CN106153174B - Phase demodulator, optical fiber sound pressure demodulating system, demodulation method and manufacturing method - Google Patents
Phase demodulator, optical fiber sound pressure demodulating system, demodulation method and manufacturing method Download PDFInfo
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Abstract
The present invention is suitable for sound pressure measurement engineering device technique field, provide a kind of phase demodulator, optical fiber sound pressure demodulating system, demodulation method and manufacturing method, the phase demodulator, using the structure of Sagnac fiber optic loop, including wideband light source, photodetector connects the signal analysis module of photodetector, further includes: is separately connected the first fiber coupler of wideband light source and photodetector；The first fiber coupler is connected, adjusts the intensity of CW light, or adjust the variable optical attenuator of the intensity of CCW light；Connect the fiber delay line of the first fiber coupler；It is separately connected fiber delay line and variable optical attenuator, the second fiber coupler of the light of coupled film chip optical fibre sound pressure sensor reflection；The second fiber coupler is connected, the optical frequency shifter of stable pi/2 quadrature phase biasing is provided；Optical frequency shifter is connected, and passes through the optical fiber depolarizer of the external diaphragm-type optical-fiber sound pressure sensor of optical fiber.The present invention realizes the stable phase angle demodulation of diaphragm-type optical-fiber sound pressure sensor.
Description
Technical field
The invention belongs to sound pressure measurement engineering device technique field more particularly to phase demodulator, optical fiber sound pressure demodulating system, solutions
Tune method and manufacturing method.
Background technique
Existing acoustic pressure demodulating system mostly uses greatly structure is simple, detects accurate Fiber Optic Fabry-Perot Sensor to survey
Acoustic pressure is measured, the Fabry-Perot-type cavity being made of fiber end face and diaphragm end face is generally included, when ambient pressure acts on elastic membrane
When on piece, deformation occurs for diaphragm, so that the chamber for changing Fabry-Perot-type cavity is long, passes through reflection caused by detection change of cavity length
The variation of interference of light phase difference, can realize sound pressure measurement.
However, existing phase demodulator, increases the complexity and difficulty of sensor demodulating system, and it cannot be used for structure
The different sensor of parameter (chamber is long), reduces flexibility and applicability.The reason is that detected by above-mentioned principle,
It is required that the operation wavelength for detecting light needs to stablize on the orthogonal operating point of Fabry-Perot-type cavity in signal acquisition process, from
And obtain optimum linearity workspace and detectivity.However the orthogonal operating point of Fabry-Perot-type cavity is easy by extraneous ring
Border, such as the influence of temperature change, therefore, major part optical fibre Fabry-perot diaphragm type sound pressure sensor, needs feedback at present
Control system adjusts detection optical wavelength in real time, and to realize stable signal measurement, and it is inclined to adjust orthogonal operating point i.e. phase in real time
It sets, is a complicated dynamic regulation step, increases the complexity and difficulty of sensor demodulating system；Simultaneously as production
The limitation of craft precision, the chamber of Fabry-Perot-type cavity is long and its corresponding orthogonal operating point be difficult it is completely the same, therefore for not
Same sensor, needs to readjust the detection optical wavelength of demodulating system, makes working sensor in quadrature phase offset operation point
On, it is greatly lowered the flexibility and applicability of the demodulating system in this way.
Summary of the invention
The embodiment of the present invention is designed to provide a kind of phase demodulator, it is intended to solve existing phase demodulating system and exist
Problem as described above.
The embodiments of the present invention are implemented as follows, a kind of phase demodulator, using the structure of Sagnac fiber optic loop, external film
Chip optical fibre sound pressure sensor, including wideband light source, photodetector connect the photodetector, receive the photoelectricity and visit
Survey the signal analysis module of the electric signal of device output, the phase demodulator further include:
It is separately connected the wideband light source and the photodetector, the light that wideband light source described in beam splitting issues is up time
First fiber coupler of needle transmission CW light and counterclockwise transmission CCW light；
Connect first fiber coupler, adjust the intensity of the CW light, or adjust the CCW light intensity can
Tune optical attenuator；
Connect the fiber delay line of first fiber coupler；
It is separately connected the fiber delay line and the variable optical attenuator, the diaphragm-type optical-fiber acoustic pressure is coupled and passes
Second fiber coupler of the light of sensor reflection；
Second fiber coupler is connected, the optical frequency shifter of stable pi/2 quadrature phase biasing is provided；
The optical frequency shifter is connected, and passes through the optical fiber depolarizer of the external diaphragm-type optical-fiber sound pressure sensor of optical fiber.
The another object of the embodiment of the present invention is to provide a kind of optical fiber sound pressure demodulating system, including above-mentioned phase demodulating
Device, the optical fiber sound pressure demodulating system further include:
The phase demodulator is connected using optical fiber and based on the diaphragm-type optical-fiber sound pressure sensor of graphene diaphragm.
The another object of the embodiment of the present invention is to provide the demodulation method of optical fiber sound pressure demodulating system, the demodulation method
Include:
The diaphragm-type optical-fiber sound pressure sensor is linked into Sagnac fiber optic loop with reflective mode operation；
By the optical frequency shifter in the Sagnac fiber optic loop CW light and CCW light carry out asymmetric frequency shifting
It is dynamic, so as to generate stable phase difference between CW and CCW light；
By changing the shift frequency amount of the optical frequency shifter or the length of fiber delay line, make the phase difference be equal to 2m π+
Pi/2, wherein m is natural number；
The output optical signal for demodulating the Sagnac fiber optic loop, obtains acoustic pressure to be measured.
The another object of the embodiment of the present invention is to provide a kind of optical fiber sound pressure based on above-mentioned optical fiber sound pressure demodulating system
The manufacturing method of sensor, comprising the following steps:
Prepare graphite film；
The graphite film is fixed along supporter bore edges；
In the side of supporter, process air pressure balance hole；
At the center of supporter, optical fiber fixed hole is set；
Section is handled into the optical fiber for inclined-plane, through the optical fiber fixed hole close to the graphite film, adjusts the light
It is fine to be fixed at a distance from the graphite film, and to the optical fiber, the diaphragm-type optical-fiber sound pressure sensor can be obtained.
In embodiments of the present invention, connection second fiber coupler is provided, it is inclined to provide stable pi/2 quadrature phase
The optical frequency shifter set solves complexity height in existing phase demodulator, cannot be suitble to the sensor of Different structural parameters, flexibly
Property and applicability it is low equal the problem of.Stable pi/2 quadrature phase is provided to Sagnac optical fiber ring structure using optical frequency shifter to bias,
Influence of the outside noise to diaphragm-type optical-fiber sound pressure sensor operating point is reduced, to reduce answering for sensor demodulating system
Miscellaneous degree and difficulty.Without complicated Real-time Feedback regulation, always work in diaphragm-type optical-fiber sound pressure sensor most preferably
The linearity and maximum sensitivity state realize the stable phase angle demodulation of diaphragm-type optical-fiber sound pressure sensor, and structure is simple, surely
Ding Dugao, applicability is good, and can be used for other types of sensor.
Detailed description of the invention
Fig. 1 is the structural block diagram of phase demodulator 10 provided in an embodiment of the present invention；
Fig. 2 is the implementation flow chart of phase demodulator 10 provided in an embodiment of the present invention；
Fig. 3 is the preferable structural schematic diagram of phase demodulator 10 provided in an embodiment of the present invention；
Fig. 4 is the structural block diagram of optical fiber sound pressure demodulating system provided in an embodiment of the present invention；
Fig. 5 is the structural schematic diagram of optical fiber sound pressure demodulating system provided in an embodiment of the present invention；
Fig. 6 is the implementation flow chart of the demodulation method provided in an embodiment of the present invention based on optical fiber sound pressure demodulating system；
Fig. 7 is optical fiber sound pressure demodulating system provided in an embodiment of the present invention, and output signal power composes preferable sample figure；
Fig. 8 is optical fiber sound pressure demodulating system provided in an embodiment of the present invention, and output signal power changes with time preferably
Sample figure；
Fig. 9 is the structural schematic diagram of diaphragm-type optical-fiber sound pressure sensor 20 provided in an embodiment of the present invention；
Figure 10 is the manufacture stream of diaphragm type sound pressure sensor 20 in optical fiber sound pressure demodulating system provided in an embodiment of the present invention
Cheng Tu.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.
Embodiment one
Fig. 1 is the structural block diagram of phase demodulator 10 provided in an embodiment of the present invention, and details are as follows:
A kind of phase demodulator 10, using the structure of Sagnac fiber optic loop, external diaphragm-type optical-fiber sound pressure sensor 20, packet
Wideband light source 101 is included, photodetector 102 connects the photodetector 102, receives what the photodetector 102 exported
Electric signal and the signal analysis module demodulated, which is characterized in that the phase demodulator 10 further include:
It is separately connected the wideband light source 101 and the photodetector 102, wideband light source 101 described in beam splitting issues
Light be clockwise transmission CW light and counterclockwise transmission CCW light the first fiber coupler 103；
First fiber coupler 103 is connected, adjusts the intensity of the CW light, or adjust the intensity of the CCW light
Variable optical attenuator 104；
Connect the fiber delay line 105 of first fiber coupler 103；
It is separately connected the fiber delay line 105 and the variable optical attenuator 104, couples the diaphragm-type optical-fiber
Second fiber coupler 106 of the light that sound pressure sensor 20 reflects；
Second fiber coupler 106 is connected, the optical frequency shifter 107 of stable pi/2 quadrature phase biasing is provided；
The optical frequency shifter 107 is connected, and is depolarized by the optical fiber of the external diaphragm-type optical-fiber sound pressure sensor 20 of optical fiber
Device 108.
Wherein, the end face of optical fiber is that inclined cut is formed, and makes the reflectivity of the end face of the optical fiber far below normal vertical light
Fine end face, can be ignored, thus effective Fabry-Perot interference chamber can not be formed with graphite film 201；Optical fiber 204
Transmission incident light is only used for graphite film 201 and receives the light returned by film reflector；When there is acoustic pressure effect in the external world, graphite is thin
Deformation occurs and modulates the phase for returning to optical fiber light for film 201.By detecting the phase change, so that it may obtain sound pressure signal.
Wherein, it uses optical frequency shifter 107 to provide stable quadrature phase biasing for optical fiber Sagnac ring, can be effectively reduced
External environment changes disturbance to optical fibre sound pressure sensor, thus enable the sensor to long-term stable operation in optimum linear degree and
Sensitivity state.The quadrature phase biasing of the demodulating system is independent of sensor cavity length and its length of transmission fiber 109, pole
The applicability of system is improved greatly.
Further, in phase demodulator 10, first fiber coupler 103 and the second fiber coupler 106 are
The identical fiber coupler of splitting ratio.
Further, the fiber coupler is 3dB fiber coupler.
Further, in phase demodulator 10, the optical frequency shifter 107 is located at the fiber coupler and the light
Between fine depolarizer 108.
Further, in phase demodulator 10, the delay, τ that the fiber delay line 105 provides meets τ=1/2f,
Middle f is the centre frequency of sound pressure signal to be detected.
Further, in phase demodulator 10, the optical fiber depolarizer 108 uses length ratio for 1:2, and fast axle is at 45
Two sections of polarization maintaining optical fibre weldings at degree angle are formed；Alternatively,
Use length than being formed for 1:2, slow axis at two sections of polarization maintaining optical fibre weldings at 45 degree of angles.
Referring to figs. 2 and 3, Fig. 2 is the implementation flow chart of phase demodulator 10 provided in an embodiment of the present invention, is described in detail such as
Under:
S201, the light that the wideband light source 101 issues are entered by the port a of first fiber coupler 103, are passed through
First fiber coupler, 103 beam splitting is clockwise transmission CW light and counterclockwise transmission CCW light, and the CW light is by the first optical fiber
The port c of coupler 103 exports, and the CCW light is exported by the port d of the first fiber coupler 103；
S202, the CW light passes through the variable optical attenuator 104, second fiber coupler 106, described in arrival
Optical frequency shifter 107 reaches diaphragm-type optical-fiber sound pressure sensor 20 after the optical frequency shifter 107 and the optical fiber remove inclined device；
S203, the CCW light is by the fiber delay line 105, second fiber coupler 106, the arrival light
Frequency shifter 107 reaches diaphragm-type optical-fiber sound pressure sensor 20 after the optical frequency shifter 107 and the optical fiber remove inclined device；
S204, the light being reflected back by graphite film in the diaphragm-type optical-fiber sound pressure sensor 20, passes through institute by optical fiber 109
State 106 coupled back into optical fibers link of the second fiber coupler；
S205, the CW light reach first along 2 ports of second fiber coupler 106, by fiber delay line 105
The port d of fiber coupler 103, the CCW light pass through variable optical attenuator 104 along 1 port of the second fiber coupler 106
Reach the port c of the first fiber coupler 103；
S206 is converged by CW the and CCW light after the first fiber coupler 103 in the port b of the first fiber coupler 103
Interference is closed, electric signal is converted by the photodetector 102, can directly export the electric signal to the signal and analyze
Module；
S207, the electric signal that the signal analysis module exports the photodetector 102 are analyzed and processed.
Its working principle, details are as follows:
Graphite film acoustic pressure probe 200 using reflective mode operation is linked into demodulating system and as improved Sagnac optical fiber
A part of loop.Fiber delay line, Sagnac light are introduced by 2 ports in the port d of coupler 103 and coupler 106
The time that CW and CCW light in fine loop reaches film will have a time difference τ.Do not considering variable optical attenuator
In the case where tail optical fiber length, which is determined by the length L of fiber delay line 105, and meets following relationship:
τ=nL/c (1)
Therefore, when the external world has dynamic sound pressure signal to generate the deformation changed over time to graphite film 201, due to Saganc
CW with CCW light reaches the time difference of graphite film in optical fiber loop, thus the film deformation experienced is not also identical.Assuming that film
The shape that the acoustic pressure that piece is subject to occurs becomes u (t)=u0cos(wsT), wherein u0For diaphragm deformation amplitude, w caused by sound wavesIt is
The angular frequency of state acoustic pressure；The diaphragm deformation equivalent phase variation introduced to Sagnac optical fiber loop can be expressed asWhereinFor phase change amplitude caused by sound wave, it is proportional to diaphragm deformation amplitude caused by sound wave
u0；Therefore the phase change between CW and CCW light is poorMeet following relationship,
WhereinIt is the offset phase generated by optical frequency shifter frequency 107, and meets following relationship,
Wherein L is the length of fiber delay time 105, and n is the refractive index of optical fiber, and c is the light velocity in vacuum, and δ f is optical frequency shifter
Frequency displacement size.When the amplitude of extraneous sound pressure signalIt changes, CW and CCW light phase is poorSize changes
Become, so as to cause the variation for the luminous intensity I that photodetector detects.Luminous intensity I and phase differenceMeet such as ShiShimonoseki
System,
Wherein I0For the intensity of input light.Bring formula (2) into formula (4), available output intensity is,
Generate optical frequency shifter inclined by adjusting the length of optical frequency shifter frequency or fiber delay line according to formula (5)
Set phase satisfactionWorking sensor can be made in best operating point, obtain max line
Sex work area and maximum sensitivity.When acoustic signals amplitude is smaller, light phase caused by film deformation changesIt is then public
AC portion in formula (5) is,
Therefore, pass through the variation I of detection output light intensityac, so that it may obtain the phase that acoustic pressure acts on lower institute's colorimetric sensor films
Position variation, to demodulate sound pressure signal.Available, the intensity variation I from formula (6)acSize and frequency dependence, work as acoustic pressure
Signal frequency wsMeet relationship wsWhen=π/τ, IacMaximum, system have peak signal output.When signal frequency is much smaller than π/τ,
IacReduce, the output signal of system also reduces accordingly.Therefore, which is suitable for the signal detection within the scope of certain frequency.
The time difference τ that CW and CCW light reaches film is adjusted by optical fiber extensions 105, makes its frequency w with sound wave to be detectedsMeet and closes
It is ws=π/τ can make system sensitivity maximum.When sound wave is not single-frequency signals, the responsiveness of different frequency component
Will be different, but there is determining sin (wsτ/2) dependence, therefore can be corrected by the method for subsequent processing.
In the present embodiment, having the beneficial effect that using the phase demodulator 10:
One, it by using SLD low-coherence light source 101, effectively relevant caused by reflected light in reduction system can make an uproar
Sound；
Two, inclined device 108 is gone by using optical fiber, can effectively eliminate environment and light polarization state is disturbed and bring signal
It is unstable；
Three, the phase bias of sensor carries out frequency displacement reality to CW the and CCW light in Sagnac fiber optic loop by optical frequency shifter
It is existing.Since optical frequency shifter 107 is placed among 4 ports and optical fiber depolarizer 108 of second fiber coupler 106, can make
The biasing of stable phase angle provided by optical frequency shifter, not by the length of the connection optical fiber 109 of access diaphragm-type optical-fiber sound pressure sensor 20
The influence of degree；
Four, since Sagnac fiber optic loop CW and CCW light transmits in identical fiber path, itself has anti-glitch
Ability, while the quadrature phase biasing that provides to diaphragm-type optical-fiber sound pressure sensor 20 of Sagnac fiber optic loop and film deformation without
It closes, thus greatly reduces external environment (such as air-flow, temperature) to sensor caused by the disturbance of highly sensitive graphite film
Operating point drift.
In conclusion this phase bias presentation mode, eliminates complicated dynamic phasing regulation, so that based on highly sensitive
The diaphragm-type optical-fiber sound pressure sensor 20 for spending film being capable of long-term stable operation.
Embodiment two
Fig. 3 is the preferable structural schematic diagram of phase demodulator 10 provided in an embodiment of the present invention, and details are as follows:
The port a of first fiber coupler 103 connects the wideband light source 101, and the port b connects the photodetection
Device 102, the port c connect 104 first end of fiber delay line, and the port d connects the first of the variable optical attenuator 105
End；
1 port of second fiber coupler 106 connects 104 second end of fiber delay line, described in the connection of 2 ports
The second end of variable optical attenuator 105,3 ports are disappear reflecting the idle end of light processing, and 4 ports connect the optical fiber light
The first end of frequency shifter；
The second end of the optical fiber optical frequency shifter connects 108 first end of optical fiber depolarizer, and the optical fiber depolarizes
The external optical fiber of 108 second end of device, to connect the diaphragm-type optical-fiber sound pressure sensor 20.
The methods of cut by index-matching fluid and oblique angle, 3 ends of second fiber coupler 106 can be effectively reduced
Oral reflex light is to demodulating system bring crosstalk.
Optical frequency shifter 107 is among 4 ports and optical fiber depolarizer 108 of second fiber coupler 106, can be made
Stable phase difference is generated between CW and CCW light, by changing optical frequency shifter shift frequency amount or 105 length of fiber delay line, is made
The phase difference be equal to 2m π+pi/2, m=0,1,2 ..., thus make diaphragm-type optical-fiber sound pressure sensor 20 work quadrature phase bias
Point obtains the output of stable and maximum signal.
In the present embodiment, the diaphragm-type optical-fiber acoustic pressure sensing that the biasing of stable phase angle provided by optical frequency shifter is not accessed
The influence of connection 109 length of optical fiber of device 20, substantially increases the applicability of demodulating system, while can be adapted for long-range acoustic pressure
Sensor.
Embodiment three
Fig. 4 is the structural block diagram of optical fiber sound pressure demodulating system provided in an embodiment of the present invention, and details are as follows:
The phase demodulator 10 is connected using optical fiber and based on the diaphragm-type optical-fiber sound pressure sensor 20 of graphene diaphragm.
Wherein, diaphragm-type optical-fiber sound pressure sensor 20 connects the phase demodulator 10 using optical fiber, and passes through graphene
Diaphragm reflected light.
Fig. 5 is the structural schematic diagram of optical fiber sound pressure demodulating system provided in an embodiment of the present invention.
Fig. 6 is the implementation flow chart of the demodulation method provided in an embodiment of the present invention based on optical fiber sound pressure demodulating system, in detail
It states as follows:
The diaphragm-type optical-fiber sound pressure sensor is linked into Sagnac fiber optic loop with reflective mode operation by S601；
S602, by the optical frequency shifter to the CW light and the asymmetric frequency of CCW light progress in the Sagnac fiber optic loop
Rate is mobile, so as to generate stable phase difference between CW and CCW light；
S603 makes described phase difference etc. by changing the shift frequency amount of the optical frequency shifter or the length of fiber delay line
In 2m π+pi/2, wherein m is natural number；
S604 demodulates the output optical signal of the Sagnac fiber optic loop, obtains acoustic pressure to be measured.
It is optical fiber sound pressure demodulating system provided in an embodiment of the present invention with reference to Fig. 7, Fig. 7, output signal power spectrum is preferable
Sample figure.
In Fig. 7, the sound pressure signal frequency applied is 5kHz, amplitude 800mPa.System output signal-to-noise ratio be
45dB, corresponding minimum detectable sound pressure level are~450 μ Pa/Hz1/2(the detector resolution bandwidth used is 100Hz).
It with reference to Fig. 8, Fig. 8 is optical fiber sound pressure demodulating system provided in an embodiment of the present invention, output signal power is at any time
Change preferable sample figure.
In fig. 8, the diaphragm-type optical-fiber sound pressure sensor 20 using phase demodulating system of the invention is given, it is right
The response of 5kHz, 800mPa sound pressure signal changes with time；The signal output of the sensor-based system, which is floated, is less than 0.35dB.
In addition, adjusting the intensity of CW and CCW light in Sagnac optical fiber loop, Ke Yiyou by variable optical attenuator 104
Effect eliminates influence of the diaphragm reflectivity changes to output signal amplitude in different membrane sensors, makes the demodulating system usability
More preferably；Optical frequency shifter 107 is placed between fiber coupler 106 and optical fiber depolarizer 108 simultaneously, optical frequency shifter can be made
The stable phase angle biasing of offer is not connected the effect length of optical fiber 109 by sensor, to be suitble to long-range sound pressure measurement.
Acoustic pressure sensor-based system of the invention passes through the diaphragm of submicrometer-thick based on above-mentioned phase demodulating system
Formula optical fibre sound pressure sensor 20 is changed using transmission light phase caused by the deformation that acoustic pressure to be measured generates film is detected, real
The high-precision and high stability measurement of existing acoustic pressure；Large scale and very thin graphite film can effectively improve diaphragm-type optical-fiber acoustic pressure
The sensitivity of 20 acoustic pressure of sensor；It is inclined to provide stable phase using the optical frequency shifter improved in Sangac optical fiber ring structure
It sets, enables 20 long-term work of diaphragm-type optical-fiber sound pressure sensor in best operating point, eliminate for traditional Fabry-Perot
Interfere complexity dynamic phasing feedback regulation process used by sound pressure sensor.By the way that optical frequency shifter 107 is placed on second in Fig. 3
Among 4 ports of a fiber coupler 106 and optical fiber depolarizer 108, stable phase angle provided by optical frequency shifter can be kept inclined
It sets, is not influenced by the length of the connection optical fiber 109 of access diaphragm-type optical-fiber sound pressure sensor 20, substantially increase demodulating system
Applicability, while can be adapted for the sensor of long-range acoustic pressure.
Above-mentioned demodulating system is applicable not only to above-mentioned diaphragm-type optical-fiber sound pressure sensor 20, is also other reflective operation moulds
The fibre optical sensor of formula provides phase demodulating scheme.
Example IV
Fig. 9 is the structural schematic diagram of diaphragm-type optical-fiber sound pressure sensor 20 provided in an embodiment of the present invention, and details are as follows:
The diaphragm-type optical-fiber sound pressure sensor 20 includes:
According to dynamic sound pressure signal, the graphite film of the deformation changed over time is generated；
The supporter of the fixed graphite film；
Positioned at the side of the supporter, the air equalizer opening of equilibrium air pressure；
Positioned at the center of the supporter, the optical fiber fixed hole of optical fiber is connected.
The diaphragm-type optical-fiber sound pressure sensor 20 of the embodiment of the present invention, including with a through-hole 202 and circular groove 205
The optical fiber 204 of sensor body 203, graphite film 201, end face with inclination angle；Wherein, graphite film 201 is attached at sensor
203 top circular groove of body, 205 end face, optical fiber 204 is from the outer via through holes 202 of sensor body 203 and is through to the another of through-hole 202
End, close to graphite film 201；It conducts optical fiber 204 and transmits light to graphite film 201, and receive 201 central plane of graphite film
Reflected light.
The chamber decision design of 203 top braces graphite film 201 of the sensor body is circle, and diameter is as needed
It can be from several hundred microns to several millimeters；Through-hole 202 is preferably designed to circular through hole, easy to process, and general with optical fiber 204
Cylindrical adaptation can form relatively good coincide；The diameter of through-hole is preferably designed to 127 according to the diameter of optical fiber 204
μm, this aperture is conducive to the fixation of optical fiber 204；The needs of environment are detected according to acoustic pressure, the sensor body 203 can be selected
Zirconium oxide or quartz material；Optical fiber 204 is cut using single mode optical fiber, and the tilt angle of fiber end face is preferentially selected after cutting
8 degree are selected as, to minimize the reflected light of optical fiber end.Optical fiber 204 is inserted into above-mentioned through-hole 202, is then used
Under the monitoring of optical microscopy, optical fiber 204 is further adjusted at a distance from graphene film 201, until distance between the two
Degree is suitable.It is finally using epoxide-resin glue that optical fiber 204 is fixed in through-hole 202, diaphragm type acoustic pressure sensing head can be formed.
Wherein, the sensor body 203 of the present invention is the support construction of sensor, for carrying graphite film 201, and is drawn
Lead and fix optical fiber 204.The shape of sensor body 203 can be cylindrical or rectangle.For the ease of easy to process and shape
Shape is stablized, and processing forms circular groove 205 and the guidance of above-mentioned support graphite film on the axial direction of sensor body 203
The through-hole 202 of optical fiber 204.
Optical fiber 204 is used for transmission incident light needed for sound pressure measurement process and reflected light.
Further, in the above-described embodiment, graphite film 201 uses submicrometer-thick, the thickness of submicron order
Degree is so that it can generate bigger deformation under acoustic pressure effect, to keep sensor sensitiveer.
Diaphragm-type optical-fiber sound pressure sensor 20 of the invention deforms institute by the graphite film 201 under detection acoustic pressure effect
Caused transmission light phase variation is to test sound pressure measurement.Compared to existing Fabry-Perot interference measurement method, sensing
Device production aspect does not need simply more accurately to control the distance between fiber end face and film.In terms of signal detection, it is not required to
The operation wavelength for adjusting laser makes working sensor in orthogonal operating point.
Embodiment five
Figure 10 is the manufacture stream of diaphragm type sound pressure sensor 20 in optical fiber sound pressure demodulating system provided in an embodiment of the present invention
Cheng Tu, details are as follows:
S101 prepares graphite film；
S102, the bore edges by the graphite film along supporter are fixed；
S103, in the side of supporter, process air pressure balance hole；
Optical fiber fixed hole is arranged at the center of supporter in S104；
Section is handled the optical fiber for inclined-plane by S105, through the optical fiber fixed hole close to the graphite film, adjusts institute
Optical fiber is stated at a distance from the graphite film, and the optical fiber is fixed, the diaphragm-type optical-fiber acoustic pressure can be obtained and pass
Sensor 20.
Through the above description of the embodiments, it is apparent to those skilled in the art that the present invention can borrow
Help software that the mode of required common hardware is added to realize.The program can store in read/write memory medium, described
Storage medium, as random access memory, flash memory, read-only memory, programmable read only memory, electrically erasable programmable storage
Device, register etc..The storage medium is located at memory, and processor reads the information in memory, executes this hair in conjunction with its hardware
Method described in bright each embodiment.
The above description is merely a specific embodiment, but scope of protection of the present invention is not limited thereto, any
In the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by those familiar with the art, all answers
It is included within the scope of the present invention.Therefore, protection scope of the present invention should be subject to the protection scope in claims.
Claims (10)
1. a kind of phase demodulator, using the structure of Sagnac fiber optic loop, external diaphragm-type optical-fiber sound pressure sensor, including broadband
Light source, photodetector connect the photodetector, receive the signal analysis mould of the electric signal of the photodetector output
Block, which is characterized in that the phase demodulator further include:
It is separately connected the wideband light source and the photodetector, the light that wideband light source described in beam splitting issues is to pass clockwise
First fiber coupler of defeated CW light and counterclockwise transmission CCW light；
Connect first fiber coupler, adjust the intensity of the CW light, or adjust the CCW light intensity it is tunable
Optical attenuator；
Connect the fiber delay line of first fiber coupler；
It is separately connected the fiber delay line and the variable optical attenuator, couples the diaphragm-type optical-fiber sound pressure sensor
Second fiber coupler of the light of reflection；
Second fiber coupler is connected, the optical frequency shifter of stable pi/2 quadrature phase biasing is provided；
The optical frequency shifter is connected, and passes through the optical fiber depolarizer of the external diaphragm-type optical-fiber sound pressure sensor of optical fiber.
2. phase demodulator as described in claim 1, which is characterized in that the port a of first fiber coupler connects institute
Wideband light source is stated, the port b connects the photodetector, and the port d connects the fiber delay line first end, and the port c connects institute
State the first end of variable optical attenuator；
1 port of second fiber coupler connects the second end of the variable optical attenuator, and 2 ports connect the optical fiber
Delay line second end, 3 ports are disappear reflecting the idle end of light processing, and 4 ports connect the first of the optical fiber optical frequency shifter
End；
The second end of the optical fiber optical frequency shifter connects the optical fiber depolarizer first end, the optical fiber depolarizer second end
External optical fiber, to connect the diaphragm-type optical-fiber sound pressure sensor.
3. phase demodulator as described in claim 1, which is characterized in that first fiber coupler and the second fiber coupling
Device is the identical fiber coupler of splitting ratio.
4. phase demodulator as described in claim 1, which is characterized in that the fiber coupler includes 3dB fiber coupler.
5. phase demodulator as described in claim 1, which is characterized in that the optical frequency shifter is located at the fiber coupler
Between the optical fiber depolarizer.
6. phase demodulator as described in claim 1, which is characterized in that the optical fiber depolarizer uses length ratio for 1:2,
Fast axle is formed at two sections of polarization maintaining optical fibre weldings at 45 degree of angles；Alternatively,
Use length than being formed for 1:2, slow axis at two sections of polarization maintaining optical fibre weldings at 45 degree of angles.
7. a kind of optical fiber sound pressure demodulating system, including phase demodulator described in claim 1 to 5 any one claim,
It is characterized in that, the optical fiber sound pressure demodulating system further include:
The phase demodulator is connected using optical fiber and based on the diaphragm-type optical-fiber sound pressure sensor of graphene diaphragm.
8. a kind of demodulation method based on optical fiber sound pressure demodulating system as claimed in claim 7, which is characterized in that the demodulation side
Method includes:
The diaphragm-type optical-fiber sound pressure sensor is linked into Sagnac fiber optic loop with reflective mode operation；
By the optical frequency shifter in the Sagnac fiber optic loop CW light and CCW light carry out asymmetric frequency shifts, with
Make to generate stable phase difference between CW and CCW light；
By the shift frequency amount of the change optical frequency shifter or the length of fiber delay line, the phase difference is made to be equal to 2m π+pi/2,
Wherein, m is natural number；
The output optical signal for demodulating the Sagnac fiber optic loop, obtains acoustic pressure to be measured.
9. optical fiber sound pressure demodulating system as claimed in claim 7, which is characterized in that the diaphragm-type optical-fiber sound pressure sensor packet
It includes:
According to dynamic sound pressure signal, the graphite film of the deformation changed over time is generated；
The supporter of the fixed graphite film；
Positioned at the side of the supporter, the air equalizer opening of equilibrium air pressure；
Positioned at the center of the supporter, the optical fiber fixed hole of optical fiber is connected.
10. a kind of manufacturing method based on diaphragm type sound pressure sensor in optical fiber sound pressure demodulating system described in claim 7, including
Following steps:
Prepare graphite film；
The graphite film is fixed along supporter bore edges；
In the side of supporter, process air pressure balance hole；
At the center of supporter, optical fiber fixed hole is set；
Section is handled into the optical fiber for inclined-plane, through the optical fiber fixed hole close to the graphite film, adjust the optical fiber with
The distance of the graphite film, and the optical fiber is fixed, the diaphragm-type optical-fiber sound pressure sensor can be obtained.
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| CN109115688B (en) * | 2018-09-10 | 2020-11-03 | 大连理工大学 | Optical fiber remote measuring type multifunctional gas leakage listening instrument and method |
| CN114844574B (en) * | 2022-07-04 | 2022-10-18 | 浙江大学湖州研究院 | Optical fiber communication system and communication method |
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