CN102853920B - High-sensitivity Mach-Zahnder interference system - Google Patents
High-sensitivity Mach-Zahnder interference system Download PDFInfo
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- CN102853920B CN102853920B CN201210376429.1A CN201210376429A CN102853920B CN 102853920 B CN102853920 B CN 102853920B CN 201210376429 A CN201210376429 A CN 201210376429A CN 102853920 B CN102853920 B CN 102853920B
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Abstract
The invention discloses a high-sensitivity Mach-Zahnder interference system, which is characterized in that a broad-spectrum light source is connected with a first port of a circulator through an optical fiber, a second port of the circulator is connected with one end of an acousto-optic modulator through an optical fiber, a signal generator is connected with the acousto-optic modulator to supply a pulse signal, the other end of the acousto-optic modulator is connected with the input end of a first optical-fiber coupler through an optical fiber, two output optical fibers of the first optical-fiber coupler are connected with a sensing optical-fiber ring and a reference optical-fiber ring and additionally provided with a first polarization controller, a third port of the circulator is connected with a light spectrum analyzer, and the phase difference corresponding to the two optical-fiber rings is measured by outputting the light spectrum; and the sensing optical-fiber ring and the reference optical-fiber ring are respectively formed by joining the input ends and the output ends of a second coupler and a third coupler, and the length of the sensing optical-fiber ring is identical to that of the reference optical-fiber ring. Multiple times of optical oscillation inside the optical-fiber rings are utilized to accumulate the phase variation of the optical fibers, so that the measurement sensitivity is greatly improved. In addition, the wavelength division multiplexing can be realized.
Description
Technical field
The present invention relates to once moral interference system of a kind of high sensitivity Mach.
Background technology
Mach-Zehnder interferometer is widely used in Fibre Optical Sensor, optical fiber communication.
Conventional Mach-Zehnder interferometer two arm optical path differences have intensity and two kinds of demodulation methods of spectrum, the sensitivity of intensity demodulation is very high, but the monochromaticity of light source, frequency stability, power stability are had to larger requirement, measurement result can be subject to the impact of polarisation of light state simultaneously, needs to overcome the problem of stability in practical process.
The sensitivity of spectrum demodulation is not high, but demodulation mode is simple, and light source is used common wide spectrum light source, less demanding to the power stability of light source.The acquisition methods of interference spectrum mainly contains two kinds, and a kind of is directly to use spectrometer measurement interference spectum; Another is at wide spectrum light source output terminal, to add the device of a meticulous length scanning of FP, and receiving end is used power probe probe power to change, and by output waveform, is changed and is obtained.It is convenient directly compared with the second that first method obtains interference spectum, but within the long period of spectrometer scanning wavelength, interference spectum can drift about, and this can reduce measuring accuracy.It is low that second method has cost, and response is fast, but owing to controlling the nonlinear characteristic of the long PZT in FP chamber, need to use etalon and FBG to carry out wavelength scaling.
After getting spectrum, can realize by the position at detected peaks peak separation or single peak the demodulation of optical path difference, but because interference spectum is sinusoidal pattern function, so there is very large error in peak value location.For single peak, although come measurement of optical path difference to have very high sensitivity by the level time of peak wavelength and its correspondence, the inferior measurement of level easily produces error, so these two kinds of method precision are still not high.Professor Jiang Yi of Beijing Institute of Technology has proposed the demodulation method based on Fourier transform, and this method has advantages of that precision is high.But this method needs more complicated signal processing.
Summary of the invention
Technical matters to be solved by this invention is to provide once moral interference system of a kind of high sensitivity Mach, for Fibre Optical Sensor.
High sensitivity Mach of the present invention once moral interference system comprises wide spectrum light source, optical fiber circulator, acousto-optic modulator, signal generator, first, second, third fiber coupler, the first Polarization Controller, spectroanalysis instrument.
Described wide spectrum light source connects the first port of circulator by optical fiber, the second port of circulator connects acousto-optic modulator one end by optical fiber, signal generator connects acousto-optic modulator provides pulse signal, the other one end of acousto-optic modulator connects the first fiber coupler input end by optical fiber, two output optical fibres of the first fiber coupler connect sensing fiber ring, reference optical fiber ring, and add the first Polarization Controller, the 3rd port of circulator connects spectroanalysis instrument, by output spectrum, measures two corresponding phase differential of fiber optic loop; Described sensing fiber ring, reference optical fiber ring are respectively second, third coupling mechanism input/output terminal and connect to form, and described sensing fiber ring and reference optical fiber ring length equate.
The coupling ratio of described the first fiber coupler is 1:1; The splitting ratio of described second, third coupling mechanism is identical, is 1:99～1:9 respectively, and the equal corresponding high coupling ratio of the insertion loss between the two-port in described sensing fiber ring.
Described high sensitivity Mach once moral interference system also comprises the second Polarization Controller, the 3rd Polarization Controller, and described sensor fibre and reference optical fiber add second, third Polarization Controller respectively.
The pulse signal that described signal generator provides is that dutycycle, cycle are adjustable.
Described high sensitivity Mach once moral interference system also comprises all equal first wave division multiplexer, Second Wave division multiplexers of two bandwidth wavelength, the common port of described first, second wavelength division multiplexer connects described the first fiber coupler, the 3rd fiber coupler by optical fiber respectively, the multiplexing end of described first, second wavelength division multiplexer is relative, adds respectively between two described sensing fiber ring in multiplexing end between same channel.Because different fiber ring is in different channels, finally by wave bands different on output spectrum, independently carry out demodulation, realize the wavelength-division multiplex of sensing fiber ring.
Described Mach once moral principle of interference is: wide spectrum optical, through being modulated into pulsed light in AOM intensity, after input the first fiber coupler, can transmit along clockwise and counterclockwise both direction.The light pulse of transmission can be owing to forming two pulse trains in being coupled to optical fiber ring cavity when by second, third fiber coupler clockwise; Because two fiber optic loop are equal in length, second, third fiber coupler coupling ratio is equal, and two pulse trains are overlapping in time, and upper corresponding pulse power of every two times equates.Light also can produce upper overlapping pulse train of two times equally, counterclockwise.These four pulse trains finally arrive spectrometer by bis-intensity modulated of AOM through circulator.
The clockwise pulsed light of exporting from the first fiber coupler vibrates and can form one group of light pulse sequence in sensing fiber ring, and pulse power decays according to the loss of fiber optic loop individual pen; And it is directly high a lot of than first light pulse of pulse train (being called for short 1 rank pulse) by the pulse power of the second fiber coupler, then the pulse that this power is higher is through the 3rd fiber coupler, one group of light pulse sequence of same formation, the m rank pulse of these two pulse trains is overlapping in time, and is all in corresponding ring, vibrate m time and form; Latter two pulse train arrives the first fiber coupler input end simultaneously, AOM is just in next pulse and produces state, be the logical state of light, just allow two m rank pulses finally enter spectrometer by AOM, on spectrometer, will record so the spectrum of these two pulse interference gained.
Same pulse of propagating counterclockwise also can finally obtain the spectrum that two m rank pulse interference obtain.And because light path is identical, the interference spectrum of gained with obtain clockwise consistent.The phase differential of these two m rank pulses is m times of 1 rank pulse phase difference.
Therefore, sensing fiber ring length l
1and the relation between interference spectrum can be expressed as:
Here, l
1, l
2be respectively the length of sensing fiber ring and reference optical fiber ring, l
1≈ l
2, the effective refractive index that n is fiber core, λ
1and λ
2be respectively two adjacent peak wavelengths of interference spectum or valley wavelength.By formula (1), just can demodulate sensor fibre phase place by interference spectum changes.
Beneficial effect of the present invention is:
1, the present invention compares with traditional double light path Mach-Zehnder interferometer, utilizes light multiple oscillation in fiber optic loop, and accumulation fiber phase changes, and makes to measure sensitivity and greatly improves;
2, the present invention can, by using wavelength division multiplex device, realize wavelength-division multiplex.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, technical scheme of the present invention is further described in detail.
Fig. 1 is that high sensitivity Mach Zeng Degan of the present invention relates to system construction drawing;
Fig. 2 is the structural drawing of transducing part optical fiber ring cavity of the present invention;
Fig. 3 has provided the multiplexing schematic diagram of sensing fiber ring;
Embodiment
Fig. 1 has provided high sensitivity Mach Zeng Degan and has related to system construction drawing, and wide spectrum light source 1 output light is by the first port of optical fiber circulator 2, and the second port of optical fiber circulator 2 connects acousto-optic modulator 3, and the 3rd port of optical fiber circulator 2 connects spectrometer 4.Signal generator 5 connects acousto-optic modulator 3 and provides duty cycle adjustable pulse signal.The coupling ratio that acousto-optic modulator 3 other ends access the first fiber coupler 6, the first fiber couplers is 1:1.Two output terminals of the first fiber coupler 6 are connected by welding mode with two optical fiber ring cavities.On the optical fiber connecting at second, third fiber coupler, add 9, two optical fiber ring cavities of the first Polarization Controller respectively by second, third fiber coupler 7,8 input/output terminal weldings and add second, third Polarization Controller 10,11 to form.
In Fig. 1, the requirement of the pulse signal sending of signal source 5 is the time that pulse width is less than light transmission one circle in fiber optic loop, and cycle size is
here l
1for sensor fibre ring length, l
3be the first fiber coupler output tail optical fiber and two fiber optic loop tail optical fiber total lengths and, l
4for the fiber lengths of AOM to the first fiber coupler, c is the light velocity in vacuum, and m is integer.
In Fig. 1, the first Polarization Controller 9 is used for eliminating the interference of the both direction pulse causing due to fiber birefringence.Second, third Polarization Controller 10,11 is used for adjusting two corresponding m of ring rank pulse, makes the contrast of exporting interference spectum reach maximum.
Fig. 2 has provided transducing part fiber optic loop cavity configuration figure, optical fiber ring cavity is 1:99 by two splitting ratios and forms to second, third fiber coupler 7,8 1:9, concrete method of attachment is identical, if two input ends of fiber coupler in Fig. 2 are A, B, two output terminals are C, D, AC and BD are straight-through arm, insertion loss corresponding high coupling ratio, for example 0.1dB(99% at the BD two ends in access ring), 0.5dB(90%).
Fig. 3 has provided the multiplexing schematic diagram of sensing fiber ring, first, second wavelength division multiplexer 12,13 is respectively all equal wavelength division multiplexer WDM of two bandwidth wavelength, the common port of first, second wavelength division multiplexer 12,13 connects the first fiber coupler 6, the 3rd fiber coupler 8 by optical fiber respectively, the multiplexing end of first, second wavelength division multiplexer 12,13 is relative, in multiplexing end, between same channel, respectively add between two a fiber optic loop described in Fig. 2.And the length of each sensing fiber ring of different channels equates with reference optical fiber ring length, the incoming fiber optic length 14 outside sensing fiber ring also equates respectively, so just realizes the multiplexing of a plurality of fiber optic loop.For the light of clockwise propagation, different wave length enters different channels by 12, through different reference optical fiber rings, finally by 13, converges in an optical fiber again.For the light of counterclockwise propagation, different wave length enters different channels by 13, through different reference optical fiber rings, finally by 12, converges in an optical fiber again.Wavelength corresponding to the different channels observed in spectrometer is with regard to the phase information of corresponding different sensing fiber rings.
It should be noted last that, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement technical scheme of the present invention, and not departing from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of claim scope of the present invention.
Claims (5)
1. a high sensitivity Mach moral interference system once, is characterized in that, comprises wide spectrum light source, optical fiber circulator, acousto-optic modulator, signal generator, first, second, third fiber coupler, the first Polarization Controller, spectroanalysis instrument;
Described wide spectrum light source connects the first port of circulator by optical fiber, the second port of circulator connects acousto-optic modulator one end by optical fiber, signal generator connects acousto-optic modulator provides pulse signal, the other one end of acousto-optic modulator connects the first fiber coupler input end by optical fiber, two output optical fibres of the first fiber coupler connect sensing fiber ring, reference optical fiber ring, and add the first Polarization Controller, the 3rd port of circulator connects spectroanalysis instrument, by output spectrum, measures two corresponding phase differential of fiber optic loop; Described sensing fiber ring, reference optical fiber ring are respectively second, third coupling mechanism input/output terminal and connect to form, and described sensing fiber ring and reference optical fiber ring length equate;
The requirement of the pulse signal sending of described wide spectrum light source is the time that pulse width is less than light transmission one circle in fiber optic loop, and cycle size is
l
1for sensor fibre ring length, l
3be the first fiber coupler output tail optical fiber and two fiber optic loop tail optical fiber total lengths and, l
4for the fiber lengths of AOM to the first fiber coupler, c is the light velocity in vacuum, and m is integer;
Sensing fiber ring length l
1and the pass between interference spectrum is:
Here, l
1, l
2be respectively the length of sensing fiber ring and reference optical fiber ring, l
1≈ l
2, the effective refractive index that n is fiber core, λ
1and λ
2be respectively two adjacent peak wavelengths of interference spectum or valley wavelength; By formula (1), just can demodulate sensor fibre phase place by interference spectum changes.
2. high sensitivity Mach according to claim 1 moral interference system once, is characterized in that, the coupling ratio of described the first fiber coupler is 1:1; The splitting ratio of described second, third coupling mechanism is identical, is 1:99～1:9 respectively, and the equal corresponding high coupling ratio of the insertion loss between the two-port in described sensing fiber ring.
3. high sensitivity Mach according to claim 2 moral interference system once, is characterized in that, also comprise the second Polarization Controller, the 3rd Polarization Controller, described sensor fibre and reference optical fiber add second, third Polarization Controller respectively.
4. according to the moral interference system once of the high sensitivity Mach one of claim 1-3 Suo Shu, it is characterized in that, the pulse signal that described signal generator provides is that dutycycle, cycle are adjustable.
5. high sensitivity Mach according to claim 4 moral interference system once, it is characterized in that, also comprise all equal first wave division multiplexer, Second Wave division multiplexers of two bandwidth wavelength, the common port of described first, second wavelength division multiplexer connects described the first fiber coupler, the 3rd fiber coupler by optical fiber respectively, the multiplexing end of described first, second wavelength division multiplexer is relative, adds respectively between two described sensing fiber ring in multiplexing end between same channel.
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| CN103542925B (en) * | 2013-09-23 | 2015-05-20 | 华中科技大学 | Quasi-distributed optical vibrating sensing device |
| CN104729548A (en) * | 2015-02-11 | 2015-06-24 | 宁波诺可电子科技发展有限公司 | Bio-directional common optical path distributed fiber optic interferometer |
| CN105806468A (en) * | 2016-05-06 | 2016-07-27 | 华中科技大学 | Fiber bragg grating vibration sensor and detection device thereof |
| CN106546177B (en) * | 2016-10-24 | 2019-05-31 | 金陵科技学院 | It is a kind of measurement fiber coupler tail optical fiber length difference away from system and method |
| CN108036728A (en) * | 2017-12-14 | 2018-05-15 | 大连理工大学 | A kind of phase difference solution mode fiber optics displacement measuring method and instrument |
| CN110057543B (en) * | 2019-04-24 | 2020-12-11 | 暨南大学 | Wave surface measuring device based on coaxial interference |
| CN113091603A (en) * | 2021-04-01 | 2021-07-09 | 深圳大学 | Interference device with adjustable free spectral range |
| CN113938201B (en) * | 2021-09-18 | 2023-02-10 | 华中科技大学 | Optical fiber network |
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| CN101298992A (en) * | 2008-06-05 | 2008-11-05 | 西北工业大学 | Distributed type fiber optic sensor based on optical fiber cavity attenuation and vibration technique |
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