WO2022006701A1 - 一种用于海洋温度及压力同步监测的多波长激光器 - Google Patents

一种用于海洋温度及压力同步监测的多波长激光器 Download PDF

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WO2022006701A1
WO2022006701A1 PCT/CN2020/100403 CN2020100403W WO2022006701A1 WO 2022006701 A1 WO2022006701 A1 WO 2022006701A1 CN 2020100403 W CN2020100403 W CN 2020100403W WO 2022006701 A1 WO2022006701 A1 WO 2022006701A1
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Prior art keywords
laser
phase
spectrum
wavelength
light
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PCT/CN2020/100403
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English (en)
French (fr)
Inventor
王昌
尚盈
倪家升
王晨
郭茜
宋志强
刘小会
赵文安
张发祥
王英英
黄胜
李常
曹冰
吕蕾
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山东省科学院激光研究所
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Priority to GB2301592.8A priority Critical patent/GB2612507A/en
Priority to DE112020007387.4T priority patent/DE112020007387T5/de
Priority to US18/019,451 priority patent/US20230288272A1/en
Priority to PCT/CN2020/100403 priority patent/WO2022006701A1/zh
Publication of WO2022006701A1 publication Critical patent/WO2022006701A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
    • G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
    • G01L1/246—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre using integrated gratings, e.g. Bragg gratings
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
    • 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
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
    • G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
    • G01L11/025—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means using a pressure-sensitive optical fibre
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • 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

Definitions

  • the present application relates to the technical field of marine environment monitoring, in particular to a multi-wavelength laser used for synchronous monitoring of ocean temperature and pressure.
  • seawater temperature and pressure Due to the vast and ever-changing ocean area, it is an important factor affecting the global climate, water, drought, typhoon and other natural disasters. Therefore, the marine environment is of great significance to weather forecasting and disaster warning. Among them, the measurement of seawater temperature and pressure is of great significance to the study of oceanography and marine environmental monitoring. For example, in the fields of marine scientific research and military affairs, it is necessary to obtain the dynamic changes of sea temperature profile and pressure in time.
  • the distributed optical fiber sensing technology can realize the continuous sensing and measurement of the measured physical quantities distributed along the length of the optical fiber, it can integrate the functions of sensing and transmission, and not only can complete the distributed environmental parameters along the entire length of the optical fiber.
  • Continuous measurement of time multi-dimensional distribution state information, and distributed measurement information can also be transmitted to the information processing center in real time and without loss.
  • the internal signal acquisition cost is low and the cost performance is high. Therefore, this technology is applied to a continuous space monitoring of ocean temperature and pressure.
  • the multi-wavelength laser source is the key device, and the price of the existing multi-wavelength laser source remains high, which seriously affects the large-scale promotion of distributed optical fiber sensing.
  • the multi-wavelength laser source has become an urgent problem to be solved by those skilled in the art.
  • embodiments of the present application provide a multi-wavelength laser for synchronous monitoring of ocean temperature and pressure.
  • the multi-wavelength laser for synchronous monitoring of ocean temperature and pressure provided in the embodiment of the present application, in a first implementation manner, includes:
  • the broad-spectrum laser source is used to output broad-spectrum laser light
  • the pulse controller is used for converting the broad-spectrum laser light output by the broad-spectrum laser source into broad-spectrum pulsed light;
  • the phase-shift grating unit is used for demodulating a plurality of pulsed lights of different wavelengths arranged in time series from the broad-spectrum pulsed light.
  • the laser further includes a first wavelength division multiplexer, wherein:
  • the first port of the first wavelength division multiplexer is connected to the output end of the pulse controller, the second port is connected to the phase-shift grating unit, and the third port is used to output the plurality of time-sequentially arranged Pulsed light of different wavelengths;
  • the phase-shift grating unit includes an optical fiber, and a plurality of reflection-type phase-shift gratings with different wavelengths of central windows are arranged on the optical fiber.
  • the laser further includes a first wavelength division multiplexer, wherein:
  • the first port of the first wavelength division multiplexer is connected to the output end of the pulse controller, the second port is connected to the phase-shift grating unit, and the third port is used to output the plurality of time-sequentially arranged Pulsed light of different wavelengths;
  • the phase-shift grating unit includes a plurality of optical fibers, each of which is respectively provided with a reflective phase-shift grating, and the central window wavelengths of the phase-shift gratings on each of the optical fibers are all different.
  • the laser further includes a first wavelength division multiplexer
  • the phase-shift grating unit includes a plurality of optical fibers, each optical fiber is provided with a transmissive phase-shift grating, and each of the optical fibers is provided with a transmissive phase-shift grating.
  • the central window wavelengths of the phase-shift gratings on the fiber are all different;
  • the first port of the first wavelength division multiplexer is connected to the output end of the pulse controller, and the second port is connected to one end of each of the optical fibers.
  • the laser further includes a signal amplifier, wherein:
  • the signal amplifier is used for amplifying the amplitudes of the multiple pulsed lights of different wavelengths and then outputting them.
  • the signal amplifier is an erbium-doped fiber amplifier or an ytterbium-doped fiber amplifier.
  • the pulse controller is an electro-optical modulator and/or an acousto-optical modulator.
  • the multi-wavelength laser provided in this embodiment for synchronous monitoring of ocean temperature and pressure uses a pulse controller to convert the broad-spectrum laser light output from the broad-spectrum laser source into broad-spectrum pulsed light, and then uses a phase shift
  • the grating unit will demodulate multiple pulsed lights with different wavelengths from the broad-spectrum pulsed light.
  • the above-mentioned pulsed light output by the laser is injected into the sensing fiber in seawater through the wavelength division multiplexer, and the scattered light is returned to the control demodulation module through the wavelength division multiplexer, and the control demodulation module demodulates the above-mentioned scattered light,
  • the dynamic pressure is analyzed, and the wavelength change is analyzed for the seawater temperature, so as to achieve simultaneous monitoring of the two.
  • the broad-spectrum laser source can be selected from a low-cost common broad-spectrum laser.
  • the phase-shift grating is used to realize the demodulation of the broad-spectrum laser. Due to its extremely narrow bandwidth, high-quality pulsed laser can be obtained. spectrum.
  • FIG. 1 is a schematic diagram of the basic structure of a first multi-wavelength laser provided by an embodiment of the present application
  • FIG. 2 is a schematic diagram of the basic structure of a second multi-wavelength laser provided by an embodiment of the present application
  • FIG. 3 is a schematic diagram of the basic structure of a third multi-wavelength laser provided in an embodiment of the present application.
  • FIG. 4 is a schematic diagram of the laser spectrum arranged in time series output by the multi-wavelength laser provided by the embodiment of the present application;
  • FIG. 5 is a schematic diagram of the basic structure of a continuous space monitoring device for ocean temperature and pressure according to an embodiment of the present application
  • FIG. 6 is a schematic diagram of the basic structure of a first control and demodulation module provided by an embodiment of the present application.
  • FIG. 7 is a schematic diagram of the basic structure of a second control and demodulation module provided by an embodiment of the present application.
  • FIG. 8 is a schematic diagram of a basic structure of a third control and demodulation module provided by an embodiment of the present application.
  • the multi-wavelength laser provided in this embodiment includes a broad-spectrum laser source, a pulse controller, and a phase-shift grating unit, wherein the pulse controller is used to convert the broad-spectrum laser light output by the broad-spectrum laser source into broad-spectrum pulse light, and the phase-shift grating unit It is used for demodulating a plurality of pulsed lights with different wavelengths from the broad-spectrum pulsed light.
  • phase shift grating in the phase shift grating unit can realize the reflection or transmission of laser light, and the bandwidth of its transmission spectrum and reflection spectrum is extremely narrow.
  • the above-mentioned demodulation method of the phase-shift grating pair and the laser is divided into a transmission-type phase-shift grating and a reflection-type phase-shift grating.
  • the broad-spectrum laser source, the pulse controller and the phase-shift grating unit in the multi-wavelength laser can have three different structural forms.
  • FIG. 1 is a schematic diagram of a basic structure of a first multi-wavelength laser provided by an embodiment of the present application.
  • the multi-wavelength laser includes a broad-spectrum laser source 101 , a pulse controller 102 , a first wavelength division multiplexer 103 and a phase shift grating unit 104 .
  • the output end of the broad-spectrum laser source 101 is connected to the input end of the pulse controller 102 for outputting broad-spectrum laser light with a small coherence length, for example, light with a line width of several hundred MHz or more, to the pulse controller 102 .
  • the pulse controller 102 can be an electro-optic modulator, an acousto-optic modulator, or a combination of the two, etc.
  • the pulse controller 102 converts the broad-spectrum laser light into a broad-spectrum pulse light based on the pulse control signal it receives, for example, a pulse control signal When the pulse controller 102 is at a low level, the pulse controller 102 does not output light, and when the pulse control signal is at a high level, the pulse controller 102 outputs light, thereby realizing the output of a broad-spectrum pulse signal.
  • the pulse control signal received by the pulse controller 102 may be controlled by the pulse control signal module. It should be noted that, in this embodiment, since the laser signal received by the pulse controller 102 is a broad-spectrum laser, the pulse signal outputted by the pulse controller 102 is called a broad-spectrum pulsed light.
  • the first port W1 of the first wavelength division multiplexer 103 is connected to the output end of the pulse controller 102 , and the second port W2 is connected to the phase shift grating unit 104 .
  • the broad-spectrum pulse light output by the pulse controller 102 passes through the first port W1 and the second port W2 of the first wavelength division multiplexer 103.
  • the phase-shift grating unit includes an optical fiber, and the optical fiber is provided with a plurality of central windows with different wavelengths. reflective phase-shift grating.
  • n phase-shift gratings are engraved on an erbium-doped fiber, and the central window wavelengths are respectively ⁇ 1 , ⁇ 2 , ⁇ 3 , ⁇ 4 , ⁇ 5 , ⁇ 6 whil ⁇ n-1 , ⁇ n , the broad-spectrum pulse light output by the pulse controller 102 enters the optical fiber after passing through the first wavelength division multiplexer 103, and then demodulates the pulse light with wavelength ⁇ 1 after passing through the PSFBG1, and passes through the first wavelength division multiplexer 103.
  • the second port W2 returns to its third port W3, and the light of other wavelengths is transmitted to PSFBG2 through the optical fiber between PSFBG1 and PSFBG2 (this embodiment is called a delay fiber), and after passing through PSFBG2, the pulse of wavelength ⁇ 2 is demodulated light, and returns to its third port W3 through the second port W2 of the first wavelength division multiplexer 103. Similarly, after the remaining PSFBG, the pulsed light of other wavelengths is demodulated, and then the different wavelengths arranged in time sequence are obtained.
  • the wavelength of the laser light spectrum, and by setting the length of the delay fiber between each PSFBG, the time interval between the pulsed light of each wavelength can be set.
  • this embodiment is further provided with an erbium-doped fiber amplifier 105, wherein the erbium-doped fiber amplifier One end of 105 is connected to the third port W3 of the first wavelength division multiplexer 103, and is used to amplify the amplitudes of multiple pulsed lights of different wavelengths output by the first wavelength division multiplexer 103 and output them.
  • erbium-doped fiber amplifier 105 is connected to the third port W3 of the first wavelength division multiplexer 103, and is used to amplify the amplitudes of multiple pulsed lights of different wavelengths output by the first wavelength division multiplexer 103 and output them.
  • Examples may also be other types of optical signal amplifiers, such as ytterbium-doped fiber amplifiers.
  • FIG. 2 is a schematic diagram of a basic structure of a second multi-wavelength laser provided in an embodiment of the present application.
  • the phase-shift grating unit 104 is composed of multiple fibers, each fiber is etched with a reflective phase-shift grating, and the phase-shift grating on the fiber is The wavelengths of the central windows of the gratings are different, and after being injected into each optical fiber through the second port W2 of the first wavelength division multiplexer 103, pulsed light of different wavelengths can be obtained, and by setting the length of the delay fiber in each optical fiber, Obtain laser spectra of different wavelengths arranged in time series.
  • FIG. 3 is a schematic diagram of the basic structure of a third multi-wavelength laser provided in an embodiment of the present application.
  • the main difference between this embodiment and the second multi-wavelength laser is that the phase-shift grating on the above-mentioned optical fiber is a transmissive phase-shift fiber, and further, the first wavelength division multiplexer 103 in this embodiment
  • the second port W2 is connected to one end of the phase-shift grating unit 104 , and the other end is connected to the input port of the erbium-doped fiber amplifier 105 .
  • FIG. 4 is a schematic diagram of time-sequentially arranged laser spectra output by a multi-wavelength laser according to an embodiment of the present application.
  • the optical pulse output by the multi-wavelength laser 10 outputs a wavelength sequence ⁇ ( ⁇ 1, ⁇ 2, ⁇ , ⁇ n-1, ⁇ n), which satisfies the following conditions:
  • Ln is the length of the nth delay fiber
  • W is the pulse width of the pulse control signal
  • ⁇ g is the transmission speed of light in the fiber medium.
  • the internal structure of the multi-wavelength laser 10 may also be a combined structure of any two or three of the foregoing embodiments.
  • FIG. 5 is a schematic diagram of the basic structure of a continuous space monitoring device for ocean temperature and pressure according to an embodiment of the present application.
  • the device includes a multi-wavelength laser 10 , a second wavelength division multiplexer 20 , a sensing fiber 30 and a control and demodulation module 40 .
  • the pulse control signal received by the pulse controller in the multi-wavelength laser 10 may be output by the control and demodulation module 40, and of course, another pulse control signal output module may also be provided.
  • the pulsed light of each wavelength output by the multi-wavelength laser 10 enters the sensing fiber 30 through the second wavelength division multiplexer 20 .
  • the sensing optical fiber 30 is arranged in the seawater, wherein the sensing optical fiber 30 can go straight to the seabed vertically.
  • the sensing fiber 30 is connected vertically to a deep water anchored mooring device on the seabed.
  • the above-mentioned deep-water anchoring and mooring device may use an anchor for mooring a ship, and the anchor is directly connected to the lower end of the sensing optical fiber 30 .
  • the sensing fiber 30 leads to the seabed vertically through the deepwater anchoring device, so the temperature distribution and pressure of each point on the sensing fiber 30 are the temperature field and pressure distribution vertically distributed along the depth of the ocean.
  • the sensing optical fiber 30 has strong anti-corrosion ability of seawater, anti-side pressure ability and tensile ability of seawater under the sea surface of hundreds of thousands of meters.
  • the pulsed light output by the multi-wavelength laser 10 adopted in this embodiment has a low coherence length.
  • this embodiment abandons the traditional method of interfering between backward Rayleigh scattered light and laser local oscillator light, and adopts The signal demodulation is realized by the method of back-scattered light self-interference.
  • the non-uniform fiber density caused by thermal disturbance and the impure fiber concentration are the main reasons for the non-uniform refractive index of the fiber, because the size of the non-uniform structure in the fiber is generally smaller than the wavelength of the incident light, Therefore, the Rayleigh scattering phenomenon occurs when the incident light is transmitted in the sensing fiber 30 .
  • the back Rayleigh scattered light power P BS (L) at the initial end L of the distance sensing fiber 30 is expressed as:
  • Equation (3) ⁇ g is the speed of light in the optical fiber transmission medium, [tau] is the pulse light is incident into the optical fiber width, C R is a backward Rayleigh scattering coefficient, i.e., the Rayleigh scattering to Rayleigh scattering power to the total Power ratio, ⁇ s is the Rayleigh attenuation coefficient, ⁇ is the fiber attenuation coefficient, and L is the distance from the initial end of the fiber to the scattering point.
  • Formula (3) is the scattered power at different positions on the sensing fiber 30. By monitoring the optical power, the distributed measurement of the entire fiber can be realized, and the continuous spatial measurement of parameters can be realized.
  • the back Rayleigh scattering curves measured at different times are the same; when the temperature on the sensing fiber changes, by finding the frequency of the incident light, it can be restored to the point before the temperature change The back Rayleigh scattering curve.
  • the back Rayleigh scattering light power Pa(v, z) on the sensing fiber is obtained through the incident frequency v of the multi-wavelength laser 10 .
  • Backward Rayleigh scattered light power Pb(v, z) is measured in the same way at time b. If the temperature on the sensing fiber does not change at time a and time b, then Pb(v,z) is the same as Pa(v,z); if the temperature or strain changes, find when the incident frequency reaches v+ ⁇ v, Pb(v + ⁇ v,z) is the same as Pa(v,z).
  • ⁇ v represents the frequency change of the incident frequency, which is related to the temperature change on the sensing fiber, which means that the temperature or strain change on the sensing fiber causes the back Rayleigh scattered light power Pb(v,z) to move in the frequency domain.
  • the temperature distribution information on the sensing fiber 30 can be obtained by calculating the peak frequency of the correlation function spectrum. That is, the control and demodulation module 40 can obtain the temperature distribution information on the sensing fiber 30 according to the change of the backward Rayleigh scattering light power of the pulsed light of each wavelength caused by the temperature change of each point on the sensing fiber 30, and then obtain the temperature distribution information on the sensing fiber 30.
  • the wavelength sequence of the backward Rayleigh scattered light enters the control demodulation module 40, and the phase of the fixed wavelength in the backward Rayleigh scattered light is demodulated, that is, the dynamic pressure of seawater can be analyzed.
  • this embodiment adopts a PGC (Phase Generated Carrier) or a 3 ⁇ 3 coupler phase demodulation scheme to demodulate the phase of the self-interference of the backward Rayleigh scattered light.
  • FIG. 6 is a schematic diagram of a basic structure of a first control and demodulation module provided by an embodiment of the present application. As shown in FIG. 6 , this embodiment adopts the PGC demodulation method based on the Michelson interferometer.
  • the module mainly includes a coupler 411 , a first interference arm 412 , a second interference arm 413 , Faraday rotating mirrors 414 / 415 , and a photodetector.
  • the controller 416 and the acquisition processing unit 417 wherein:
  • the first end of the coupler 411 is connected to the second port of the second wavelength division multiplexer 20 , and the second end is connected to one end of the first interference arm 412 and the second interference arm 413 respectively.
  • the first interference arm 412 and the second The other ends of the interference arm 413 are respectively connected with a Faraday rotating mirror 414 and 415 .
  • the first interference arm 412 is provided with a phase modulator 4121
  • the second interference arm 413 is provided with a phase matching loop 4131
  • the length L of the phase matching loop 4131 satisfies the following conditions: L ⁇ Lo/2, L o is
  • the phase matching ring 4131 can also be set on the first interference arm 412 .
  • the photodetector 416 is connected to the third end of the coupler 411 for receiving the back Rayleigh scattered interference light returned by the first interference arm 412 and the second interference arm 413, and according to the backward Rayleigh scattering interference light A corresponding electrical signal is generated.
  • the acquisition and processing unit 417 is connected to the photodetector 416, and is used for processing the electrical signal output by the photodetector 416, and demodulates the phase change of the pulsed light of one wavelength caused by the disturbance signal in the sensing fiber, so as to realize the seawater Pressure monitoring; in addition, according to the change of the back Rayleigh scattered light power of pulsed light of each wavelength caused by the temperature change, to realize the monitoring of seawater temperature.
  • the light intensity I on the photodetector 416 can be expressed as:
  • A is the average optical power output by the interferometer
  • B is the amplitude of the interference signal
  • B ⁇ A
  • ⁇ 1 is the visibility of the interference fringes
  • ⁇ (t) is the phase difference of the interferometer.
  • Ccos ⁇ 0 t is the phase carrier, C is the amplitude, and ⁇ 0 is the carrier frequency; Dcos ⁇ s t is the phase change caused by the disturbance signal of the sensing fiber 30, D is the amplitude, ⁇ s is the frequency of the sound field signal, and ⁇ (t) is the slow change of the initial phase caused by environmental disturbances.
  • the interferometer output detector signal I expanded by the Bessel function is used to multiply the fundamental frequency signal (amplitude is G) and the double frequency signal (amplitude is H), in order to overcome the fluctuation of the signal with the external interference signal.
  • the phenomenon of blanking and distortion, the differential cross-multiplication (DCM) is performed on the two signals, and the differential cross-multiplied signal is converted into
  • the signal obtained after integration contains the signal to be measured Dcos ⁇ s t and the external environment information.
  • the latter is usually a slow-varying signal, and the amplitude can be very large, which can be filtered by a high-pass filter, and the final output is:
  • FIG. 7 is a schematic diagram of a basic structure of a second control and demodulation module provided by an embodiment of the present application. As shown in FIG. 7 , this embodiment adopts a 3 ⁇ 3 coupler phase demodulation method based on a Michelson interferometer.
  • the module mainly includes a coupler 424 , a first interference arm 425 , a second interference arm 426 , and a Faraday rotating mirror 427 /428, a first photodetector 421, a second photodetector 422, a third photodetector 423, a second wavelength division multiplexer, and an acquisition processing unit 429.
  • the first end of the coupler 424 is connected to the third port of the second wavelength division multiplexer 20, and the second end is connected to one end of the first interference arm 425 and the second interference arm 426, respectively.
  • the first interference arm 425 and the second The other ends of the interference arms 426 are respectively connected with a Faraday rotating mirror 427/428.
  • a phase matching ring 4261 is provided on the second interference arm 426, and the length L of the phase matching ring 4261 satisfies the following conditions: L ⁇ Lo/2, L o is the coherence length of the pulsed light.
  • the phase matching ring can also be 4261 is provided on the first interference arm 425.
  • the first photodetector 421 , the second photodetector 422 and the third photodetector 423 are all connected to the coupler 424 for receiving the backward Rays returned by the first interference arm 425 and the second interference arm 426 .
  • Rayleigh scattering interference light is generated, and a corresponding electrical signal is generated according to the back Rayleigh scattering interference light.
  • the backward Rayleigh scattered light is incident on the port 2 of the coupler 424 through the circulator 20, and is split into two optical signals by the port 2 of the coupler 424.
  • One light enters the port 4 of the coupler 424 and passes through the first interference arm. 425 and Faraday rotating mirror 427 return to port 4 of coupler 424, and another beam of light enters port 6 of coupler 424 and returns to port 6 of coupler 424 through second interference arm 426 and Faraday rotating mirror 428, two beams of light
  • the beam is combined and interfered, and the back-scattered interference light enters the first photodetector 421 and the third photodetector 423 through the port 1 and port 3 of the coupler 424, and the back-scattered interference light passes through the Port 2 of the coupler 424 enters the second photodetector 422 after passing through the second wavelength division multiplexer 20 .
  • ⁇ (t) ⁇ (t)+ ⁇ (t);
  • D is the DC component of the interference signal;
  • I 0 is the amplitude of the AC component of the interference signal;
  • ⁇ (t) is the phase difference signal caused by the disturbance signal, rad;
  • ⁇ (t) is the phase difference signal caused by the environmental noise, rad.
  • the optical signals received by the three detectors are phase-demodulated by the acquisition and processing unit 429, and then the phase change of the pulsed light of one wavelength caused by the disturbance signal in the sensing fiber 30 is obtained; in addition, the acquisition and processing unit 429 is also used for the backward Rayleigh scattered light power change of pulsed light of each wavelength caused by temperature change.
  • FIG. 8 is a schematic diagram of a basic structure of a third control and demodulation module provided by an embodiment of the present application. As shown in FIG. 8 , this embodiment adopts the PGC phase demodulation method based on the Mach-Zehnder interferometer, and the module mainly includes a first interference arm 431 , a second interference arm 432 , a photodetector 433 and an acquisition processing unit 434 .
  • the third port of the second wavelength division multiplexer 20 is connected to one end of the first interference arm 431 and the second interference arm 432 respectively, and the other ends of the first interference arm 431 and the second interference arm 432 are respectively connected to the photodetector 433 .
  • a phase matching ring 4321 is provided on the second interference arm 432, and the length L of the phase matching ring 4321 satisfies the following conditions: L ⁇ L 0 , L o is the coherence length of the pulsed light.
  • the phase matching ring 4321 can also be provided on the first interference arm 431 .
  • the photodetector 433 is configured to receive the back Rayleigh scattered interference light output by the first interference arm 431 and the second interference arm 432, and generate a corresponding electrical signal according to the back Rayleigh scattered interference light.
  • the acquisition and processing unit 434 is connected to the photodetector 433, and is used for processing the electrical signal output by the photodetector to demodulate the phase change of the pulsed light of one wavelength caused by the disturbance signal in the sensing fiber, The back Rayleigh scattered light power of pulsed light of each wavelength changes due to temperature change.

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Abstract

本申请提供了一种用于海洋温度及压力同步监测的多波长激光器，利用脉冲控制器将宽谱激光源输出的宽谱激光转换为宽谱脉冲光，然后，利用相移光栅单元将从宽谱脉冲光中解调出多个不同波长的脉冲光。将激光器所输出的上述脉冲光经波分复用器射入海水中的传感光纤，散射光通过波分复用器返回控制解调模块，控制解调模块对上述利散射光进行解调，根据光信号的相位变化解析动态压力、波长变化解析海水温度，从而达到两者同时监测。本实施例提供的激光器，宽谱激光源选用低成本的普通宽谱激光器即可，同时，利用相移光栅实现宽谱激光的解调，由于其带宽极窄，进而可以获得高质量的脉冲激光光谱。

Description

一种用于海洋温度及压力同步监测的多波长激光器 技术领域
本申请涉及海洋环境监测技术领域，尤其涉及一种用于海洋温度及压力同步监测的多波长激光器。
背景技术
由于海洋面积广大又瞬息万变，它是影响全球气候、水、旱、台风等自然灾害的重要的因素，因此海洋环境对气象预报和灾害预警具有重大意义。其中，海水的温度和压力的测量对研究海洋学、海洋环境监测等有十分重要的意义，例如，在海洋科考、军事等领域，需要及时获得海温度剖面以及压力的动态变化。
目前，海洋温度和压力的监测装备多为电学设备，大多存在价格昂贵、体积大、布放困难、容易受电磁干扰等问题。并且，温度和压力多采用分立电子设备分别进行监测和信号处理，要实现海区大范围监控，需要大量传感器组合阵列，因此存在投资巨大、系统复杂且可靠性低、数据兼容与综合处理困难等问题。
鉴于此，为适应海洋规划发展需求，需大力开发数据兼容性强、成本低廉、结构紧凑、并满足高精度原位测量需求的海洋温度和压力监测装备。由于分布式光纤传感技术可以实现沿光纤长度方向分布的被测物理量连续传感、测量，能够集传感、传输功能于一体，不仅能够完成在整条光纤长度上的分布式环境参量的空间、时间多维分布状态信息的连续测量，还能将分布式的测量信息实时、无损地传输到信息处理中心，同时，基于分布式光纤传感技术的传感系统具有结构简单、使用方便、单位长度内信号获取成本低、性价比高等优点，因此，该技术应用于一种海洋温度及压力的连续空间监测。
在分布式光纤传感系统中，多波长的激光源是关键器件，而现有的多波长激光源价格居高不下，严重影响了分布式光纤传感的大规模推广，低价格、高性能的多波长激光源成为目前本领域技术人员亟待解决的问题。
发明内容
针对上述问题，本申请实施例提供了一种用于海洋温度及压力同步监测的多波长激光器。
本申请实施例提供的用于海洋温度及压力同步监测的多波长激光器，在第一种实现方式中，包括：
所述宽谱激光源，用于输出宽谱激光；
所述脉冲控制器用，于将所述宽谱激光源输出的宽谱激光转换为宽谱脉冲光；
所述相移光栅单元，用于从所述宽谱脉冲光中解调出按时序排列的多个不同波长的脉冲光。
在第二种实现方式中，所述激光器还包括第一波分复用器，其中：
所述第一波分复用器的第一端口与所述脉冲控制器的输出端连接、第二端口与所 述相移光栅单元连接、第三端口用于输出所述按时序排列的多个不同波长的脉冲光；
所述相移光栅单元包括一根光纤，所述光纤上设置有多个中心窗口波长不同的反射式相移光栅。
在第三种实现方式中，所述激光器还包括第一波分复用器，其中：
所述第一波分复用器的第一端口与所述脉冲控制器的输出端连接、第二端口与所述相移光栅单元连接、第三端口用于输出所述按时序排列的多个不同波长的脉冲光；
所述相移光栅单元包括多根光纤，各所述光纤上分别设置有一个反射式相移光栅，各所述光纤上的相移光栅的中心窗口波长均不相同。
在第四种实现方式中，所述激光器还包括第一波分复用器，所述相移光栅单元包括多根光纤，各所述光纤上分别设置有一个透射式相移光栅，各所述光纤上的相移光栅的中心窗口波长均不相同；
所述第一波分复用器的第一端口与所述脉冲控制器的输出端连接、第二端口与各所述光纤的一端连接。
在第五种实现方式中，所述激光器还包括信号放大器，其中：
所述信号放大器，用于将所述多个不同波长的脉冲光进行幅值放大后输出。
在第六种实现方式中，所述信号放大器为掺铒光纤放大器或掺镱光纤放大器。
在第七种实现方式中，所述脉冲控制器为电光调制器和/或声光调制器。
由上述实施例可见，本实施例提供的用于海洋温度及压力同步监测的多波长激光器，利用脉冲控制器将宽谱激光源输出的宽谱激光转换为宽谱脉冲光，然后，利用相移光栅单元将从宽谱脉冲光中解调出多个不同波长的脉冲光。将激光器所输出的上述脉冲光经波分复用器射入海水中的传感光纤，散射光通过波分复用器返回控制解调模块，控制解调模块对上述利散射光进行解调，根据光信号的相位变化解析动态压力、波长变化解析海水温度，从而达到两者同时监测。本实施例提供的激光器，宽谱激光源选用低成本的普通宽谱激光器即可，同时，利用相移光栅实现宽谱激光的解调，由于其带宽极窄，进而可以获得高质量的脉冲激光光谱。
附图说明
为了更清楚地说明本发明的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，显而易见地，对于本领域普通技术人员而言，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1为本申请实施例提供的第一种多波长激光器的基本结构示意图；
图2为本申请实施例提供的第二种多波长激光器的基本结构示意图；
图3为本申请实施例提供的第三种多波长激光器的基本结构示意图；
图4为本申请实施例提供的多波长激光器输出的按时序排列的激光光谱的示意图；
图5为本申请实施例提供的一种海洋温度及压力的连续空间监测装置的基本结构示意图；
图6为本申请实施例提供的第一种控制解调模块的基本结构示意图；
图7为本申请实施例提供的第二种控制解调模块的基本结构示意图；
图8为本申请实施例提供的第三种控制解调模块的基本结构示意图。
具体实施方式
这里将详细地对示例性实施例进行说明，其示例表示在附图中。下面的描述涉及附图时，除非另有表示，不同附图中的相同数字表示相同或相似的要素。以下示例性实施例中所描述的实施方式并不代表与本发明相一致的所有实施方式。相反，它们仅是与如所附权利要求书中所详述的、本发明的一些方面相一致的装置和方法的例子。
本实施例提供的多波长激光器包括宽谱激光源、脉冲控制器和相移光栅单元，其中，脉冲控制器用于将宽谱激光源输出的宽谱激光转换为宽谱脉冲光，相移光栅单元用于将从所述宽谱脉冲光中解调出多个不同波长的脉冲光。
相移光栅单元中的相移光栅(PSFBG,Phase Shifted Fiber Bragg Grating)，可以实现激光的反射或者透射，并且其透射谱、反射谱的带宽极窄。本实施将上述相移光栅对与激光的解调方式，将光栅光纤分为透射式相移光栅和反射式相移光栅。基于上述相移光栅的类型，多波长激光器中的宽谱激光源、脉冲控制器以及相移光栅单元可以有三种不同的结构形式。
图1为本申请实施例提供的第一种多波长激光器的基本结构示意图。如图1所示，多波长激光器包括宽谱激光源101、脉冲控制器102、第一波分复用器103和相移光栅单元104。
其中，宽谱激光源101的输出端与脉冲控制器102的输入端连接，用于向脉冲控制器102输出相干长度小的宽谱激光，例如，线宽为几百MHz以上的光。脉冲控制器102可以是电光调制器、声光调制器或者两者的组合等，脉冲控制器102基于其接收的脉冲控制信号，将该宽谱激光转换为宽谱脉冲光，例如，脉冲控制信号为低电平时，脉冲控制器102不输出光，脉冲控制信号为为高电平时，脉冲控制器102输出光，进而实现宽谱脉冲信号的输出。其中，脉冲控制器102所接收的脉冲控制信号可以脉冲控制信号模块控制。需要说明的是，本实施例中，由于脉冲控制器102接收的激光信号为宽谱激光，所以将其输出的脉冲信号称为宽谱脉冲光。
第一波分复用器103的第一端口W1与脉冲控制器102的输出端连接、第二端口W2与相移光栅单元104连接。脉冲控制器102输出的宽谱脉冲光以经过第一波分复用器103的第一端口W1和第二端口W2，相移光栅单元包括一根光纤，光纤上设置有多个中心窗口波长不同的反射式相移光栅。例如，本实施例在一根掺铒光纤上刻制n个相移光栅，中心窗口波长分别为λ 1、λ 2、λ 3、λ 4、λ 5、λ 6……λ n-1、λ n，脉冲控制器102输出的宽谱脉冲光经第一波分复用器103后，进入光纤，经过PSFBG1后解调出波长λ 1的脉冲光，并经第一波分复用器103的第二端口W2返回至其第三端口W3，其它波长的光经过PSFBG1与PSFBG2之间的光纤(本本实施例称其为延时光纤)传输至PSFBG2，经过PSFBG2后解调出波长λ 2的脉冲光，并经第一波分复用器103的第二端口W2返回至其第三端口W3，同理，经剩余的PSFBG后，解调出其它波长的脉冲光，进而得到按时序排列的不同波长的激光光谱，并且，通过设置各PSFBG之间的延时光纤的长度，便可以设置各波长的脉冲光之间的时间间隔。
进一步的，为对由第一波分复用器103的第三端口W3输出的光信号进行放大，如图2所示，本实施例还设置有掺铒光纤放大器105，其中，掺铒光纤放大器105一端与第一波分复用器103的第三端口W3连接，用于将第一波分复用器103输出的多个不 同波长的脉冲光进行幅值放大后输出，当然，在其它实施例也可以是其它类型的光信号放大器、如掺镱光纤放大器。
图2为本申请实施例提供的第二种多波长激光器的基本结构示意图。如图2所示，本实施例与上述多波长激光器的主要区别在于，相移光栅单元104由多根光纤组成，每根光纤上刻蚀有一个反射式相移光栅，并且光纤上的相移光栅的中心窗口波长不同，进而经第一波分复用器103的第二端口W2射入至各光纤后，可以得到不同波长的脉冲光，并且通过设置各根光纤中延时光纤的长度，得到按时序排列的不同波长的激光光谱。
图3为本申请实施例提供的第三种多波长激光器的基本结构示意图。如图3所示，本实施例与第二种多波长激光器的主要区别在于上述光纤上的相移光栅为透射式相移光纤，进而，本实施例中第一波分复用器103的第二端口W2与相移光栅单元104的一端连接、另一端与掺铒光纤放大器105的输入端口连接。
图4为本申请实施例提供的多波长激光器输出的按时序排列的激光光谱的示意图。如图4所示，多波长激光器10所输出的光脉冲在时间序列T(t1，t2，……，tn-1，tn)内输出波长序列λ(λ1，λ2，……，λn-1，λn)，满足如下条件：
t n-t n-1＝L n/v g(n≥2)       (1)
t n-t 1＝W          (2)
其中：Ln是第n个延时光纤的长度，W为脉冲控制信号的脉宽，υ g为光在光纤介质中的传输速度。
需要说明的是，在其它实施例中多波长激光器10的内部结构还可以是上述任意两种或三种实施方式的组合结构。
基于上述多波长激光器，本实施例还提供了海洋温度及压力的连续空间监测装置。图5为本申请实施例提供的一种海洋温度及压力的连续空间监测装置的基本结构示意图。如图5所示，该装置包括多波长激光器10、第二波分复用器20、传感光纤30和控制解调模块40。多波长激光器10中的脉冲控制器所接收的脉冲控制信号可以由控制解调模块40输出，当然，也可以另设置一个脉冲控制信号输出模块。
多波长激光器10输出的各波长的脉冲光经过第二波分复用器20进入传感光纤30。传感光纤30设置在海水内，其中，传感光纤30可以垂直直通海底。传感光纤30垂直连接至海床上的深水锚定系留装置。上述深水锚定系留装置可以使用船舶停泊用的锚，将锚直接连接在传感光纤30的下端。
该传感光纤30通过深水锚定系留装置垂直地通向海底，因而传感光纤30上各点的温度分布和压力也就是海洋沿纵深垂直分布的温度场和压力分布。该传感光纤30具有很强的抗海水腐蚀能力、抗十几万米海面下的海水侧压能力和抗拉能力。
进一步的，本实施例采用的多波长激光器10所输出的脉冲光相干长度低，为了实现干涉调整解调，本实施例摒弃传统的后向瑞利散射光与激光本振光干涉的方法，采用后向瑞利散射光自干涉的方法实现信号解调。
热扰动导致光纤密度的不均匀以及光纤浓度不纯净(例如浓度不均匀的氧化物)两种情况是造成光纤折射率不均匀的主要原因，因为光纤中的不均匀结构尺寸一般小于入射光波长，所以入射光在传感光纤30中传输时会产生瑞利散射现象。
设入射到光纤中的脉冲光的功率为P 0，距离传感光纤30初始端L处的后向瑞利散射光功率P BS(L)表达式为：
Figure PCTCN2020100403-appb-000001
公式(3)中：υ g为光在光纤介质中的传输速度，τ为入射到光纤中脉冲光宽度，C R为后向瑞利散射系数，即后向瑞利散射功率与总瑞利散射功率之比，α s为瑞利衰减系数，α为光纤衰减系数，L为从光纤初始端到散射点的距离。
公式(3)是传感光纤30上不同位置处的散射功率,通过监测光功率就可以实现对整个光纤的分布式测量，即可实现参量的连续空间测量。
当传感光纤上的温度没有变化时，不同时刻测得的后向瑞利散射曲线是相同的；当传感光纤上的温度有变化时，通过查找入射光频率中，可以恢复到温度变化前的后向瑞利散射曲线。
假设传感光纤30上的初始a时刻的温度为25℃，通过多波长激光器10入射频率v，得到传感光纤上的后向瑞利散射光功率Pa(v,z)。在b时刻以相同方法测量得到后向瑞利散射光功率Pb(v,z)。如果a时刻和b时刻传感光纤上的温度没有变化，则Pb(v,z)与Pa(v,z)相同；如果温度或应变发生变化，查找入射频率到达v+Δv时，Pb(v+Δv,z)与Pa(v,z)相同。Δv表示入射频率的频率变化量，与传感光纤上温度变化有关，这意味着传感光纤上温度或应变变化引起后向瑞利散射光功率Pb(v,z)在频域上的移动。
综上所述，对a、b时刻产生的后向瑞利散射光功率Pa(v,z)与Pb(v,z)进行相关处理，相关函数取最大值时对应入射光频率的变化量。因此，通过计算相关函数频谱的峰值频率可以获取传感光纤30上温度的分布信息。即控制解调模块40根据传感光纤30上各点的温度变化所引起的各波长的脉冲光的后向瑞利散射光功率变化，可以获得传感光纤30上温度的分布信息，进而可以获得海洋沿纵深分布的温度场。
同时，后向瑞利散射光波长序列进入到控制解调模块40，解调出后向瑞利散射光中固定波长的相位，即可以解析海水动态压力大小。其中，根据不同形式的控制解调模块，本实施例采用PGC(相位载波，Phase Generated Carrier)或者3×3耦合器相位解调方案，解调出后向瑞利散射光自干涉的相位。
图6为本申请实施例提供的第一种控制解调模块的基本结构示意图。如图6所示，本实施例采用基于迈克尔逊干涉仪的PGC解调方式，该模块主要包括耦合器411、第一干涉臂412、第二干涉臂413、法拉第旋转镜414/415、光电探测器416以及采集处理单元417，其中：
耦合器411的第一端与第二波分复用器20的第二端口连接、第二端分别与第一干涉臂412和第二干涉臂413的一端连接，第一干涉臂412和第二干涉臂413另一端分别连接一个法拉第旋转镜414、415。另外，在第一干涉臂412上设有相位调制器4121，在第二干涉臂413上设有相位匹配环4131，相位匹配环4131的长度L满足下面条件：L≤Lo/2，L o是脉冲光的相干长度，当然，也可以将相位匹配环4131设置在第一干涉臂412上。
光电探测器416与所述耦合器411的第三端连接，用于接收述第一干涉臂412和第二干涉臂413返回的后向瑞利散射干涉光，并根据后向瑞利散射干涉光生成相应的 电信号。采集处理单元417与光电探测器416连接，用于对光电探测器416输出的电信号进行处理，解调出传感光纤中的扰动信号所引起的一个波长的脉冲光的相位变化，以实现海水压力的监测；另外，还会根据温度变化引起的各波长的脉冲光的后向瑞利散射光功率变化，以实现海水温度的监测。
具体的，对于相位的解调，根据光的相干原理，光电探测器416上的光强I可表示为：
I＝A+BcosΦ(t)            (4)
式(4)中：A是干涉仪输出的平均光功率，B是干涉信号幅值，B＝κA，κ≤1为干涉条纹可见度。Φ(t)是干涉仪的相位差。设
Figure PCTCN2020100403-appb-000002
则式(2)可写为：
Figure PCTCN2020100403-appb-000003
在式(5)中Ccosω 0t是相位载波，C是幅值，ω 0是载波频率；
Figure PCTCN2020100403-appb-000004
Figure PCTCN2020100403-appb-000005
Dcosω st是传感光纤30扰动信号引起的相位变化,D是幅值，ω s是声场信号频率,Ψ(t)是环境扰动等引起的初始相位的缓慢变化。将式(5)用Bessel函数展开得：
Figure PCTCN2020100403-appb-000006
式(6)中J n(m)是m调制深度下的n阶Bessel函数值，分别令k＝0和1，便可以得到极品信号和二倍频信号。
利用Bessel函数展开后的干涉仪输出探测器信号I进行基频信号(幅值是G)、二倍频信号(幅值是H)相乘，为了克服信号随外部的干扰信号的涨落而出现的消隐和畸变现象,对两路信号进行了微分交叉相乘(DCM)，微分交叉相乘后的信号经过差分放大、积分运算处理后转换为
Figure PCTCN2020100403-appb-000007
将
Figure PCTCN2020100403-appb-000008
代入式(5)，可得：
B 2GHJ 1(C)J 2(C)[Dcosω st+Ψ(t)]          (8)
可得，积分后得到的信号包含了待测信号Dcosω st和外界的环境信息.，后者通常是个慢变信号，且幅度可以很大，可通过高通滤波器加以滤除，最后输出为：
B 2GHJ 1(C)J 2(C)Dcosω st              (9)
由式(9)可以求解出传感光纤30扰动信号引起的相位变化的Dcosω st信号。
图7为本申请实施例提供的第二种控制解调模块的基本结构示意图。如图7所示，本实施例采用基于迈克尔逊干涉仪的3×3耦合器相位解调方式，该模块主要包括耦合器424、第一干涉臂425、第二干涉臂426、法拉第旋转镜427/428、第一光电探测器421、第二光电探测器422、第三光电探测器423、第二波分复用器以及采集处理单元429。
耦合器424的第一端与第二波分复用器20的第三端口连接、第二端分别与第一干涉臂425和第二干涉臂426的一端连接，第一干涉臂425和第二干涉臂426另一端分 别连接一个法拉第旋转镜427/428。另外，在第二干涉臂426上设有相位匹配环4261，相位匹配环4261的长度L满足下面条件：L≤Lo/2，L o是脉冲光的相干长度，当然，也可以将相位匹配环4261设置在第一干涉臂425上。
第一光电探测器421、第二光电探测器422和第三光电探测器423均与所述耦合器424连接，用于接收所述第一干涉臂425和第二干涉臂426返回的后向瑞利散射干涉光，并根据所述后向瑞利散射干涉光生成相应的电信号。
后向瑞利散射光经过环形器20入射到耦合器424的端口2，由耦合器424的端口2分束分为两路光信号，一路光进入耦合器424的端口4，经过第一干涉臂425和法拉第旋转镜427返回耦合器424的端口4，另一束光进入到耦合器424的端口6经第二干涉臂426和法拉第旋转镜428后返回到耦合器424的端口6，两束光在耦合器424处合束干涉，后向瑞利散射干涉光经耦合器424的端口1、端口3进入到第一光电探测器421和第三光电探测器423，后向瑞利散射干涉光经耦合器424的端口2经过第二波分复用器20后进入到第二光电探测器422。
其中，三个探测器获取到的光强表达式为：
I p＝D+I 0cos[φ(t)-(p-1)×(2π/3)]，p＝1,2,3        (10)
在式(10)中，Φ(t)＝φ(t)+ψ(t)；D为干涉信号直流分量；I 0为干涉信号交流分量幅值；p为探测器接收光信号序列号，p＝1，2，3；φ(t)为扰动信号引起的相位差信号，rad；ψ(t)为环境噪声引起的相位差信号，rad。
然后，利用采集处理单元429对三个探测器所接收的光信号进行相位解调，进而得出传感光纤30中的扰动信号所引起的一个波长的脉冲光的相位变化；另外，采集处理单元429还用于温度变化引起的各波长的脉冲光的后向瑞利散射光功率变化。
图8为本申请实施例提供的第三种控制解调模块的基本结构示意图。如图8所示，本实施例采用基于马赫曾德干涉仪的PGC相位解调方式，该模块主要包括第一干涉臂431、第二干涉臂432、光电探测器433以及采集处理单元434。
第二波分复用器20的第三端口分别与第一干涉臂431和第二干涉臂432的一端连接，第一干涉臂431和第二干涉臂432的另一端分别与光电探测器433连接。另外，在第二干涉臂432上设有相位匹配环4321，相位匹配环4321的长度L满足下面条件：L≤L 0，L o是脉冲光的相干长度，当然，也可以将相位匹配环4321设置在第一干涉臂431上。
光电探测器433用于接收第一干涉臂431和第二干涉臂432输出的后向瑞利散射干涉光，并根据后向瑞利散射干涉光生成相应的电信号。采集处理单元434与光电探测器433连接，用于对所述光电探测器输出的电信号进行处理，解调出所述传感光纤中的扰动信号所引起的一个波长的脉冲光的相位变化、温度变化引起的各波长的脉冲光的后向瑞利散射光功率变化。
本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。
本领域技术人员在考虑说明书及实践这里发明的发明后，将容易想到本发明的其它实施方案。本申请旨在涵盖本发明的任何变型、用途或者适应性变化，这些变型、用途或者适应性变化遵循本发明的一般性原理并包括本发明未发明的本技术领域中的 公知常识或惯用技术手段。说明书和实施例仅被视为示例性的，本发明的真正范围和精神由下面的权利要求指出。
应当理解的是，本发明并不局限于上面已经描述并在附图中示出的精确结构，并且可以在不脱离其范围进行各种修改和改变。本发明的范围仅由所附的权利要求来限制。

Claims (7)

  1. 一种用于海洋温度及压力同步监测的多波长激光器，其特征在于，包括宽谱激光源、脉冲控制器和相移光栅单元，其中：
    所述宽谱激光源，用于输出宽谱激光；
    所述脉冲控制器用，于将所述宽谱激光源输出的宽谱激光转换为宽谱脉冲光；
    所述相移光栅单元，用于从所述宽谱脉冲光中解调出按时序排列的多个不同波长的脉冲光。
  2. 根据权利要求1所述的用于海洋温度及压力同步监测的多波长激光器，其特征在于，所述激光器还包括第一波分复用器，其中：
    所述第一波分复用器的第一端口与所述脉冲控制器的输出端连接、第二端口与所述相移光栅单元连接、第三端口用于输出所述按时序排列的多个不同波长的脉冲光；
    所述相移光栅单元包括一根光纤，所述光纤上设置有多个中心窗口波长不同的反射式相移光栅。
  3. 根据权利要求1所述的用于海洋温度及压力同步监测的多波长激光器，其特征在于，所述激光器还包括第一波分复用器，其中：
    所述第一波分复用器的第一端口与所述脉冲控制器的输出端连接、第二端口与所述相移光栅单元连接、第三端口用于输出所述按时序排列的多个不同波长的脉冲光；
    所述相移光栅单元包括多根光纤，各所述光纤上分别设置有一个反射式相移光栅，各所述光纤上的相移光栅的中心窗口波长均不相同。
  4. 根据权利要求1所述的用于海洋温度及压力同步监测的多波长激光器，其特征在于，所述激光器还包括第一波分复用器，所述相移光栅单元包括多根光纤，各所述光纤上分别设置有一个透射式相移光栅，各所述光纤上的相移光栅的中心窗口波长均不相同；
    所述第一波分复用器的第一端口与所述脉冲控制器的输出端连接、第二端口与各所述光纤的一端连接。
  5. 根据权利要求1至4任一所述的用于海洋温度及压力同步监测的多波长激光器，其特征在于，所述激光器还包括信号放大器，其中：
    所述信号放大器，用于将所述多个不同波长的脉冲光进行幅值放大后输出。
  6. 根据权利要求5所述的用于海洋温度及压力同步监测的多波长激光器，其特征在于，所述信号放大器为掺铒光纤放大器或掺镱光纤放大器。
  7. 根据权利要求1所述的用于海洋温度及压力同步监测的多波长激光器，其特征在于，所述脉冲控制器为电光调制器和/或声光调制器。
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