WO2016127323A1 - 一种基于激光器的传感器 - Google Patents

一种基于激光器的传感器 Download PDF

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Publication number
WO2016127323A1
WO2016127323A1 PCT/CN2015/072694 CN2015072694W WO2016127323A1 WO 2016127323 A1 WO2016127323 A1 WO 2016127323A1 CN 2015072694 W CN2015072694 W CN 2015072694W WO 2016127323 A1 WO2016127323 A1 WO 2016127323A1
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segment
common
light
unit
detection
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PCT/CN2015/072694
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English (en)
French (fr)
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文侨
梁国文
李冀
牛憨笨
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深圳大学
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Priority to PCT/CN2015/072694 priority Critical patent/WO2016127323A1/zh
Priority to US15/140,067 priority patent/US9837785B2/en
Publication of WO2016127323A1 publication Critical patent/WO2016127323A1/zh

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    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08059—Constructional details of the reflector, e.g. shape
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10061—Polarization control
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
    • G01B9/02002—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies
    • G01B9/02003—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies using beat frequencies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02015—Interferometers characterised by the beam path configuration
    • G01B9/02023—Indirect probing of object, e.g. via influence on cavity or 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06791—Fibre ring lasers
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08013—Resonator comprising a fibre, e.g. for modifying dispersion or repetition rate
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/083—Ring lasers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/70—Using polarization in the interferometer
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06712—Polarising fibre; Polariser
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/082—Construction or shape of optical resonators or components thereof comprising three or more reflectors defining a plurality of resonators, e.g. for mode selection or suppression

Definitions

  • the invention belongs to the field of optical sensing technology, and in particular relates to a laser based sensor.
  • laser phase type interferometry when measuring small changes in physical quantities such as length, temperature, refractive index, pressure, etc., laser phase type interferometry is usually used for measurement.
  • Optical sensors based on Mach-Zehnder interferometer are a common use of laser phase type interferometry. The principle of measuring the sensor is to divide the laser output from the laser into two beams and enter the two arms of the interferometer. The two paths of light pass through different transmission paths and then merge to form an interference. The detector detects the phase of the two beams. Poor, and thus determine the physical quantity to be measured.
  • the Mach-Zehnder interferometer can measure physical quantities such as strain and temperature, and is an important physical basis for many sensors.
  • this sensor detects the phase difference between the two lasers, and its detection accuracy and sensitivity are still limited. It is necessary to provide a new type of high-precision, high-sensitivity optical sensor.
  • the present invention is achieved by a laser-based sensor including a pump source, a common section, and a reference section and a detection section connected in parallel between both ends of the common section, the common section being provided with a gain medium,
  • the detecting section is provided with a sensing element capable of causing an optical path difference;
  • One end of the reference segment and the detecting segment are connected to the common segment through a first polarization splitting unit, and One end is connected to the common segment by a second polarization splitting unit;
  • the common segment and the reference segment constitute a first laser cavity for transmitting the first linearly polarized light
  • the common segment and the detection segment constitute a second transmission of the second linearly polarized light
  • Two laser resonators are connected to the common segment through a first polarization splitting unit, and One end is connected to the common segment by a second polarization splitting unit;
  • the common segment is provided with an output unit or each of the reference segment and the detection segment is provided with an output unit.
  • the output unit is connected to the photodetector through the light combining unit, and the laser light is output from the output unit, and is transmitted to the device after being combined.
  • a photodetector is further provided; and a polarization state rotation unit for changing a polarization state of the first linearly polarized light and the second linearly polarized light to be uniform is further provided between the light combining unit and the output unit.
  • the sensor provided by the invention comprises two laser resonators with different polarization states, the two laser resonators share a common segment containing the same gain medium, and a sensing element capable of causing an optical path difference is disposed in the detection section through the sensing
  • the component senses the measured physical quantity, which causes the laser frequency of the detection section to change, so that the two lasers generate a frequency difference.
  • the two different frequencies of the laser generate heterodyne interference, and the detected frequency difference determines the size of the measured physical quantity, and The frequency of the oscillation is very sensitive to the change of the optical path of the cavity.
  • the detection sensitivity and accuracy of the sensor are much higher than the traditional phase difference-based sensor, and the two resonators of the sensor have a common path of light, and the external environment leads to the public.
  • the change of the segment causes the frequency changes of the two lasers to be basically the same, so the detection frequency difference can offset the change, so the sensor has strong anti-interference ability and is suitable for measuring small changes of various physical quantities.
  • FIG. 1 is a schematic structural view of a laser-based sensor according to a first embodiment of the present invention
  • FIG. 2 is another schematic structural diagram of a laser-based sensor according to a first embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a laser-based sensor according to a second embodiment of the present invention.
  • FIG. 4 is a schematic structural diagram of a laser-based sensor according to a third embodiment of the present invention.
  • FIG. 5 is a schematic structural diagram of a laser-based sensor according to a fourth embodiment of the present invention.
  • FIG. 6 is another schematic structural diagram of a laser-based sensor according to a fourth embodiment of the present invention.
  • FIG. 7 is a schematic structural diagram of a laser-based sensor according to a fifth embodiment of the present invention.
  • FIG. 8 is a schematic structural diagram of a laser-based sensor according to a sixth embodiment of the present invention.
  • an embodiment of the present invention provides a laser-based sensor, including a pump source 01, a common segment 02, and a reference segment 03 and a detection segment 04 that are connected in parallel between two ends of the common segment 02,
  • the common section 02 is provided with a gain medium 05
  • the detecting section 04 is provided with a sensing element 06 which can cause an optical path difference.
  • the incident light can be divided into first linearly polarized light and second linearly polarized light having different polarization directions, and the common segment 02 and the reference segment 03 constitute a first laser cavity for transmitting the first linearly polarized light, and the common segment 02 and the detection segment 04 constitute a second laser cavity for transmitting the second linearly polarized light; the common section 02 is provided with an output unit 09, or the reference section 03 and the detection section 04 are respectively provided with an output unit 09, and the output unit 09 is connected to the photodetector 11 through the light combining unit 10, A polarization state rotation unit 12 for making the polarization states of the first linearly polarized light and the second linearly polarized light become uniform is further provided between the light combining unit 10 and the output unit
  • the laser light is output from the output unit 09.
  • One of the linearly polarized lights passes through the polarization state rotating unit 12, and the polarization direction thereof is the same as the other linearly polarized light.
  • the two linearly polarized lights having the same polarization state are combined by the light combining unit 10 and transmitted to the photoelectric device.
  • the detector 11 performs interference detection.
  • the first embodiment of the present invention records the first linearly polarized light as P light and the second linearly polarized light as S light, that is, P light is used as reference light, and S light is used as detection light.
  • the working principle of the sensor is that the pump source 01 sends the pump light into the common section 02, and the excitation medium 05 is excited to generate excitation light to both sides, and the excitation light is divided into S light and P light by the first polarization splitting unit 07, and The P light enters the reference segment 03, and the S light enters the detecting segment 04, and the measured physical quantity acts on the sensing element 06 of the detecting segment 04, so that the cavity length of the second resonant cavity changes, thereby changing the frequency of the S light, due to The length of the first resonant cavity is not changed, and thus the P light frequency is not changed, such that the laser light in the first laser cavity and the second laser cavity generates a frequency associated with the change in the optical path caused by the outside through the sensing element 06.
  • the lasers of different frequencies in the two resonant cavities are outputted by the output unit 09 and heterodyne interference, and then the interference pattern is detected by the photodetector photodetector, thereby obtaining the frequency difference of the two lasers, according to which the frequency difference can be determined Measure the size of the physical quantity.
  • the laser frequency is In the second laser cavity, the laser frequency is Where C is the speed of light, the longitudinal modulus q is an integer, and L 1 and L 2 are the optical paths of the first and second laser resonators, respectively.
  • L is the average value of the optical paths of the first and second laser resonators
  • ⁇ is the average value of the frequencies of the first laser cavity and the second laser cavity.
  • ⁇ is the wavelength of the laser. Since the formula, the speed of light C in the numerator is a large value, and ⁇ in the denominator is a small amount. Therefore, when the optical path L changes slightly, since the numerator is a large value and the denominator is a small value, the frequency difference ⁇ also changes greatly.
  • the senor is significantly higher than the conventional sensor (Mach) - Zender interferometer, etc.) sensitivity and detection accuracy, and the two resonant cavities of the sensor have a common path of light, and the external environment causes the change of the common segment 02 to cause the frequency changes of the two lasers to be substantially the same, so the detection frequency
  • the difference can offset this change, so the sensor is less affected by the external environment and has strong anti-interference ability, which is suitable for measuring small changes of various physical quantities.
  • the first laser cavity and the second laser cavity in the embodiment of the invention may be either a straight cavity structure or an annular cavity structure.
  • the present invention will be described in detail below in conjunction with specific embodiments:
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the first laser cavity and the second laser cavity of this embodiment are annular cavity structures.
  • the common section 02, the reference section 03 and the detection section 04 of the sensor are all transmitted by polarization-maintaining fibers, the common section 02 includes a common optical fiber 021, the reference section 03 includes a reference optical fiber 031, and the detection section 04 includes a detection optical fiber 041, which can cause The optical path difference sensing element 06 is disposed on the detecting fiber 041.
  • Both ends of the common optical fiber 021 are connected to the detecting optical fiber 041 and the reference optical fiber 031 through the first polarization splitting unit 07 and the second polarization splitting unit 08 (this embodiment employs a polarization coupler as a polarization splitting unit).
  • a wavelength division multiplexer 15 is disposed on the common optical fiber 021, and an output unit 09 is respectively disposed on the detecting optical fiber 041 and the reference optical fiber 031, and specifically, an output coupler is connected, and the two output couplers are connected to a light combining unit 10, and the light is combined.
  • the unit 10 is connected to the photodetector 11.
  • a polarization state rotation unit 12 is provided between an output coupler and the light combining unit 10.
  • the working principle of the sensor is that the pump light enters the common optical fiber 021 via the wavelength division multiplexer 15, and the excitation gain medium 05 emits excitation light to both sides, wherein the counterclockwise excitation light is divided by the first polarization beam splitting unit 07.
  • S light and P light P light enters reference fiber 031
  • S light enters detection fiber 041
  • clockwise excitation light passes through second polarization beam splitting unit 08 and is divided into S light and P light, wherein P light enters reference fiber 031,
  • S The light enters the detecting fiber 041 such that two beams of opposite directions are transmitted in the first laser cavity and the second laser cavity, and two S lights of opposite directions are transmitted in the reference fiber 031, and are transmitted in the detecting fiber 041.
  • the sensor of such a structure can be detected by the interference of the S light and the P light in the opposite direction, or can be detected by the interference of the S light and the P light in the same direction, and is mainly determined according to the output mode.
  • two output couplers can be used as the output unit, so that one output coupler outputs clockwise S light (or P light), and the other output coupler outputs counterclockwise P light (or S light). ), at this time, interference occurs by two laser beams transmitted in the reverse direction.
  • the output unit 09 can also be disposed on the common optical fiber 021. Specifically, it can be a coupler with four ports or a three-port coupler, as shown in FIG. 2, in the common optical fiber.
  • An output coupler is disposed on the 021, the coupler has an output end connected to the third polarization splitting unit 13, splitting the beam into S light and P light, and setting a polarization rotation on the optical path of the S light or the P light.
  • the unit 12 changes the polarization states of the two beams to be uniform, and then inputs them to the photodetector 11 through the combining unit 10.
  • the common optical fiber 021 serves as the common section 02 of the two resonant cavities, because the lasers in the two resonant cavities generate a certain mutual coupling in the common section 02, for example, using a reverse laser to dry.
  • the lasers of the clockwise cavity and the counterclockwise cavity are transmitted through this section.
  • backscattering is inevitable, and the backscattered laser must participate in the other laser, so that the two-arm laser
  • the backscattered light participates in the optical path transmission of the other party, and mutual coupling will result in a decrease in the frequency difference between the two arms, resulting in an increase in detection difficulty and a decrease in sensitivity. Therefore, the length of the common optical fiber 021 should not be too long to reduce the two lasers. Coupling to avoid latch-up phenomenon similar to laser gyro.
  • the embodiment of the invention can realize the interference of the co-directional or reverse laser, and the application is relatively flexible.
  • an isolator can be disposed on the common optical fiber 021, or each of the detecting optical fiber 041 and the reference optical fiber 031 can be set. The same isolators.
  • reverse laser interference it is also possible to provide reversed isolators 14 in each of the reference fiber 031 and the detecting fiber 041 to isolate laser light in an unnecessary direction in each segment.
  • the use of the isolator 14 also prevents the effect of the backscattered light on the opposite laser in the same fiber on the desired laser, further improving the accuracy of the detection.
  • the gain medium 05 may be connected to the common optical fiber 021 in the form of a doped optical fiber, or may be connected to the common optical fiber 021 in the form of a separate gain device.
  • the wavelength division multiplexer 15 and the pump source 01 may be provided one by one, and two may be provided.
  • the two wavelength division multiplexers 15 are respectively disposed between the gain medium 05 and the first polarization coupler and the gain medium 05 and the Between the two polarization couplers, each of the wavelength division multiplexers 15 is connected to a pump source 01, and this structure can increase the laser power.
  • the first laser cavity and the second laser cavity have an initial optical path difference.
  • the delay unit 16 may be disposed on the reference fiber 031, and specifically may be a fiber delay device to enable the light.
  • the path difference is as small as possible for the photodetector to detect.
  • an adjustable attenuation unit may be disposed on both the reference fiber 031 and the detection fiber 041. 17, it is also possible to provide an adjustable attenuation unit 17 only on the reference fiber 031 or the detection fiber 041. When the intensity of one of the arms is low, the intensity difference of the two arms is reduced by adjusting the adjustable attenuation unit 17. .
  • a single frequency acquisition unit 18 may be disposed on the common optical fiber 021, or a single frequency acquisition unit 18 may be disposed on each of the reference optical fiber 031 and the detection optical fiber 041 to make the first laser cavity and the second excitation
  • the optical resonators only transmit laser light of one frequency, thereby improving the contrast of the interference fringes.
  • the single frequency acquisition unit 18 may be a narrowband filter, or may be a unit composed of two collimating lenses and an F-P interferometer therebetween, and the two collimating lenses are free spaces between them.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • the first laser cavity and the second laser cavity of this embodiment are annular cavity structures.
  • the common section 02 includes a dichroic mirror 022, and a plurality of mirrors 023 and an output mirror 091 as an output unit 09.
  • the dichroic mirror 022 is located in the output direction of the pump source 01, and the dichroic mirror 022, the mirror 023, and the output mirror 091 constitute An annular optical path is provided between the two mirrors 023 and a first polarization splitting unit 07 and a second polarization splitting unit 08.
  • the first polarization splitting unit 07 and the second polarization splitting unit 08 may employ a polarization splitting element that splits the incident light into S light and P light having different polarization directions, wherein the S light is reflected and reflected as the detection light through the mirror 023.
  • the P light is directly transmitted as the reference light to the second polarization splitting unit 08.
  • the sensing element 06 is placed on the path of the S light.
  • a first half-reverse half lens 19 and a prism 20 are respectively provided, which can reflect incident light to the first half-reverse half lens 19, at the output mirror 091 and
  • a polarization rotation unit 12 is provided between the first half reverse half lens 19, or between the output mirror 091 and the prism 20, or between the prism 20 and the first half reverse half lens 19.
  • the photodetector is disposed in the exit direction of the first half-reverse half lens 19. This output mode is suitable for interference detection of reverse S and P light.
  • the working principle of the embodiment of the present invention is that the pump light from the pump source 01 enters the common section 02 through the dichroic mirror 022, and the excitation gain medium 05 generates excitation light to both sides, and the clockwise excitation light passes through the first polarization beam splitting unit 07.
  • Divided into S light and P light P light enters reference segment 03, S light enters detection segment 04, and S light and P light merge at the second polarization splitting unit 08 into a beam of light entering the common segment 02 to continue transmission.
  • the counterclockwise excitation light is divided into S light and P light by the second polarization splitting unit 08, the P light enters the reference segment 03, the S light enters the detection segment 04, and the S light and the P light merge at the first polarization splitting unit 07 into one.
  • the beam enters the common segment 02 and continues to transmit.
  • the sensor is two ring lasers that are transmitted in reverse.
  • the output mirror 091 outputs clockwise and counterclockwise lasers respectively, in which the S light of one laser beam interferes with the P light of the other laser beam, Taking FIG. 3 as an example, the clockwise S light passes through the output mirror 091 and is reflected by the prism 20 to the first half reverse half lens 19, and the counterclockwise P light is directly transmitted to the first half reverse half lens 19 via the output mirror 091. After the S light passes through the polarization state rotation unit 12, it becomes P light, and the two P lights are combined into one beam at the first half reverse half lens 19 and then detected by the photodetector 11.
  • the output direction of the output mirror 091 may be provided with a third polarization splitting unit 21, and the S-light reflected light path of the third polarization splitting unit 21 is provided with a plurality of mirrors 22 and a polarization rotation unit. 12.
  • a second half-reverse half lens 23 is provided on the transmitted light path of the P light, and the photodetector 11 is disposed in the outgoing direction of the second half-half half lens 23.
  • the polarization state rotation unit 12 can also be disposed on the transmitted light path of the P light. This output method is suitable for interference detection of S and P light in the same direction.
  • the reverse isolator 14 when the S-light and the P-light in the opposite direction are used for detection, the reverse isolator 14 can be disposed in the reference section 03 and the detection section 04, and the isolator 14 can also prevent the same in the same optical path.
  • the backscattered light of the opposing laser is incorporated into the desired laser to ensure detection accuracy and accuracy.
  • the same-direction isolator 14 may be disposed in the reference section 03 and the detection section 04, or the isolator 14 may be disposed in the common section 02.
  • an adjustable attenuation unit 17 may be disposed in each of the reference segment 03 and the detection segment 04, or only one adjustable attenuation unit 17 may be disposed in the reference segment 03 or the detection segment 04;
  • the delay unit 16 is provided;
  • a single frequency acquisition unit 18 may be provided in each of the reference segment 03 and the detection segment 04, or a single frequency acquisition unit 18 may be provided in the common segment 02.
  • the functions of the above-mentioned devices are the same as those in the first embodiment, and will not be described in detail in this embodiment.
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • the first laser cavity and the second laser cavity of this embodiment are annular cavity structures.
  • the common segment 02 of the sensor is transmitted in free space, and the detecting segment 04 and the reference segment 03 are transmitted by polarization-maintaining fibers.
  • the common section 02 is connected by the first polarization splitting unit 07 and the second polarization splitting unit 08 and the reference section 03 and the detection section 04.
  • the common section 02 includes a dichroic mirror 022 and a plurality of mirrors 023, and an output mirror 091 is provided in the common section 02, and the output direction of the output mirror 091 can be third.
  • the polarization beam splitting unit 21 is provided with a plurality of mirrors 22 and a polarization state rotating unit 12 in the S light reflection path of the third polarization beam splitting unit 21, and a half mirror half 23 is provided on the transmitted light path of the P light.
  • the device 11 is disposed in the outgoing direction of the half mirror half lens 23. These devices may be arranged in the manner described in the second embodiment above.
  • the reference segment 03 and the detecting segment 04 respectively include a reference fiber 031 and a detecting fiber 041, and corresponding devices are disposed on the reference fiber 031 and the detecting fiber 041 as described in the first embodiment, which will not be described in detail in this embodiment.
  • the first polarization splitting unit 07 and the second polarization splitting unit 08 are connected to the collimating focusing mirror group 024 through a small length of optical fiber for realizing optical path transmission between the free space and the polarization maintaining fiber.
  • an output coupler is disposed on each of the reference fiber 031 and the detecting fiber 041, and one of the output couplers is connected to the polarization rotation unit 12 for making the polarization states of the output of the two output couplers uniform.
  • the output unit 09 can also be set in the common section 02, as described in the second embodiment, and the description is not repeated here.
  • the adjustable attenuation unit 17 may be disposed in the detection section 04 and the reference section 03, the delay unit 16 is set in the reference section 03, the single frequency acquisition unit 18 is set in the common section 02, or the detection section 04 is in the detection section 04.
  • a single frequency acquisition unit 18 is provided for each of the reference segments 03. The functions of the devices are the same as those of the first and second embodiments, and are not described herein again.
  • Embodiment 4 is a diagrammatic representation of Embodiment 4:
  • the first laser cavity and the second laser cavity of this embodiment have a straight cavity structure.
  • the common section 02 includes a first common section and a second common section
  • the gain medium 05 is disposed in the first common section 02, the reference section 03 and the detection section 04.
  • the two ends are connected in parallel between the first common segment and the second common segment through the first polarization splitting unit 07 and the second polarization splitting unit 08, respectively, and the common segment 02, the reference segment 03 and the detection segment 04 are transmitted by polarization-maintaining fibers.
  • Each includes a first common optical fiber 0211, a second common optical fiber 0212, a reference optical fiber 031, and a detection optical fiber 041.
  • the sensing element 06 capable of causing the optical path difference is disposed on the detecting optical fiber 041, and the first polarizing beam splitting unit 07 and the second polarizing beam splitting unit 08 may employ a polarization coupler.
  • the first common optical fiber 0211 is provided with a first reflection sheet at the end Element 025, which may be plated with a high reflective film or a high mirror, may also be provided with a collimating mirror on the inner side of the high mirror, or an FBG device as the first reflecting unit.
  • the gain medium 05 is disposed on the first common optical fiber 0211, and the first common optical fiber 0211 may further be provided with a wavelength division multiplexer 15, and the pump light from the pump source 01 passes through the wavelength division multiplexer 15 to enter the first common optical fiber. 0211, used to pump gain medium 05.
  • the gain medium 05 may be connected in the first common optical fiber 0211 in the form of a gain doped fiber, or may be connected to the first common optical fiber 0211 in the form of a separate gain device.
  • an output coupler is respectively disposed on the reference optical fiber 031 and the detecting optical fiber 041 as an output unit 09, and a polarization rotation unit 12 is disposed on the outgoing optical path of one of the output couplers, and is subjected to polarization.
  • the light output from the state rotation unit 12 is the same as the polarization state of the light output through the other output coupler, and the two beams pass through the light combining unit 10 to enter the photodetector 11.
  • the end of the second common optical fiber 0212 is provided with a second reflection unit 026 having the same structure as the first reflection unit 025.
  • the output unit 09 may be disposed at the end of the second common optical fiber 0212.
  • an output mirror 091 is disposed at the end of the second common optical fiber 0212, and a third polarization splitting unit 21 is disposed on the outgoing optical path of the output mirror 091.
  • the third polarized light splitting unit 21 may employ a polarization splitter at the polarization.
  • a plurality of mirrors 023 are disposed on the reflected light path of the beam splitter, and a semi-reverse half lens 24 is disposed on the transmitted light path of the polarizing beam splitter.
  • the light output from the output mirror 091 is divided into S light and P light after passing through the polarization beam splitter.
  • the S light is reflected and passed through the series mirror 023, and is changed by the polarization state rotation unit 12 to be the same as the P light polarization state, and reaches the half mirror half 24, and the P light is directly transmitted through the polarization beam splitter to the half mirror half 24
  • the two polarized lights interfere with each other after the light is combined at the half mirror half 24, and are detected by the photodetector 11.
  • the sensor provided in this embodiment performs interference detection by the S-light and the P-light in the same direction, and the working principle is the same as that in the above embodiment, and details are not described herein again.
  • the adjustable attenuation unit 17 may be disposed on the detecting optical fiber 041 and the reference optical fiber 031, or the adjustable attenuation unit 17 may be disposed on one of the two; or the delay unit may be disposed on the reference optical fiber 031. 16; it is also possible to set the single frequency acquisition unit 18 on the common optical fiber 021, or to detect the optical fiber A single frequency acquisition unit 18 is provided for each of 041 and the reference optical fiber 031. The functions of the respective devices are the same as those in the above embodiments, and are not described herein again.
  • Embodiment 5 is a diagrammatic representation of Embodiment 5:
  • the first laser cavity and the second laser cavity of this embodiment have a straight cavity structure.
  • the first common segment 02, the second common segment 02, the detection segment 04, and the reference segment 03 are all transmitted in free space.
  • the first common segment 02 includes at least a dichroic mirror 022 and a first polarization splitting unit 07
  • the gain medium 05 is disposed between the dichroic mirror 022 and the first polarization splitting unit 07
  • the second common segment 02 may include an output mirror 091 and The second polarization splitting unit 08.
  • the first polarization splitting unit 07 and the second polarization splitting unit 08 may employ a polarization beam splitter.
  • the reference segment 03 corresponds to a transmitted optical path between the first polarization splitting unit 07 and the second polarization splitting unit 08
  • the detection section 04 corresponds to a reflected optical path between the first polarization splitting unit 07 and the second polarization splitting unit 08, and is capable of generating light.
  • the sensor element 06 of the step is disposed in the detection section 04.
  • the third polarization splitting unit 25 is disposed in one direction of the output mirror 091.
  • the S-light reflection optical path of the third polarization beam splitting unit 25 is provided with a plurality of mirrors 26 and a polarization state rotation unit 12, and a transflective lens 27 is disposed on the transmission light path of the P-light, and the photodetector 11 is disposed at the The direction in which the half mirror half 27 is emitted. It can be understood that the polarization state rotation unit 12 can also be disposed on the transmitted light path of the P light.
  • the output unit 09 can also be set in the detection section 04 and the reference section 03, which will not be described in detail in this embodiment.
  • the reference segment 03 may also correspond to a reflected optical path between the first polarization splitting unit 07 and the second polarization splitting unit 08
  • the detection segment 04 corresponds to a transmitted optical path between the first polarization splitting unit 07 and the second polarization splitting unit 08.
  • the adjustable attenuation unit 17 may be simultaneously set in the detection section 04 and the reference section 03, or the adjustable attenuation unit 17 may be set in the detection section 04 or the reference section 03, and the delay is set in the reference section 03.
  • the unit 16 is provided with a single frequency acquisition unit 18 in the first common segment 02 or the second common segment 02, or a single frequency acquisition unit 18 is provided in each of the detection segment 04 and the reference segment 03, and the functions of the devices are the same as in the above embodiment. The role is the same and will not be described here.
  • the first laser cavity and the second laser cavity of this embodiment have a straight cavity structure. As shown in Figure 8, this issue
  • the first common segment and the second common segment of the embodiment are in the form of free space and fiber combination, while the detection segment 04 and the reference segment 03 are still transmitted by polarization-maintaining fibers, which respectively include the reference fiber 031 and the detection fiber 041.
  • the first common segment 02 includes a dichroic mirror 022, a collimating focusing mirror group 024, and a first polarization splitting unit 07.
  • the gain medium 05 is disposed on the optical path between the dichroic mirror 022 and the collimating focusing mirror group 024, and the pump source
  • the pump light emitted by 01 is excited by the dichroic mirror 022 to pump the excitation medium 05, and the excitation light passes through the collimating focusing mirror group 024 to enter a fiber segment, and the fiber segment is connected to the first polarization beam splitting unit 07, and the first polarization is passed.
  • the beam splitting unit 07 divides the excitation light into S light and P light, and enters the reference segment 03 and the detection segment 04, respectively.
  • the second common segment 02 includes a second polarization splitting unit 08, a collimating focusing mirror group 024, and a high mirror 025, which is also connected by a fiber segment and a second polarization beam splitting unit 08, in the reference segment 03.
  • the detection section 04 is provided with an output unit 09, specifically an output coupler, and the output coupler is connected by the light combining unit 10 and the photodetector 11.
  • a polarization rotation unit 12 is provided between one of the output couplers and the light combining unit 10.
  • an output mirror may be disposed at the end of the second common segment 02 as the output unit 09, and a third polarization splitting unit is disposed in the output direction of the output mirror, and the S-light reflection at the third polarization splitting unit is
  • the optical path is provided with a plurality of mirrors and a polarization state rotation unit, and a transflective lens is disposed on the transmission light path of the P light, and the photodetector is disposed in the exit direction of the semi-reverse lens. It can be understood that the polarization state rotation unit can also be disposed on the transmitted light path of the P light.
  • the above-mentioned adjustable attenuation unit 17, the delay unit 16, the single frequency acquisition unit 18, and the like may be disposed at corresponding positions, which are not described in this embodiment.
  • the S light and the P light are respectively used as the reference light and the detection light, and the S light may be used as the detection light and the P light may be used as the reference light.
  • the output unit 09 can be disposed in the reference segment 03 and the detection segment 04, or can be disposed in the common segment 02. Therefore, the present invention is not limited to the specific embodiments described above, and other embodiments are possible.
  • the present invention includes two straight cavity or annular cavity laser resonators, which may be in the form of an all-fiber or free space, or a free space and polarization-maintaining fiber.
  • the sensing element of the detecting section is subjected to the measured physical quantity to change the optical path quantity of the resonant cavity, thereby changing the laser frequency, and the magnitude of the measured physical quantity is obtained by detecting the frequency difference of the two lasers. Since the frequency difference is sensitive to the change of the optical path, the detection sensitivity and the detection accuracy are high, which is beyond the traditional detection method, and since there are common optical paths in the two straight cavities, the detection stability is good and the resistance is good. Strong interference, suitable for detection of small changes in various physical quantities.

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Abstract

一种基于激光器的传感器，属于传感技术领域，包括泵浦源（01）、公共段（02）以及参考段（03）和检测段（04），公共段（02）设有增益介质（05），检测段（04）设有能引起光程差的传感元件（06）；参考段（03）和检测段（04）通过第一、第二偏振分光单元（07,08）和公共段（02）连接；公共段（02）设有输出单元（09）或参考段（03）和检测段（04）各设有一输出单元（09），输出单元（09）通过合光单元（10）连接光电探测器（11）；在合光单元（10）和输出单元（09）之间还设有偏振态旋转单元（12）。该传感器由两路不同频率的激光发生外差干涉，通过检测频率差确定被测物理量的大小，由于激光频率对谐振腔的光程变化非常敏感，因此检测灵敏度和精度较高，并且该传感器的两个谐振腔存在共程的光路，抗干扰能力强，适合用于测量多种物理量的微小变化。

Description

一种基于激光器的传感器 技术领域
本发明属于光学传感技术领域，特别涉及一种基于激光器的传感器。
背景技术
现有技术中测量长度、温度、折射率、压力等物理量的微小变化时，通常采用激光相位型干涉法进行测量，基于马赫-曾德尔干涉仪的光学传感器是一种常见利用激光相位型干涉法进行测量的传感器，其原理是将激光器输出的激光分成两束，分别进入干涉仪的两臂中，两路光经过不同的传输路径后再汇合，形成干涉，由探测器检测两束光的相位差，进而确定被测的物理量。由于两个臂的光程量可以受到温度、压力等外在条件的影响，所以，马赫-曾德尔干涉仪可以实现应变、温度等物理量的测量，是许多传感器的重要物理基础。但这种传感器检测的是两束激光的相位差，其检测精度和灵敏度依然有限，需要提供一种新型的高精度、高灵敏度的光学传感器。
技术问题
本发明的目的在于提供一种基于激光器的传感器，旨在提高测量精度和灵敏度。
发明内容
本发明是这样实现的，一种基于激光器的传感器，包括泵浦源、公共段以及并列连接于所述公共段的两端之间的参考段和检测段，所述公共段设有增益介质，所述检测段设有能引起光程差的传感元件；
所述参考段和检测段的一端通过第一偏振分光单元与所述公共段连接，另 一端通过第二偏振分光单元与所述公共段连接；所述公共段和参考段构成传输第一线偏振光的第一激光谐振腔，所述公共段和检测段构成传输第二线偏振光的第二激光谐振腔；
所述公共段设有一输出单元或者所述参考段和检测段各设有一输出单元，所述输出单元通过合光单元连接光电探测器，激光从所述输出单元输出，经过合光后传输至所述光电探测器；在所述合光单元和输出单元之间还设有用于将第一线偏振光和第二线偏振光的偏振态变为一致的偏振态旋转单元。
有益效果
本发明提供的传感器包括偏振态不同的两个激光谐振腔，这两个激光谐振腔共用包含同一个增益介质的公共段，并且在检测段设置能引起光程差的传感元件，通过传感元件感应被测物理量，导致检测段传输激光频率发生变化，使两路激光产生频率差，由这两路不同频率的激光发生外差干涉，通过检测频率差确定被测物理量的大小，而由于激光振荡的频率对谐振腔的光程变化非常敏感，因此该传感器的检测灵敏度和精度远高于传统的基于相位差的传感器，并且该传感器的两个谐振腔存在共程的光路，外界环境导致公共段的变化所引起这两个激光器的频率变化基本一致，因此检测频率差值可以抵消这变化，因此该传感器抗干扰能力强，适合用于测量多种物理量的微小变化。
附图说明
图1是本发明第一实施例提供的基于激光器的传感器的结构示意图；
图2是本发明第一实施例提供的基于激光器的传感器的另一结构示意图；
图3是本发明第二实施例提供的基于激光器的传感器的结构示意图；
图4是本发明第三实施例提供的基于激光器的传感器的结构示意图；
图5是本发明第四实施例提供的基于激光器的传感器的结构示意图；
图6是本发明第四实施例提供的基于激光器的传感器的另一结构示意图；
图7是本发明第五实施例提供的基于激光器的传感器的结构示意图；
图8是本发明第六实施例提供的基于激光器的传感器的结构示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
以下结合具体实施例对本发明的具体实现进行详细描述：
请参考图1和图2，本发明实施例提供一种基于激光器的传感器，包括泵浦源01、公共段02以及并列连接于公共段02的两端之间的参考段03和检测段04，公共段02设有增益介质05，检测段04设有能引起光程差的传感元件06。参考段03和检测段04的一端通过第一偏振分光单元07与公共段02连接，另一端通过第二偏振分光单元08与公共段02连接；第一偏振分光单元07和第二偏振分光单元08可以将入射光分为偏振方向不同的第一线偏振光和第二线偏振光，公共段02和参考段03构成传输第一线偏振光的第一激光谐振腔，公共段02和检测段04构成传输第二线偏振光的第二激光谐振腔；公共段02设有一输出单元09，或者参考段03和检测段04各设有一输出单元09，输出单元09通过合光单元10连接光电探测器11，在合光单元10和输出单元09之间还设有用于将第一线偏振光和第二线偏振光的偏振态变为一致的偏振态旋转单元12。激光从输出单元09输出，其中一种线偏振光经过偏振态旋转单元12后其偏振方向与另一线偏振光相同，两束偏振态相同的线偏振光经过合光单元10合光后传输至光电探测器11，进行干涉检测。
为了便于说明，本发明实施例将第一线偏振光记为P光，将第二线偏振光记为S光，即以P光作为参考光，以S光作为检测光。
该传感器的工作原理为：泵浦源01发出泵浦光进入公共段02，并激发增益介质05向两侧产生激发光，激发光经过第一偏振分光单元07分为S光和P 光，并且使P光进入参考段03，S光进入检测段04，被测物理量作用于检测段04的传感元件06上，使第二谐振腔的腔长发生变化，从而改天了S光的频率，由于第一谐振腔腔长没有改变，因此而P光频率没有变化，这样，第一激光谐振腔和第二激光谐振腔中的激光产生与该外界通过传感元件06引起的光程变化相关的频率差，两个谐振腔中不同频率的激光经输出单元09输出并进行外差干涉，然后由光电探测器光电探测器检测干涉图样，进而获得两路激光的频率差，根据该频率差可以确定被测物理量的大小。具体的，在第一激光谐振腔中，激光频率为
Figure PCTCN2015072694-appb-000001
在第二激光谐振腔中，激光频率为
Figure PCTCN2015072694-appb-000002
其中C为光速，纵模数q为整数，L1和L2分别为第一、第二激光谐振腔的光程。由于传感元件06产生的光程变化导致两谐振腔中的光程差为ΔL＝L1-L2。则频率差
Figure PCTCN2015072694-appb-000003
公式中，L是第一、第二激光谐振腔光程的平均值，ν是第一激光谐振腔、第二激光谐振腔的频率的平均值。λ为激光器的波长。由于该公式中，分子中的光速C是一个很大的值，而分母中的λ是一个很小的量。因此当光程L发生微小变化时，由于分子是一个很大值，而分母是一个很小的值，因此频率差Δν也会发生较大变化，因此，该传感器具有明显高于传统传感器(马赫-曾德尔干涉仪等)的灵敏度和检测精度，并且该传感器的两个谐振腔存在共程的光路，外界环境导致公共段02的变化所引起这两个激光器的频率变化基本一致，因此检测频率差值可以抵消这变化，因此该传感器受外接环境影响小，抗干扰能力强，适合用于测量多种物理量的微小变化。
本发明实施例中的第一激光谐振腔和第二激光谐振腔既可以是直腔结构，又可以是环形腔结构。以下结合具体的实施例对本发明进行详细说明：
实施例一：
本实施例的第一激光谐振腔和第二激光谐振腔为环形腔结构。该传感器的公共段02、参考段03和检测段04均采用保偏光纤传输，公共段02包括公共光纤021，参考段03包括参考光纤031，检测段04包括检测光纤041，能引起 光程差的传感元件06设置于检测光纤041上。公共光纤021的两端分别通过第一偏振分光单元07和第二偏振分光单元08(本实施例采用偏振耦合器作为偏振分光单元)连接检测光纤041和参考光纤031。在公共光纤021上设有波分复用器15，在检测光纤041和参考光纤031上分别设有一输出单元09，具体可以是输出耦合器，两输出耦合器连接一合光单元10，合光单元10连接光电探测器11。在一个输出耦合器和合光单元10之间设有偏振态旋转单元12。
该传感器的工作原理为：泵浦光经波分复用器15进入公共光纤021，激发增益介质05向两侧发出激发光，其中，逆时针的激发光经过第一偏振分光单元07后分为S光和P光，P光进入参考光纤031，S光进入检测光纤041，顺时针的激发光经过第二偏振分光单元08后分为S光和P光，其中P光进入参考光纤031，S光进入检测光纤041，这样，在第一激光谐振腔和第二激光谐振腔中均传输方向相反的两束光，在参考光纤031中传输方向相反的两束S光，在检测光纤041中传输方向相反的两束P光。这种结构的传感器可以通过相反方向S光和P光的干涉进行检测，也可以通过相同方向S光和P光的干涉进行检测，主要根据输出方式确定。
作为一种输出方式，可以采用两个输出耦合器作为输出单元，使一个输出耦合器输出顺时针的S光(或P光)，使另一个输出耦合器输出逆时针的P光(或S光)，此时是由两束反向传输的激光发生干涉。
在其他实施例中，也可以将输出单元09设置于公共光纤021上，具体可以是一种具有四个端口的耦合器，也可以是三端口的耦合器，如图2所示，在公共光纤021上设置一输出耦合器，该耦合器具有一个输出端，该输出端连接第三偏振分光单元13，将光束分为S光和P光，在S光或P光的光路上设置偏振态旋转单元12，将两束光的偏振态变为一致，然后通过合光单元10输入至光电探测器11。
在本发明实施例中，公共光纤021作为两谐振腔的公共段02，由于两个谐振腔中的激光在此公共段02会产生一定的相互耦合，例如采用反向激光进行干 涉，顺时针谐振腔和逆时针谐振腔的激光都经过该段传输，在传输的过程中，不可避免发生后向散射，而后向散射的激光必然参与到另一路激光当中，这样两臂激光的后向散射光参与对方光路传输，相互耦合将导致两臂激光频率差减小，导致检测难度加大，灵敏性降低，因此，该公共光纤021的长度不宜过长，以减小两路激光的耦合，避免发生类似激光陀螺的闭锁现象。
本发明实施例可以实现同向或反向激光的干涉，应用比较灵活，在采用同向光干涉的情况下，可以在公共光纤021设置一个隔离器，或在检测光纤041和参考光纤031各设置同向的隔离器。当采用反向激光干涉时，也可以在参考光纤031和检测光纤041各设置反向的隔离器14，将各段内不需要的方向的激光隔离。采用隔离器14还可以防止同光纤中的对向激光产生后向散射光对所需激光的影响，进一步提高检测的准确性。
在本发明实施例中，增益介质05可以以掺杂光纤的形式连接于公共光纤021，也可以以单独的增益器件的形式连接于公共光纤021上。波分复用器15和泵浦源01可以各设置一个，还可以设置两个，两个波分复用器15分别设置在增益介质05和第一偏振耦合器之间以及增益介质05和第二偏振耦合器之间，每个波分复用器15各连接一泵浦源01，这种结构可以提高激光功率。
进一步的，第一激光谐振腔和第二激光谐振腔存在初始光程差，为了补偿初始光程差，可以在参考光纤031上设置延时单元16，具体可以是光纤延时器，使该光程差尽量小，以便光电探测器检测。
进一步的，激光在谐振腔中传输必然有损耗，为了避免第一激光谐振腔和第二激光谐振腔的光能量相差过大，可以在参考光纤031和检测光纤041上均设置一可调衰减单元17，也可以只在参考光纤031或检测光纤041上设置一个可调衰减单元17，当其中一臂光强较低时，通过调整可调衰减单元17，减小两臂激光的光强差值。
进一步的，还可以在公共光纤021设置一单频获取单元18，或者在参考光纤031和检测光纤041各设置一单频获取单元18，使第一激光谐振腔和第二激 光谐振腔均只传输一种频率的激光，进而改善干涉条纹的对比度。进一步的，该单频获取单元18可以是窄带滤波器，也可以是由两个准直透镜和二者之间的F-P干涉仪构成的单元，两个准直透镜之间为自由空间。
实施例二：
本实施例的第一激光谐振腔和第二激光谐振腔为环形腔结构。参考图3，该传感器的公共段02、检测段04和参考段03均采用自由空间传输。公共段02含有一双色镜022，以及若干个反射镜023和作为输出单元09的输出镜091，该双色镜022位于泵浦源01的输出方向，双色镜022、反射镜023及输出镜091构成一环形光路，在其中的两个反射镜023之间设有第一偏振分光单元07和第二偏振分光单元08。该第一偏振分光单元07和第二偏振分光单元08可以采用偏振分光元件，使入射光分为偏振方向不同的S光和P光，其中，S光被反射，作为检测光通过反射镜023反射至第二偏振分光单元08，P光作为参考光直接透射至第二偏振分光单元08。传感元件06设置于S光的路径上。在输出镜091的两个不同的输出方向上，分别设有第一半反半透镜19和一棱镜20，该棱镜20可以将入射光反射至第一半反半透镜19，在输出镜091和第一半反半透镜19之间，或者在输出镜091和棱镜20之间，或者在棱镜20和第一半反半透镜19之间设有偏振态旋转单元12。光电探测器设置于第一半反半透镜19的出射方向。这种输出方式适合反向的S光和P光进行干涉检测。
本发明实施例的工作原理为：泵浦源01发出的泵浦光经过双色镜022进入公共段02，激发增益介质05向两侧产生激发光，顺时针的激发光经过第一偏振分光单元07分为S光和P光，P光进入参考段03，S光进入检测段04，S光与P光在第二偏振分光单元08处汇合为一束光进入公共段02继续传输。逆时针的激发光经过第二偏振分光单元08分为S光和P光，P光进入参考段03，S光进入检测段04，S光与P光在第一偏振分光单元07处汇合为一束光进入公共段02继续传输。该传感器为两个反向传输的环形激光器。输出镜091将顺时针和逆时针的激光分别输出，其中一束激光的S光和另一束激光的P光干涉， 以图3所示为例，顺时针的S光经过输出镜091后由棱镜20反射至第一半反半透镜19，逆时针的P光经输出镜091直接传输至第一半反半透镜19，S光经过偏振态旋转单元12后变为P光，两束P光在第一半反半透镜19处合为一束后由光电探测器11探测。
在其他实施例中，例如图4，输出镜091的输出方向可以设置第三偏振分光单元21，在该第三偏振分光单元21的S光反射光路设有若干个反射镜22以及偏振态旋转单元12，在其P光的透射光路上设有第二半反半透镜23，光电探测器11设置于该第二半反半透镜23的出射方向。可以理解，偏振态旋转单元12还可以设置在P光的透射光路上。这种输出方式适用于同方向的S光和P光的干涉检测。
同实施例一相同的是，当采用反方向的S光和P光进行检测时，可以在参考段03和检测段04设置反向隔离器14，该隔离器14同样可以防止同光路中不需要的对向激光的后向散射光参与所需激光中，进而保证检测准确性和精度。当采用同方向的S光和P光进行检测时，可以在参考段03和检测段04设置同向隔离器14，或在公共段02设置隔离器14。
在本发明实施例中，也可以在参考段03和检测段04各设置一个可调衰减单元17，或者只在参考段03或检测段04设置一个可调衰减单元17；还可以在参考段03设置延时单元16；还可以在参考段03和检测段04各设置一个单频获取单元18，或在公共段02设置一单频获取单元18。上述器件的作用与其在实施例一中的作用相同，本实施例不再赘述。
实施例三：
本实施例的第一激光谐振腔和第二激光谐振腔为环形腔结构。如图4，本发明实施例中，该传感器的公共段02采用自由空间传输，检测段04和参考段03均采用保偏光纤传输。公共段02通过第一偏振分光单元07和第二偏振分光单元08和参考段03及检测段04连接。公共段02包括双色镜022及若干个反射镜023，并且在公共段02设有输出镜091，输出镜091的输出方向可以第三 偏振分光单元21，在该第三偏振分光单元21的S光反射光路设有若干个反射镜22以及偏振态旋转单元12，在其P光的透射光路上设有半反半透镜23，光电探测器11设置于该半反半透镜23的出射方向。这些器件按照上述实施例二所述的方式设置即可。参考段03和检测段04分别包括参考光纤031和检测光纤041，并如实施例一所述在参考光纤031和检测光纤041上设置相应器件，本实施例不再赘述。另外，第一偏振分光单元07和第二偏振分光单元08通过一小段光纤连接准直聚焦镜组024，用于实现自由空间和保偏光纤之间的光路传输。
本实施例在参考光纤031和检测光纤041上各设置一输出耦合器，其中一个输出耦合器连接偏振态旋转单元12，用于将两个输出耦合器输出光的偏振态变为一致。
当然，本实施例也可以在公共段02设置输出单元09，如实施例二所述，此处不再重复说明。
在本发明实施例中，还可以在检测段04、参考段03设置可调衰减单元17，在参考段03设置延时单元16，在公共段02设置单频获取单元18，或者在检测段04和参考段03各设一个单频获取单元18，各器件的作用同其在实施例一和二中的作用相同，此处不再赘述。
实施例四：
本实施例的第一激光谐振腔和第二激光谐振腔为直腔结构。如图5和图6，包括泵浦源01、公共段02，该公共段02包括第一公共段和第二公共段，增益介质05设置于第一公共段02，参考段03和检测段04的两端分别通过第一偏振分光单元07和第二偏振分光单元08并列连接于第一公共段和第二公共段之间，公共段02、参考段03和检测段04均采用保偏光纤传输，分别含有第一公共光纤0211、第二公共光纤0212、参考光纤031和检测光纤041。能引起光程差的传感元件06设置于检测光纤041上，第一偏振分光单元07和第二偏振分光单元08可以采用偏振耦合器。第一公共光纤0211的末端设有第一反射单 元025，具体可以镀有高反膜或设置高反镜，还可以在高反镜的内侧设置准直镜，也可以采用FBG器件作为第一反射单元。增益介质05设置于第一公共光纤0211上，第一公共光纤0211上还可以设有一波分复用器15，泵浦源01发出的泵浦光经过波分复用器15进入第一公共光纤0211，用于泵浦增益介质05。增益介质05可以以增益掺杂光纤的形式连接在第一公共光纤0211内，也可以以单独的增益器件的形式连接于第一公共光纤0211上。
作为一种输出方式，如图5，在参考光纤031和检测光纤041上分别设置一个输出耦合器，作为输出单元09，在其中一个输出耦合器的出射光路上设置偏振态旋转单元12，经过偏振态旋转单元12输出的光与经过另一输出耦合器输出的光的偏振态相同，两束光经过合光单元10进入光电探测器11。此时，第二公共光纤0212的末端设有第二反射单元026，其结构与第一反射单元025相同。
作为另一种输出方式，如图6，该输出单元09可以设置于第二公共光纤0212的末端。具体的，在第二公共光纤0212的末端设置一输出镜091，在输出镜091的出射光路上设有第三偏振分光单元21，该第三偏振分光单元21可以采用偏振分光器，在该偏振分光器的反射光路上设有若干个反射镜023，在偏振分光器的透射光路上设有一个半反半透镜24，输出镜091输出的光经过偏振分光器后分为S光和P光，S光被反射后经过系列反射镜023，被偏振态旋转单元12改变偏振态后与P光偏振态相同，并到达半反半透镜24，P光直接经过偏振分光器透射至半反半透镜24，两束偏振光在半反半透镜24处合光后发生干涉，由光电探测器11进行探测。
本实施例提供的传感器是通过同向的S光和P光进行干涉检测，其工作原理同上述实施例相同，此处不再赘述。
在本发明实施例中，还可以在检测光纤041和参考光纤031上设置可调衰减单元17，或在二者之一上设置可调衰减单元17；还可以在参考光纤031上设置延时单元16；还可以在公共光纤021设置单频获取单元18，或者在检测光纤 041和参考光纤031各设一个单频获取单元18。各器件的作用同其在上述实施例中的作用相同，此处不再赘述。
实施例五：
本实施例的第一激光谐振腔和第二激光谐振腔为直腔结构。如图7，第一公共段02、第二公共段02、检测段04和参考段03均采用自由空间传输。具体的，第一公共段02至少包括双色镜022和第一偏振分光单元07，增益介质05设置于双色镜022和第一偏振分光单元07之间，第二公共段02可以包括输出镜091和第二偏振分光单元08。第一偏振分光单元07和第二偏振分光单元08可以采用偏振分光器。参考段03对应于第一偏振分光单元07和第二偏振分光单元08之间的透射光路，检测段04对应第一偏振分光单元07和第二偏振分光单元08之间的反射光路，能够产生光程差的传感元件06设置于检测段04。在输出镜091的一个方向设置第三偏振分光单元25。在该第三偏振分光单元25的S光反射光路设有若干个反射镜26以及偏振态旋转单元12，在其P光的透射光路上设有半反半透镜27，光电探测器11设置于该半反半透镜27的出射方向。可以理解，偏振态旋转单元12还可以设置在P光的透射光路上。
当然，也可以在检测段04和参考段03设置输出单元09，本实施例不再赘述。另外，参考段03也可以对应第一偏振分光单元07和第二偏振分光单元08之间的反射光路，检测段04对应第一偏振分光单元07和第二偏振分光单元08之间的透射光路。
如以上实施例所述，本实施例还可以在检测段04和参考段03同时设置可调衰减单元17，或者检测段04或参考段03设置可调衰减单元17，在参考段03设置延时单元16，在第一公共段02或者第二公共段02设置单频获取单元18，或者在检测段04和参考段03各设一个单频获取单元18，各器件的作用同其在以上实施例中的作用相同，此处不再赘述。
实施例六：
本实施例的第一激光谐振腔和第二激光谐振腔为直腔结构。如图8，本发 明实施例的第一公共段和第二公共段采用自由空间和光纤组合的形式，而检测段04和参考段03依然采用保偏光纤传输，分别包含参考光纤031和检测光纤041。其中，第一公共段02包括双色镜022、准直聚焦镜组024和第一偏振分光单元07，增益介质05设置于双色镜022和准直聚焦镜组024之间的光路上，泵浦源01发出的泵浦光经过双色镜022泵浦激发增益介质05发出激发光，激发光经过准直聚焦镜组024进入一光纤段，该光纤段连接第一偏振分光单元07，通过该第一偏振分光单元07将激发光分为S光和P光，分别进入参考段03和检测段04。第二公共段02包括第二偏振分光单元08、准直聚焦镜组024和高反镜025，该准直聚焦镜组024同样通过一光纤段和第二偏振分光单元08连接，在参考段03和检测段04各设有一输出单元09，具体可以是输出耦合器，输出耦合器通过合光单元10和光电探测器11连接。在其中一个输出耦合器和合光单元10之间设有偏振态旋转单元12。
在其他实施例中，还可以在第二公共段02的末端设置输出镜，作为输出单元09，并在输出镜的输出方向设置第三偏振分光单元，在该第三偏振分光单元的S光反射光路设有若干个反射镜以及偏振态旋转单元，在其P光的透射光路上设有半反半透镜，光电探测器设置于该半反半透镜的出射方向。可以理解，偏振态旋转单元还可以设置在P光的透射光路上。
在本实施例中，还可以在相应位置设置上述的可调衰减单元17，延时单元16，单频获取单元18等，本实施例不再赘述。
在上述各实施例中，S光和P光分别作为参考光和检测光仅是一种实施例，也可以将S光作为检测光，将P光作为参考光。对于输出方式，无论采用保偏光纤或是自由空间传输，输出单元09既可以设置于参考段03和检测段04，也可以设置于公共段02。因此，本发明除上述具体的实施例外，还有其他可实施例的方式，本申请不进行一一说明。
综上所述，本发明包括两个直腔或环形腔激光谐振腔，这两个激光谐振腔可以采用全光纤形式，也可以为自由空间的形式，或者为自由空间和保偏光纤 的组合形式，检测段的传感元件受到被测物理量的作用后使谐振腔的光程量发生改变，进而改变激光频率，通过检测两路激光的频率差获得被测物理量的大小。由于频率差对光程的变化较为敏感，因此其检测灵敏性和检测精度较高，是传统检测方法所不能及的，且由于两个直腔中存在共程光路，因此检测稳定性好，抗干扰力强，适合用于多种物理量微小变化的检测。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (13)

  1. 一种基于激光器的传感器，其特征在于，包括泵浦源、公共段以及并列连接于所述公共段的两端之间的参考段和检测段，所述公共段设有增益介质，所述检测段设有能引起光程差的传感元件；
    所述参考段和检测段的一端通过第一偏振分光单元与所述公共段连接，另一端通过第二偏振分光单元与所述公共段连接；所述公共段和参考段构成传输第一线偏振光的第一激光谐振腔，所述公共段和检测段构成传输第二线偏振光的第二激光谐振腔；
    所述公共段设有一输出单元或者所述参考段和检测段各设有一输出单元，所述输出单元通过合光单元连接光电探测器，激光从所述输出单元输出，经过合光后传输至所述光电探测器；在所述合光单元和输出单元之间还设有用于将第一线偏振光和第二线偏振光的偏振态变为一致的偏振态旋转单元。
  2. 如权利要求1所述的传感器，其特征在于，所述公共段02包括第一公共段和第二公共段，所述参考段和检测段连接于所述第一公共段和第二公共段之间，所述第一公共段、第二公共段和参考段构成直腔结构的第一激光谐振腔，所述第一公共段、第二公共段和检测段构成直腔结构的第二激光谐振腔。
  3. 如权利要求1所述的传感器，其特征在于，所述公共段和参考段构成一环形的第一激光谐振腔，所述公共段和参考段构成一环形的第二激光谐振腔。
  4. 如权利要求1所述的传感器，其特征在于，所述公共段、参考段和检测段均采用保偏光纤传输。
  5. 如权利要求4所述的传感器，其特征在于，所述公共段设有波分复用器，所述泵浦源发出的泵浦光经过所述波分复用器进入所述公共段，用于泵浦增益介质。
  6. 如权利要求1所述的传感器，其特征在于，所述公共段、参考段和检测段均采用自由空间传输，或者所述公共段采用自由空间和光纤组合的形式传输，所述参考段和检测段采用保偏光纤传输。
  7. 如权利要求6所述的传感器，其特征在于，所述公共段包括设置于所述泵浦源的输出方向的双色镜，以及与所述双色镜形成自由空间光路的若干个反射镜。
  8. 如权利要求1至7任一项所述的传感器，其特征在于，所述输出单元设置于所述公共段，所述输出单元的输出方向设有第三偏振分光单元，用于将来自输出单元的光分为偏振方向不同的两路光，在其中一路光的路径中设有所述偏振态旋转单元。
  9. 如权利要求1、3至7任一项所述的传感器，其特征在于，所述输出单元设置于所述公共段，其具有两个输出方向，分别输出不同偏振态的线偏振光，在其中一个输出方向设有一半反半透镜，在另一输出方向设有一棱镜，并在其中一个输出方向设有所述偏振态旋转单元，所述棱镜将线偏振光反射至所述半反半透镜并与另一线偏振光共同输入所述合光单元。
  10. 如权利要求1至7任一项所述的传感器，其特征在于，所述参考段和检测段各设有一输出单元，在其中一个输出单元和合光单元之间设有所述偏振态旋转单元。
  11. 如权利要求1所述的传感器，其特征在于，在所述参考段上设有延时单元。
  12. 如权利要求1所述的传感器，其特征在于，在所述参考段和/或检测段设有可调衰减单元。
  13. 如权利要求1所述的传感器，其特征在于，所述公共段设有单频获取单元，或者所述参考段和检测段各设有一单频获取单元。
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