused by chromatic dispersion in long-distance optical fiber transmission will be significantly smaller than that of the distributed light.
  • Raman amplification in distributed first-order Raman amplification, there is a wavelength difference of about 100 nm between the pump pulse light and the sensing pulse light;
  • the present invention When the present invention is applied to the 1550nm band, it can ensure that both the pump pulse light and the signal pulse light have low transmission loss, which is obviously better than the case of distributed Raman amplification (when the sensing pulse light is set in the 1550nm band, The central wavelength of the Raman pump light is about 1450 nm, and the transmission loss of the silica fiber is significantly higher than that in the 1550 nm band).
  • Fig. 1 is the structural representation of the present invention
  • FIG. 2 is a schematic structural diagram of a pump pulse light source in the present invention
  • FIG. 3 is a schematic structural diagram of the sensing pulse light source in the present invention.
  • 1 pump pulse light source
  • 1.1 first laser
  • 1.2 first optical intensity modulator
  • first electrical pulse source 1.4
  • first electrical amplifier 1.5
  • optical amplifier 1.6
  • second optical filter 1.7
  • Polyization Controller 2
  • Sensing Pulse Light Source 2.1—Second Laser
  • 2.2 Second Optical Intensity Modulator
  • 2.3 Second Electrical Pulse Source
  • 2.4 Second Electrical Amplifier
  • 3 Synchromse Generator
  • 4 two-in-one optical coupler
  • 5 optical circulator
  • 6 parametric amplifier fiber
  • 7 first optical filter
  • 8 photoelectric detector
  • 9 signal acquisition equipment.
  • the distributed pulsed optical amplifier based on optical fiber parametric amplification designed by the present invention includes a pump pulse light source 1, a sensing pulse light source 2, a synchronization device 3, a two-in-one optical coupler 4, an optical ring 5, a parametric amplifier fiber 6, a first optical filter 7, a photodetector 8 and a signal acquisition device 9, wherein the outputs of the pump pulse light source 1 and the sensing pulse light source 2 are combined via a two-in-one optical coupler 4 After entering the first communication end (a port) of the optical circulator 5, it is output by the second communication end (b port) of the optical circulator 5 and then enters the parametric amplification fiber 6; the synchronization device 3 is used to ensure the output of the pump pulse light source 1
  • the pump pulse light and the sensing pulse light output by the sensing pulse light source 2 are synchronized in pulse time (the pulse time is centered and aligned (that is, the repetition frequency of the pump and the sensing pulse is the same, and there is always overlap
  • the photodetector 8 is used to detect the sensing pulse.
  • the scattered light signal is photoelectrically converted, and the signal acquisition device 9 is used to collect the scattered photoelectric signal of the sensing pulse according to the pulse synchronization trigger signal (according to the time corresponding to the pulse, determine the time period for signal acquisition, and synchronously trigger the acquisition), and according to the transmission time.
  • the signal power and signal-to-noise ratio that change with the length of the parametric amplification fiber 6 are obtained from the photoelectric signal of the sensing pulse scattering.
  • the The signal power and the signal-to-noise ratio that change with the length of the parametric amplification optical fiber 6 reach the corresponding preset values of the signal power and the signal-to-noise ratio.
  • the signal acquisition device 9 is used to calculate the signal power that changes with the length of the parametric amplification fiber 6 according to the time domain change of the sensing pulse scattering photoelectric signal, combined with the speed of light in the parametric amplification fiber 6, and then combined with the system ( That is, the amplifier of the present invention) noise floor, and calculate the signal-to-noise ratio that varies with the length of the parametric amplifying optical fiber 6 .
  • the pump pulse light source 1 includes a first laser 1.1, a first optical intensity modulator 1.2, a first electrical pulse source 1.3, a first electrical amplifier 1.4, an optical amplifier 1.5, and a first electrical pulse source 1.3.
  • the amplifier 1.4 is connected to the electrical signal input end of the first optical intensity modulator 1.2.
  • the first optical intensity modulator 1.2 uses the electrical pulse signal to perform optical intensity modulation on the laser signal, and converts the continuous wave laser signal into a pulsed optical signal.
  • the pulse width is determined by The electrical pulse signal applied to the first optical intensity modulator 1.2 determines that the pulsed optical signal passes through the optical amplifier 1.5, the second optical filter 1.6 and the polarization controller 1.7 in sequence to form a pump pulse optical signal.
  • the first electrical pulse source 1.3 is used to receive the synchronization control signal sent by the synchronization device 3 .
  • the sensing pulse light source 2 includes a second laser 2.1, a second light intensity modulator 2.2, a second electrical pulse source 2.3 and a second electrical amplifier 2.4.
  • the laser signal output terminal is connected to the optical signal input terminal of the second optical intensity modulator 2.2
  • the electrical pulse signal output terminal of the second electrical pulse source 2.3 is connected to the electrical signal input terminal of the second optical intensity modulator 2.2 through the second electrical amplifier 2.4
  • the second light intensity modulator 2.2 uses an electrical pulse signal to perform light intensity modulation on the laser signal to form a sensing pulse light signal.
  • the second electrical pulse source 2.3 is used to receive the synchronization control signal sent by the synchronization device 3 .
  • the pump pulse light transmits energy to the sensing pulse light through the optical fiber parametric amplification process, so as to realize distributed optical amplification of the sensing pulse light.
  • the zero dispersion wavelength of the optical fiber should be close to and slightly smaller than the central wavelength of the pump pulse light (usually 1-5 nm smaller than the pump wavelength).
  • the transmission loss of the parametric amplification fiber should be as small as possible, which is preferably not higher than the transmission loss of the existing communication fiber.
  • the Rayleigh scattering effect in the parametric amplification fiber 6 causes the pump pulse light and the sensing pulse light to generate back-transmitted scattered light, wherein the back-scattered light signal of the sensing pulse is distributed light Amplified distributed optical fiber sensing signal;
  • the first optical filter 7 is used to obtain the distributed optical fiber sensing signal amplified by distributed light, and its center wavelength is ⁇ S , and the passband range should ensure that the sensing pulse light scattering signal is retained, and the pump pulse light is completely filtered out. scattered signal;
  • the power and relative phase difference of the pump pulse light, the sensing pulse light and the idler pulse light with the fiber length z are given by The following set of coupled wave equations are given by:
  • P P , P S and P I are the powers of the pump pulse light, the sensing pulse light and the idler pulse light, respectively
  • ⁇ is the nonlinear coefficient of the fiber
  • ⁇ is the relative phase difference
  • z is the length of the parametric amplification fiber, and is given by is given by:
  • ⁇ 3 and ⁇ 4 are the third and fourth derivative values of the propagation constant ⁇ ( ⁇ ) at the zero-dispersion circular frequency ⁇ 0 , respectively. Since the effects of higher-order dispersion can be ignored, only the effects of ⁇ 3 and ⁇ 4 on the linear phase mismatch are considered here.
  • ⁇ P (z), ⁇ S (z) and ⁇ I (z) are the phases of the pump pulse light, the sensing pulse light and the idler pulse light, respectively. are given together, ⁇ (z) represents the relative phase difference (the relative phase relationship between the pump light, the sensing light and the idler light) with the light transmission distance in the parametric amplifier fiber; ⁇ P and ⁇ S , respectively represents the circular frequency of the pump and sense pulses.
  • the second term is the phase adaptation term caused by the nonlinear phase shift in the transmission process.
  • the fiber parametric amplifier works in the pumped non-depleted mode (P P >> P S ), then formula (6) can be simplified as
  • P S (z) represents the change of the optical power of the sensing pulse with the length of the fiber
  • P S (0) represents the optical power of the input sensing pulse
  • P I (z) represents the change of the optical power of the idler pulse with the length of the fiber
  • sinh is a hyperbolic sine function
  • the parametric gain coefficient g is given by
  • ⁇ is the linear attenuation coefficient of the fiber.
  • the power of the sensing pulse light can be calculated according to formula (10) and the input optical power P S (0) of the sensing pulse light.
  • the power of the sensing pulse light needs to be solved by solving equations (1)-(4 )calculate.
  • a pulsed light amplification method based on the above amplifier which comprises the following steps:
  • Step 1 the pump pulse light source 1 emits a pump pulse light with a center wavelength of ⁇ P ;
  • Step 2 The sensing pulse light source 2 emits sensing pulse light with a center wavelength of ⁇ S , the pulse width of the pump pulse light is larger than that of the sensing pulse light, the polarization of the pump pulse light and the sensing pulse light are consistent, and the center wavelength ⁇ S Tuning in the amplifier gain spectrum range, that is, tuning in the range from ⁇ S,start to ⁇ S,stop , first set the wavelength to be ⁇ S,start ;
  • Step 3 The two-in-one optical coupler 4 combines the amplified pump pulse light and the sensing pulse light, and the synchronization device 3 ensures that the pump pulse light and the sensing pulse light are synchronized in pulse time;
  • Step 4 The time-synchronized pump pulse light and sensing pulse light are input from the first communication end of the optical circulator 5, and the second communication end of the optical circulator 5 enters the parametric amplification fiber 6 after being output.
  • a kind of amplifier performance characterization method utilizing the above-mentioned pulsed light amplification method it is characterized in that, it comprises the following steps:
  • Step 101 The Rayleigh scattering effect in the parametric amplification fiber 6 causes the pump pulse light and the sensing pulse light to generate scattered light opposite to the pulse transmission direction, and the scattered light opposite to the pulse transmission direction passes through the second communication of the optical circulator 5 After the terminal is input, it is output from the third communication terminal of the optical circulator 5, and the scattered light opposite to the pulse transmission direction enters the first optical filter 7 to filter out the scattered signals from the pump pulse light and the idler pulse light, and obtain the The scattered light signal of the sensing pulse light is converted into an electrical signal by the photodetector 8 and collected by the signal acquisition device 9;
  • Step 102 Turn off the pump pulse light source 1, and according to the time-domain electrical signal (the electrical signal that changes with time) collected by the signal acquisition device 9, invert and calculate to obtain the wavelength of ⁇ S, and the sensing pulse light scattering signal power and signal at start time.
  • the variation of the noise ratio with the length of the parametric amplification optical fiber 6 is denoted as P off, RS ( ⁇ S, start , z) and SNR off, RS ( ⁇ S, start , z), where z represents the length of the parametric amplification optical fiber 6;
  • Step 103 Take the wavelength ⁇ S, step as the interval (the setting of the wavelength interval is related to the actual fineness of the gain spectrum measurement, and can usually be set at 0.1 nm), gradually tune the center wavelength of the sensing pulse light, and repeat step 102 until Its wavelength is ⁇ S,stop , and the variation of the scattering signal power of the sensing pulse light and the signal-to-noise ratio with the length of the parametric amplifying fiber 6 and the center wavelength of the sensing pulse light when the pump pulse light source 1 is turned off is obtained, denoted as P off,RS ( ⁇ S ,z) and SNR off,RS ( ⁇ S ,z);
  • Step 104 Turn on the pump pulse light source 1, and according to the time-domain electrical signal collected by the signal acquisition device 9, inversion and calculation obtain a wavelength of ⁇ S, start , the sensing pulse light scattering under the condition of the center wavelength and power of the current pump pulse light source
  • the variation of signal power and signal-to-noise ratio with the length of the parametric amplifier fiber 6 is recorded as P on,RS ( ⁇ S,start ,z) and SNR on,RS ( ⁇ S,start ,z) respectively;
  • Step 105 With the wavelength ⁇ S,step as an interval, gradually tune the center wavelength of the sensing pulse light, repeat step 104 until its wavelength is ⁇ S,stop , and obtain the sensing pulse light under the current pump pulse light source center wavelength and power conditions
  • the variation of scattered signal power and signal-to-noise ratio with the length of the parametric amplifier fiber 6 and the center wavelength of the sensing pulse light is denoted as P on,RS ( ⁇ S ,z) and SNR on,RS ( ⁇ S ,z);
  • Step 107 Adjust the central wavelength and power settings of the pump pulse light according to the requirements for the gain spectrum and noise index spectrum, and repeat steps 104 to 106 until the gain spectrum and noise spectrum meet the design requirements.

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Abstract

本发明公开了一种基于光纤参量放大的分布式脉冲光放大器，它包括泵浦脉冲光源、传感脉冲光源、同步设备、二合一光耦合器、光环形器、参量放大光纤、第一光滤波器、光电检测器和信号采集设备。本发明利用高功率脉冲光作为泵浦光，在光纤零色散波长附近产生光纤参量放大效应，实现对另一传感脉冲光的功率放大。同时，由于泵浦脉冲光存续时间段以外的低功率漏光无法实现有效的光纤参量放大，因此传感脉冲光的漏光不会被放大，因而能同时达到放大脉冲消光比的效果。

Description

基于光纤参量放大的分布式脉冲光放大器和放大及性能表征方法 技术领域
本发明涉及光传感技术领域，具体地指一种基于光纤参量放大的分布式脉冲光放大器和放大及性能表征方法。
背景技术
光纤具有现场无源、抗电磁干扰、耐腐蚀、恶劣环境适应性强、信号传输损耗低、传输过程安全性高、可以在一根光纤中集成数万个传感单元等特性，因此特别适用于对超大型、长线型结构或装备的长期不间断监测，如高速铁路、油气管道、城市管网等；以及对信息安全要求高、环境恶劣的关键领域，如国防军事、航空航天、电力工业等。
在分布式光纤传感中，不仅要实现对温度、应变、振动等环境物理量的测量，还要能进行信号定位，而其中目前应用最广泛的是光时域反射(Optical time-domain reflectometry，OTDR)技术：以脉冲光作为输入，利用背向传输的传感信号返回输入端的时间反演计算传感点位置而实现传感信号定位。由于传感信号依赖于输入的脉冲光产生，因此当光纤损耗和环境噪声使得长距离传输后的脉冲功率衰减、消光比下降时，就会引起传感信号信噪比劣化，导致传感精度下降。从光纤本身出发，可以通过增强散射效率来提高传感信号的信噪比。然而，增强散射必然导致光纤传输损耗上升，限制光纤传输距离。采用光纤光栅阵列增强信号反射率同样可以提高传感信号信噪比。但是这类方法还会造成信号串扰，也会限制传输距离。提高输入脉冲消光比是另一种提升信噪比的方法，主要靠采用具有更高消光比的光调制器或多级光调制器实现。这一方法的主要缺陷在于系统复杂、能耗高，也并不能从根本上解决光纤传输引起的功率衰减和消光比下降问题。第三种方法是进行分布式放大，利用包括受激布里渊散射和受激拉曼散射在内的光纤非线性散射效应产生的放大作用实现传感脉冲的放大。这类方法信号放大效果显著，但是不仅对脉冲本身有放大效果，也会放大非脉冲存续区间本应无光、 但实际上有微弱漏光的区域，造成脉冲消光比下降，最终导致传感信号信噪比下降。可以看到，现有方法均不能达到同时对脉冲功率和消光比进行分布式放大的效果。
发明内容
本发明的目的就是要提供一种基于光纤参量放大的分布式脉冲光放大器和放大及性能表征方法，本发明利用高功率脉冲光作为泵浦光，在光纤零色散波长附近产生光纤参量放大效应，实现对另一传感脉冲光的功率放大。同时，由于泵浦脉冲光存续时间段以外的低功率漏光无法实现有效的光纤参量放大，因此传感脉冲光的漏光不会被放大，因而能同时达到放大脉冲消光比的效果。
为实现此目的，本发明所设计的基于光纤参量放大的分布式脉冲光放大器，它包括泵浦脉冲光源、传感脉冲光源、同步设备、二合一光耦合器、光环形器、参量放大光纤、第一光滤波器、光电检测器和信号采集设备，其中，泵浦脉冲光源和传感脉冲光源的输出经由二合一光耦合器合路后进入光环形器的第一通信端，由光环形器的第二通信端输出后进入参量放大光纤；同步设备用于保证泵浦脉冲光源输出的泵浦脉冲光和传感脉冲光源输出的传感脉冲光在脉冲时间上同步，信号采集设备用于对同步设备进行脉冲同步触发信号采集，参量放大光纤中的瑞利散射效应使泵浦脉冲光和传感脉冲光产生与脉冲传输方向相反的散射光，与脉冲传输方向相反的散射光经光环形器的第二通信端输入后由光环形器的第三通信端输出，经第一光滤波器后仅保留传感脉冲散射光信号，光电检测器用于对传感脉冲散射光信号进行光电转换，信号采集设备用于根据脉冲同步触发信号对传感脉冲散射光电信号进行采集，并根据传感脉冲散射光电信号获得随参量放大光纤长度变化的信号功率以及信噪比，通过调节泵浦脉冲光源的泵浦脉冲功率和波长以及传感脉冲光源的传感脉冲功率和波长，使随参量放大光纤长度变化的信号功率和信噪比达到均达到对应的信号功率和信噪比预设值。
本发明的有益效果：
1、本发明提出的基于光纤参量放大的分布式脉冲放大器仅放大传感脉冲光的脉冲部分，而不放大脉冲存续时间段以外的低光功率部分，因此可以同时放大传感脉冲的功率和消光比，因而在应用于基于OTDR实现传感信号定位的分布式传感系统时能有效缓解长距离光纤传输引起的传感脉冲光功率损耗和消光比下降，从而达到提升长距离分布式光纤传感中远端传感信号信噪比的目的；
2、本发明采用的泵浦脉冲光与信号脉冲光在同一个波段，因而在长距离光纤传输中由于色度色散引起的泵浦脉冲光与传感脉冲光的走离程度会明显小于分布式拉曼放大的情况(在分布式一阶拉曼放大中，泵浦脉冲光与传感脉冲光存在约100nm的波长差)；
3、本发明应用于1550nm波段时，可保证泵浦脉冲光和信号脉冲光均具有低的传输损耗，，明显优于分布式拉曼放大的情况(当传感脉冲光设置在1550nm波段时，拉曼泵浦光中心波长约为1450nm，石英光纤的传输损耗明显高于1550nm波段)。
附图说明
图1为本发明的结构示意图；
图2为本发明中泵浦脉冲光源的结构示意图；
图3为本发明中传感脉冲光源的结构示意图。
其中，1—泵浦脉冲光源、1.1—第一激光器、1.2—第一光强度调制器、1.3—第一电脉冲源、1.4—第一电放大器、1.5—光放大器、1.6—第二光滤波器、1.7—偏振控制器、2—传感脉冲光源、2.1—第二激光器、2.2—第二光强度调制器、2.3—第二电脉冲源、2.4—第二电放大器、3—同步设备、4—二合一光耦合器、5—光环形器、6—参量放大光纤、7—第一光滤波器、8—光电检测器、9—信号采集设备。
具体实施方式
以下结合附图和具体实施例对本发明作进一步的详细说明：
本发明所设计的基于光纤参量放大的分布式脉冲光放大器，如图1所示，它包括泵浦脉冲光源1、传感脉冲光源2、同步设备3、二合一光耦合器4、光环形器5、参量放大光纤6、第一光滤波器7、光电检测器8和信号采集设备9，其中，泵浦脉冲光源1和传感脉冲光源2的输出经由二合一光耦合器4合路后进入光环形器5的第一通信端(a端口)，由光环形器5的第二通信端(b端口)输出后进入参量放大光纤6；同步设备3用于保证泵浦脉冲光源1输出的泵浦脉冲光和传感脉冲光源2输出的传感脉冲光在脉冲时间上同步(脉冲时间上居中对齐(就是泵浦和传感两个脉冲重复频率一致，时间上始终有重叠)，因为考虑到光纤传输有色散，所以设计的泵浦脉冲比传感脉冲长，以保证长距离传输之后两个时间上不偏离)，信号采集设备9用于对同步设备3进行脉冲同步触发信号采集，参量放大光纤6中的瑞利散射效应使泵浦脉冲光和传感脉冲光产生与脉冲传输方向相反的散射光，与脉冲传输方向相反的散射光经光环形器5的第二通信端输入后由光环形器5的第三通信端(c端口)输出，经第一光滤波器7(带通光滤波器)后仅保留传感脉冲散射光信号，光电检测器8用于对传感脉冲散射光信号进行光电转换，信号采集设备9用于根据脉冲同步触发信号对传感脉冲散射光电信号进行采集(根据脉冲对应的时间，确定信号采集的时间段，同步触发进行采集)，并根据传感脉冲散射光电信号获得随参量放大光纤6长度变化的信号功率以及信噪比，通过调节泵浦脉冲光源1的泵浦脉冲功率和波长以及传感脉冲光源2的传感脉冲功率和波长，使随参量放大光纤6长度变化的信号功率和信噪比达到均达到对应的信号功率和信噪比预设值。
上述技术方案中，所述信号采集设备9用于根据传感脉冲散射光电信号的时域变化，结合参量放大光纤6中的光速，计算随参量放大光纤6长度变化的信号功率，再结合系统(即本发明的放大器)本底噪声，计算随参量放大光纤6长度变化的信噪比。
上述技术方案中，如图2所示，所述泵浦脉冲光源1包括第一激光器1.1、第一光强度调制器1.2、第一电脉冲源1.3、第一电放大器1.4、光放大器1.5、第二光滤波器1.6和偏振控制器1.7，第一激光器1.1的激光信号输出端连接第一光强度调制器1.2的光信号输入端，第一电脉冲源1.3的电脉冲信号输出端通过第一电放大器1.4连接第一光强度调制器1.2的电信号输入端，第一光强度调制器1.2利用电脉冲信号对激光信号进行光强度调制，将连续波的激光信号变成脉冲光信号，脉冲宽度由施加在第一光强度调制器1.2上的电脉冲信号决定，脉冲光信号依次经过光放大器1.5、第二光滤波器1.6和偏振控制器1.7后形成泵浦脉冲光信号。
上述技术方案中，所述第一电脉冲源1.3用于接收同步设备3发出的同步控制信号。
上述技术方案中，如图3所示，所述传感脉冲光源2包括第二激光器2.1、第二光强度调制器2.2、第二电脉冲源2.3和第二电放大器2.4，第二激光器2.1的激光信号输出端连接第二光强度调制器2.2的光信号输入端，第二电脉冲源2.3的电脉冲信号输出端通过第二电放大器2.4连接第二光强度调制器2.2的电信号输入端，所述第二光强度调制器2.2利用电脉冲信号对激光信号进行光强度调制形成传感脉冲光信号。
上述技术方案中，所述第二电脉冲源2.3用于接收同步设备3发出的同步控制信号。
本发明在所述的参量放大光纤6中，泵浦脉冲光通过光纤参量放大过程将能量传递给传感脉冲光，实现对传感脉冲光的分布式光放大。为保证光纤参量放大的有效性，此光纤的零色散波长应该接近且略小于(一般是比泵浦波长小1～5nm)泵浦脉冲光的中心波长。为了达到大的有效放大距离，参量放大光纤的传输损耗应尽量小，以不高于现有通信用光纤的传输损耗为宜。
在参量放大过程发生的同时，参量放大光纤6中的瑞利散射效 应使泵浦脉冲光和传感脉冲光产生背向传输的散射光，其中传感脉冲背向散射光信号为经分布式光放大的分布式光纤传感信号；
第一光滤波器7用于获取经分布式光放大的分布式光纤传感信号，其中心波长为λ S，通带范围应保证保留传感脉冲光散射信号，并完全滤除泵浦脉冲光散射信号；
利用光纤参量放大实现传感信号分布式光放大的原理、以及对分布式光放大性能表征的具体过程如下：
当上述系统中的泵浦脉冲光和传感脉冲光同时进入高非线性光纤，且二者时间上同步时，发生光纤参量放大，泵浦脉冲光的能量传递给传感脉冲光，对其产生放大，同时产生波长为λ I的闲频脉冲光，中心波长为λ I＝2λ P-λ S。在传感脉冲光功率较低，因此高阶四波混频产物可忽略的前提下，泵浦脉冲光、传感脉冲光和闲频脉冲光的功率及相对相位差随光纤长度z的变化由下面一组耦合波方程给出：
Figure PCTCN2021120470-appb-000001
Figure PCTCN2021120470-appb-000002
Figure PCTCN2021120470-appb-000003
Figure PCTCN2021120470-appb-000004
其中P P、P S和P I分别为泵浦脉冲光、传感脉冲光和闲频脉冲光的功率，γ为光纤的非线性系数，θ为相对相位差，z表示参量放大光纤长度，由下式给出：
θ(z)＝Δβz+2φ P(z)-φ S(z)-φ I(z)   (5)
其中Δβ为色散引起的线性相位失配，由下式给出
Figure PCTCN2021120470-appb-000005
式中β 3和β 4分别为传播常数β(ω)在零色散圆频率ω 0处的三阶导 数和四阶导数值。由于更高阶色散的影响可以忽略，这里只考虑β 3和β 4对线性相位失配的影响。φ P(z)、φ S(z)和φ I(z)分别为泵浦脉冲光、传感脉冲光和闲频脉冲光的相位，由其分别的初始相位以及传输过程产生的非线性相移共同给出，θ(z)表示相对相位差(泵浦光、传感光和闲频光之间的相对相位关系)随光在参量放大光纤中的传输距离的变化；ω P和ω S分别表示泵浦和传感脉冲光的圆频率。
当放大器工作在相位匹配条件下，即θ(z)≈π/2时，公式(4)中等号右边第三项可以忽略不计，此时有
Figure PCTCN2021120470-appb-000006
其中，第二项为由传输过程非线性相移引起的相位适配项。在较短的光纤中，光纤参量放大工作于泵浦未耗尽模式(P P＞＞P S)，则公式(6)可以简化为
Figure PCTCN2021120470-appb-000007
其中κ为相位失配参数，此时传感脉冲光和闲频脉冲光功率随光纤长度的变化由公式(9)、(10)给出
Figure PCTCN2021120470-appb-000008
Figure PCTCN2021120470-appb-000009
其中，P S(z)表示传感脉冲光功率随光纤长度的变化，P S(0)表示输入传感脉冲光功率，P I(z)表示闲频脉冲光功率随光纤长度的变化，sinh为双曲正弦函数，参量增益系数g由下式给出
Figure PCTCN2021120470-appb-000010
L为参量放大的有效作用光纤长度。考虑光纤无传输损耗时，L＝z。当光纤存在传输损耗时，
Figure PCTCN2021120470-appb-000011
其中α为光纤的线性衰减系数。
在泵浦脉冲光非耗尽假设成立时，传感脉冲光的功率可以根据公式(10)和传感脉冲光的输入光功率P S(0)计算。当泵浦脉冲光由于传输损耗，以及功率向传感脉冲光、闲频脉冲光的转移而使得非耗尽假设不成立时，则传感脉冲光的功率需要通过求解方程组(1)-(4)计算。这些计算方法可以为后述步骤中的泵浦光中心波长、功率调节提供依据。
一种基于上述放大器的脉冲光放大方法，它包括如下步骤：
步骤1：泵浦脉冲光源1发出中心波长为λ P的泵浦脉冲光；
步骤2：传感脉冲光源2发出中心波长为λ S的传感脉冲光，泵浦脉冲光的脉冲宽度大于传感脉冲光，泵浦脉冲光与传感脉冲光偏振保持一致，中心波长λ S在放大器增益谱范围内调谐，即从λ S,start到λ S,stop范围内调谐，首先设定波长为λ S,start；
步骤3：二合一光耦合器4将放大后的泵浦脉冲光与传感脉冲光合路，由同步设备3保证泵浦脉冲光与传感脉冲光在脉冲时间上同步；
步骤4：时间上同步的泵浦脉冲光与传感脉冲光由光环形器5的第一通信端输入，光环形器5的第二通信端输出后进入参量放大光纤6，在光纤传输过程中发生分布式光纤参量过程，泵浦脉冲光被消耗而传感脉冲光被放大，同时产生中心波长为1/λ I＝2/λ P-1/λ S的闲频脉冲光，实现传感脉冲光放大。
一种利用上述脉冲光放大方法的放大器性能表征方法，其特征在于，它包括如下步骤：
步骤101：参量放大光纤6中的瑞利散射效应使泵浦脉冲光和传感脉冲光产生与脉冲传输方向相反的散射光，与脉冲传输方向相反的散射光经光环形器5的第二通信端输入后由光环形器5的第三通信端输出，与脉冲传输方向相反的散射光进入第一光滤波器7滤除源自泵浦脉冲光和闲频脉冲光的散射信号，获得源自传感脉冲光的散射光信号，并由光电检测器8转换为电信号，并由信号采集设备9 采集；
步骤102：关闭泵浦脉冲光源1，根据信号采集设备9采集的时域电信号(随时间变化的电信号)，反演计算获得波长为λ S,start时传感脉冲光散射信号功率及信噪比随参量放大光纤6长度的变化，分别记为P off,RS(λ S,start,z)和SNR off,RS(λ S,start,z)，其中，z表示参量放大光纤6长度；
步骤103：以波长λ S,step为间隔(波长间隔的设置与实际对增益谱测量的精细度需求有关，通常可以设置在0.1nm)，逐步调谐传感脉冲光中心波长，重复步骤102，直至其波长为λ S,stop，获得泵浦脉冲光源1关闭时传感脉冲光散射信号功率及信噪比随参量放大光纤6长度和传感脉冲光中心波长的变化，记为P off,RS(λ S,z)和SNR off,RS(λ S,z)；
步骤104：打开泵浦脉冲光源1，根据信号采集设备9采集的时域电信号，反演计算获得波长为λ S,start时，当前泵浦脉冲光源中心波长和功率条件下传感脉冲光散射信号功率及信噪比随参量放大光纤6长度的变化，分别记为P on,RS(λ S,start,z)和SNR on,RS(λ S,start,z)；
步骤105：以波长λ S,step为间隔，逐步调谐传感脉冲光中心波长，重复步骤104，直至其波长为λ S,stop，获得当前泵浦脉冲光源中心波长和功率条件下传感脉冲光散射信号功率及信噪比随参量放大光纤6长度和传感脉冲光中心波长的变化，记为P on,RS(λ S,z)和SNR on,RS(λ S,z)；
步骤106：计算增益谱和噪声指数谱随参量放大光纤6长度的变化，即空间分辨的增益谱和噪声指数谱：G(λ S,z)＝P on,RS(λ S,z)-P off,RS(λ S,z)，NF(λ S,z)＝SNR on,RS(λ S,z)-SNR off,RS(λ S,z)；
步骤107：根据对增益谱和噪声指数谱的要求调整泵浦脉冲光中心波长和功率设置，重复步骤104至步骤106，直至增益谱和噪声谱符合设计要求。
本说明书未作详细描述的内容属于本领域专业技术人员公知的现有技术。

Claims (8)

  1. 一种基于光纤参量放大的分布式脉冲光放大器，其特征在于：它包括泵浦脉冲光源(1)、传感脉冲光源(2)、同步设备(3)、二合一光耦合器(4)、光环形器(5)、参量放大光纤(6)、第一光滤波器(7)、光电检测器(8)和信号采集设备(9)，其中，泵浦脉冲光源(1)和传感脉冲光源(2)的输出经由二合一光耦合器(4)合路后进入光环形器(5)的第一通信端，由光环形器(5)的第二通信端输出后进入参量放大光纤(6)；同步设备(3)用于保证泵浦脉冲光源(1)输出的泵浦脉冲光和传感脉冲光源(2)输出的传感脉冲光在脉冲时间上同步，信号采集设备(9)用于对同步设备(3)进行脉冲同步触发信号采集，参量放大光纤(6)中的瑞利散射效应使泵浦脉冲光和传感脉冲光产生与脉冲传输方向相反的散射光，与脉冲传输方向相反的散射光经光环形器(5)的第二通信端输入后由光环形器(5)的第三通信端输出，经第一光滤波器(7)后仅保留传感脉冲散射光信号，光电检测器(8)用于对传感脉冲散射光信号进行光电转换，信号采集设备(9)用于根据脉冲同步触发信号对传感脉冲散射光电信号进行采集，并根据传感脉冲散射光电信号获得随参量放大光纤(6)长度变化的信号功率以及信噪比，通过调节泵浦脉冲光源(1)的泵浦脉冲功率和波长以及传感脉冲光源(2)的传感脉冲功率和波长，使随参量放大光纤(6)长度变化的信号功率和信噪比达到均达到对应的信号功率和信噪比预设值。
  2. 根据权利要求1所述的基于光纤参量放大的分布式脉冲光放大器，其特征在于：所述信号采集设备(9)用于根据传感脉冲散射光电信号的时域变化，结合参量放大光纤(6)中的光速，计算随参量放大光纤(6)长度变化的信号功率，再结合系统本底噪声，计算随参量放大光纤(6)长度变化的信噪比。
  3. 根据权利要求1所述的基于光纤参量放大的分布式脉冲光放大器，其特征在于：所述泵浦脉冲光源(1)包括第一激光器(1.1)、 第一光强度调制器(1.2)、第一电脉冲源(1.3)、第一电放大器(1.4)、光放大器(1.5)、第二光滤波器(1.6)和偏振控制器(1.7)，第一激光器(1.1)的激光信号输出端连接第一光强度调制器(1.2)的光信号输入端，第一电脉冲源(1.3)的电脉冲信号输出端通过第一电放大器(1.4)连接第一光强度调制器(1.2)的电信号输入端，第一光强度调制器(1.2)利用电脉冲信号对激光信号进行光强度调制，将连续波的激光信号变成脉冲光信号，脉冲宽度由施加在第一光强度调制器(1.2)上的电脉冲信号决定，脉冲光信号依次经过光放大器(1.5)、第二光滤波器(1.6)和偏振控制器(1.7)后形成泵浦脉冲光信号。
  4. 根据权利要求3所述的基于光纤参量放大的分布式脉冲光放大器，其特征在于：所述第一电脉冲源(1.3)用于接收同步设备(3)发出的同步控制信号。
  5. 根据权利要求1或3所述的基于光纤参量放大的分布式脉冲光放大器，其特征在于：所述传感脉冲光源(2)包括第二激光器(2.1)、第二光强度调制器(2.2)、第二电脉冲源(2.3)和第二电放大器(2.4)，第二激光器(2.1)的激光信号输出端连接第二光强度调制器(2.2)的光信号输入端，第二电脉冲源(2.3)的电脉冲信号输出端通过第二电放大器(2.4)连接第二光强度调制器(2.2)的电信号输入端，所述第二光强度调制器(2.2)利用电脉冲信号对激光信号进行光强度调制形成传感脉冲光信号。
  6. 根据权利要求5所述的基于光纤参量放大的分布式脉冲光放大器，其特征在于：所述第二电脉冲源(2.3)用于接收同步设备(3)发出的同步控制信号。
  7. 一种基于权利要求1所述放大器的脉冲光放大方法，其特征在于，它包括如下步骤：
    步骤1：泵浦脉冲光源(1)发出中心波长为λ P的泵浦脉冲光；
    步骤2：传感脉冲光源(2)发出中心波长为λ S的传感脉冲光， 泵浦脉冲光的脉冲宽度大于传感脉冲光，泵浦脉冲光与传感脉冲光偏振保持一致，中心波长λ S在放大器增益谱范围内调谐，即从λ S,start到λ S,stop范围内调谐；
    步骤3：二合一光耦合器(4)将放大后的泵浦脉冲光与传感脉冲光合路，由同步设备(3)保证泵浦脉冲光与传感脉冲光在脉冲时间上同步；
    步骤4：时间上同步的泵浦脉冲光与传感脉冲光由光环形器(5)的第一通信端输入，光环形器(5)的第二通信端输出后进入参量放大光纤(6)，在光纤传输过程中发生分布式光纤参量过程，泵浦脉冲光被消耗而传感脉冲光被放大，同时产生中心波长为1/λ I＝2/λ P-1/λ S的闲频脉冲光，实现传感脉冲光放大。
  8. 一种利用权利要求7所述脉冲光放大方法的放大器性能表征方法，其特征在于，它包括如下步骤：
    步骤101：参量放大光纤(6)中的瑞利散射效应使泵浦脉冲光和传感脉冲光产生与脉冲传输方向相反的散射光，与脉冲传输方向相反的散射光经光环形器(5)的第二通信端输入后由光环形器(5)的第三通信端输出，与脉冲传输方向相反的散射光进入第一光滤波器(7)滤除源自泵浦脉冲光和闲频脉冲光的散射信号，获得源自传感脉冲光的散射光信号，并由光电检测器(8)转换为电信号，并由信号采集设备(9)采集；
    步骤102：关闭泵浦脉冲光源(1)，根据信号采集设备(9)采集的时域电信号，反演计算获得波长为λ S,start时传感脉冲光散射信号功率及信噪比随参量放大光纤(6)长度的变化，分别记为P off,RS(λ S,start,z)和SNR off,RS(λ S,start,z)，其中z表示参量放大光纤(6)长度；
    步骤103：以波长λ S,step为间隔，逐步调谐传感脉冲光中心波长，重复步骤102，直至其波长为λ S,stop，获得泵浦脉冲光源(1)关闭时传感脉冲光散射信号功率及信噪比随参量放大光纤(6)长度和传感 脉冲光中心波长的变化，记为P off,RS(λ S,z)和SNR off,RS(λ S,z)；
    步骤104：打开泵浦脉冲光源(1)，根据信号采集设备(9)采集的时域电信号，反演计算获得波长为λ S,start时，当前泵浦脉冲光源中心波长和功率条件下传感脉冲光散射信号功率及信噪比随参量放大光纤(6)长度的变化，分别记为P on,RS(λ S,start,z)和SNR on,RS(λ S,start,z)；
    步骤105：以波长λ S,step为间隔，逐步调谐传感脉冲光中心波长，重复步骤104，直至其波长为λ S,stop，获得当前泵浦脉冲光源中心波长和功率条件下传感脉冲光散射信号功率及信噪比随参量放大光纤(6)长度和传感脉冲光中心波长的变化，记为P on,RS(λ S,z)和SNR on,RS(λ S,z)；
    步骤106：计算增益谱和噪声指数谱随参量放大光纤(6)长度的变化，即空间分辨的增益谱和噪声指数谱：G(λ S,z)＝P on,RS(λ S,z)-P off,RS(λ S,z)，NF(λ S,z)＝SNR on,RS(λ S,z)-SNR off,RS(λ S,z)；
    步骤107：根据对增益谱和噪声指数谱的要求调整泵浦脉冲光中心波长和功率设置，重复步骤104至步骤106，直至增益谱和噪声谱符合设计要求。
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CN111964700A (zh) * 2020-08-28 2020-11-20 武汉理工大学 基于光纤参量放大的分布式脉冲光放大器和放大及性能表征方法

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CN114884570A (zh) * 2022-06-16 2022-08-09 北京泛在云科技有限公司 一种光纤窃听检测方法及装置
CN114884570B (zh) * 2022-06-16 2024-01-19 北京泛在云科技有限公司 一种光纤窃听检测方法及装置

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