CN108844717A - A kind of measurement method of fibre optic interferometer arm length difference - Google Patents
A kind of measurement method of fibre optic interferometer arm length difference Download PDFInfo
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- CN108844717A CN108844717A CN201810560911.8A CN201810560911A CN108844717A CN 108844717 A CN108844717 A CN 108844717A CN 201810560911 A CN201810560911 A CN 201810560911A CN 108844717 A CN108844717 A CN 108844717A
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
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Abstract
The present invention relates to a kind of measurement method based on fibre optic interferometer brachium difference measuring device, mainly solve the problems, such as that the existing measuring system stability using optical interference method is not high and measurement accuracy is low.This measurement method is interfered by double frequency combs in microwave domain, and interference signal is measured with frequency spectrograph, the arm length difference of testing fiber interferometer can be obtained by the bandwidth in interference signal a cycle, simultaneously the variation of measurement accuracy can be realized by changing the frequency interval of frequency comb, improve the stability of measurement accuracy and system, the shortcomings that cannot achieve big brachium difference measurements using the method for optical interference is compensated for, workflow is simple, and replicability is strong.
Description
Technical field
The present invention relates to fibre optical sensor performance test measurement methods, more particularly to a kind of fibre optic interferometer arm length difference
Measurement method.
Background technique
Fibre optic interferometer is communicated with its excellent performance in fiber optic temperature, vibrating sensing, fibre optic hydrophone and quantum key
Equal fields have a wide range of applications.Interferometer two-arm arm length difference directly determines the measurement sensitivity of above-mentioned measurement and communication system
And communication speed, with the fast development of contemporary communication technology and sensor measurement techniques, to the essence of interferometer two-arm arm length difference
Really measurement is of great significance.
Mainly there are White Light Interferometer, coherent light interference striped meter to the measurement of fibre optic interferometer two-arm optical fiber length difference at present
Number the methods of method and microwave photon mixing method, White Light Interferometer pass through to the received each white-light fringe of detector scanning mirror
The accurate measurement of peak position obtains signal light and introduces optical path difference between two arms of interferometer, obtains arm length difference in conversion, but
The length of its scanning range for being limited to scan table, measurable arm length difference is shorter；Coherent light interference Fringe-counting method passes through sight
Interference fringe spacing measurement arm length difference is examined, relative difficulty is implemented；Microwave photon mixing method is by arm length difference signal modulation to light
Carry on microwave phase, demodulation phase measures arm length difference, be able to achieve the measurement of degree of precision, but its structure is complicated, cost compared with
It is high.The invention proposes a kind of measurement methods of new fibre optic interferometer arm length difference, are done by double frequency combs in microwave domain
It relates to, and measures interference signal with frequency spectrograph, it is dry to can be obtained by testing fiber by the bandwidth in interference signal a cycle
The arm length difference of interferometer.
Summary of the invention
The technical problem to be solved in the present invention overcomes existing defect, proposes a kind of survey of new fibre optic interferometer arm length difference
Method and apparatus are measured, the variation of measurement accuracy can be realized by changing the frequency interval of frequency comb, improve the steady of measuring system
Qualitative, the cost of the measuring system is low, and workflow is simple, and measurement range is wide.
The technical solution that the present invention uses to solve above-mentioned technical problem is as follows：The present invention is by using a kind of new light
The measuring device of fine interferometer arm length difference, including narrow linewidth laser, polarization-maintaining fiber coupler, phase-modulator, polarization state control
Device, acousto-optic frequency shifters, fiber coupler, testing fiber interferometer, photodetector, frequency spectrograph, signal processing and display mould processed
Block, microwave signal generator.The light that the frequency of the narrow linewidth laser output is f is divided into two-way by polarization-maintaining fiber coupler
Optical path, optical path 1 and optical path 2；The light of optical path 1 passes through phase-modulator, the frequency of the modulated signal applied on the phase-modulator
Rate is fm, modulated signal provides by microwave signal generator, and the phase-modulator output spectrum will occur with modulating frequency fmFor
A series of sidebands of integral multiple；Likewise, the light of optical path 2 passes through phase-modulator, the modulation applied on the phase-modulator
The frequency of signal is fm+fc, modulated signal provides by microwave signal generator, the phase-modulator output spectrum will occur with
Modulating frequency fm+fcFor a series of sidebands of integral multiple；The light of the phase-modulator output is described using acousto-optic frequency shifters
The frequency of the modulated signal loaded in acousto-optic frequency shifters is fAOM, modulated signal provides by microwave signal generator, the phase tune
For the output light of device processed then after frequency shifter, the frequency of 2 light carrier of optical path becomes f+fAOM；The optical path 1 and optical path 2 are by single
Beat frequency will be generated after mode fiber coupler and forms optical frequency comb, and the frequency interval of the optical frequency comb is fc；If the light
Frequency comb passes through high-speed photodetector direct detection, and what is observed on frequency spectrograph is exactly rf frequency comb；In the optical path 1
The effect of polarization beat length device be that adjust the interference contrast that the polarization state of optical path 1 generates optical path 1 and optical path 2 best, from
And improve the effect of two paths of signals beat frequency.
The testing fiber interferometer can be a Mach Zeng De (M-Z)) structure of interferometer, it is dry to be also possible to Michelson
The structure of interferometer.
The frequency comb enters in testing fiber interferometer after single-mode optical-fibre coupler, and the interferometer to be measured is by shape
It is divided into two-way optical frequency comb at frequency comb, two-way frequency comb occurs dry in frequency comb after the output end combining of interferometer to be measured
It relates to, which just carries the arm length difference information of interferometer to be measured.
The technical solution that the present invention uses to solve above-mentioned technical problem, the work that the present invention is further explained uses are former
Reason, specific measuring principle are as follows：
Measuring principle of the invention is the interference of radiofrequency signal, and frequency comb carries out photoelectric conversion through high-speed photodetector
Afterwards, it exports and is combed for radio frequency, therefore frequency comb can be understood as light and carry radio frequency comb, light carries radio frequency comb by testing fiber interferometer
Afterwards, it will be interfered in microwave domain, the period of the interference signal is determined by interferometer two-arm optical path difference to be measured, and testing fiber is dry
The emergent light of interferometer is represented by：
I (f)=I0[1+cosφ(f)] (1)
I in above formula0To enter the light intensity for injecting interferometer to be measured, phase difference of the φ (f) between interferometer two-arm to be measured can
It is expressed as：
D is interferometer two-arm arm length difference to be measured in above formula, and n is the refractive index of optical fiber, and c is the light velocity.Photodetector receives
To interferometer to be measured export interference signal and be converted into electric signal, observe the electric signal, an available cosine with frequency spectrograph
Microwave signal, the frequency interval Δ f between adjacent two wave crest or trough of the signal are：
Then the arm length difference of interferometer two-arm to be measured is represented by：
From the above equation, we can see that according to light velocity constant c, the signal in a cycle that the refractive index n and frequency spectrograph of optical fiber are obtained
Frequency range Δ f, so that it may obtain the arm length difference of interferometer two-arm to be measured.
The beneficial effects of the present invention are：The measuring system is interfered by double frequency combs in microwave domain, and uses frequency spectrum
Instrument measures interference signal, just can be obtained the arm length difference of testing fiber interferometer by the bandwidth in interference signal a cycle,
Can also realize the variation of measurement accuracy by changing the frequency interval of frequency comb simultaneously, improve measuring system stability and
Measurement accuracy, measurement operation is more simple and easy, and replicability is strong.
Detailed description of the invention
Present invention will be further explained below with reference to the attached drawings and examples.
Fig. 1 is the measuring system block schematic illustration of double passage differential laser phase noise of the present invention；
Fig. 2 is Mach once moral fibre optic interferometer schematic diagram；
Fig. 3 is Michelson fiber-optic interferometer schematic diagram；
In attached drawing：
101, narrow linewidth laser 102, polarization-maintaining fiber coupler 103, phase-modulator
104, polarization beat length device 105, phase-modulator 106, acousto-optic frequency shifters
107, fiber coupler 108, testing fiber interferometer 109, photodetector
201, frequency spectrograph 202, signal processing and display module 203, microwave signal generator
204, microwave signal generator 205, microwave signal generator 301, fiber coupler
302, fiber coupler 401, fiber coupler
Specific embodiment
With reference to the accompanying drawings and detailed description, the present invention is furture elucidated, it should be understood that following specific embodiments are only
For illustrating the present invention rather than limiting the scope of the invention.
A kind of measurement method of fibre optic interferometer arm length difference is interfered in microwave domain by double frequency combs, and uses frequency spectrum
Instrument measures interference signal, can obtain the brachium of testing fiber interferometer by the bandwidth in interference signal a cycle
Difference.
As shown in Figure 1, a kind of measuring device of fibre optic interferometer arm length difference, including narrow linewidth laser 101, polarization-maintaining
Fiber coupler 102, phase-modulator 103, polarization beat length device 104, phase-modulator 105, acousto-optic frequency shifters 106, optical fiber
Coupler 107, testing fiber interferometer 108, photodetector 109, frequency spectrograph 201, signal processing and display module 202, three
A microwave signal generator 203,204,205.
The light that the frequency that the narrow linewidth laser 101 exports is f is divided into two-way light by polarization-maintaining fiber coupler 102
Road, optical path 1, optical path 2；The light of optical path 1 passes through phase-modulator 103, the modulated signal applied on the phase-modulator 103
Frequency is fm, modulated signal provides by microwave signal generator 203, and 103 output spectrum of phase-modulator will occur to adjust
Frequency f processedmFor a series of sidebands of integral multiple；Likewise, the light of optical path 2 passes through phase-modulator 105, the phase-modulator
The frequency of the modulated signal applied on 105 is fm+fc, modulated signal provides by microwave signal generator 204, the phase-modulation
105 output spectrum of device will occur with modulating frequency fm+fcFor a series of sidebands of integral multiple；What the phase-modulator 105 exported
For light using acousto-optic frequency shifters 106, the frequency of the modulated signal loaded on the frequency shifter 106 is fAOM, modulated signal is by microwave
Signal generator 205 provides, and the output light of the phase-modulator 105 is then after frequency shifter 106, the frequency of 2 light carrier of optical path
Rate becomes f+fAOM；The optical path 1 and optical path 2 will generate beat frequency after single-mode optical-fibre coupler 107 and form optical frequency comb,
The frequency interval of optical frequency comb is fcIf the optical frequency comb passes through high-speed photodetector direct detection, seen on frequency spectrograph
What is observed is exactly rf frequency comb, and the effect of the polarization beat length device 104 in the optical path 1 is that the polarization state of adjusting optical path 1 makes
The interference contrast that optical path 1 and optical path 2 generate is best, to improve the effect of two paths of signals beat frequency.
The testing fiber interferometer 108 can be a Mach Zeng De (M-Z)) structure of interferometer, it is also possible to Michael
The structure of inferior interferometer, Mach once moral fibre optic interferometer structure as shown in Fig. 2, 301 and 302 be fiber coupler, 1 and 2 are
Input port, 3 and 4 be output port；As shown in figure 3,401 be fiber coupler, 1 is the structure of Michelson fiber-optic interferometer
Input port, 2 be output port.
The frequency comb enters in testing fiber interferometer 108 after single-mode optical-fibre coupler 107, the interference to be measured
Instrument 108 will form frequency comb and be divided into two-way optical frequency comb, and two-way frequency comb occurs after the output end combining of interferometer 108 to be measured
Interference in frequency comb, the interference signal just carry the arm length difference information of interferometer to be measured.
The working principle that the measurement method of optical interferometer arm length difference of the invention uses includes as follows：
Measuring principle of the invention is the interference of radiofrequency signal, and frequency comb carries out photoelectricity through high-speed photodetector 109 and turns
It after changing, exports and is combed for radio frequency, therefore frequency comb can be understood as light and carry radio frequency comb, light carries radio frequency comb by testing fiber interferometer
It after 108, will be interfered in microwave domain, the period of the interference signal is determined by 108 two-arm optical path difference of interferometer to be measured, to be measured
The emergent light of fibre optic interferometer 108 is represented by：
I (f)=I0[1+cosφ(f)] (1)
I in above formula0To enter the light intensity for injecting interferometer 108 to be measured, phase of the φ (f) between interferometer two-arm to be measured
Difference is represented by：
D is interferometer two-arm arm length difference to be measured in above formula, and n is the refractive index of optical fiber, and c is the light velocity.Photodetector 109 connects
It receives the interference signal that interferometer 108 to be measured exports and is converted into electric signal, observe the electric signal with frequency spectrograph 201, can obtain
To a cosine microwave signal, the frequency interval Δ f between adjacent two wave crest or trough of the signal is：
The arm length difference of 108 two-arm of interferometer to be measured is represented by：
From the above equation, we can see that according to light velocity constant c, the letter in a cycle that the refractive index n and frequency spectrograph 201 of optical fiber are obtained
Number frequency range Δ f, so that it may obtain the arm length difference of interferometer two-arm to be measured.
If two-arm arm length difference is 5mm, pass through between adjacent two wave crest of microwave signal that photodetector 109 exports
Frequency interval is 30GHz, if two-arm arm length difference is 5m, adjacent two wave of microwave signal exported by photodetector 109
Frequency interval between peak is 300MHz.Therefore this method is particularly well suited to measure the interferometer of big arm length difference, compensates for utilization
The method of optical interference cannot achieve the shortcomings that big brachium difference measurements.When d is constant, the modulating frequency for reducing phase-modulator can
To reduce the repetition rate of frequency comb, make rf frequency smaller interval in frequency comb, thus the week for obtaining frequency spectrograph 201
Significant figure strong point in phase is more, and the precision of measurement result can be improved.
The workflow of fibre optic interferometer arm length difference measuring system proposed by the present invention is simple, and testing fiber interferometer is connect
Enter into measuring system, after system electrification, records the frequency interval Δ f in frequency spectrograph output signal a cycle2, according to formula
(4) it can be obtained by result to be measured.
Although the illustrative specific embodiment of the present invention is described above, in order to the technology of the art
Personnel are it will be appreciated that the present invention, but the present invention is not limited only to the range of specific embodiment, to the common skill of the art
For art personnel, as long as long as various change the attached claims limit and determine spirit and scope of the invention in, one
The innovation and creation using present inventive concept are cut in the column of protection.
Claims (1)
1. a kind of measurement method based on optical interferometer arm length difference measuring system, which is characterized in that measuring system is by changing light
The frequency interval of frequency comb realizes the variation of measurement accuracy, and this method comprises the following steps：
Its measuring principle is the interference of radiofrequency signal, and the frequency comb is defeated after high-speed photodetector 109 carries out photoelectric conversion
It is combed out for radio frequency, therefore frequency comb, it will be appreciated that carrying radio frequency comb for light, light carries radio frequency comb after testing fiber interferometer 108,
It will be interfered in microwave domain, the period of the interference signal is determined by 108 two-arm optical path difference of interferometer to be measured, and testing fiber is dry
The emergent light of interferometer 108 is represented by：
I (f)=I0[1+cosφ(f)] (1)
I in above formula0To enter the light intensity for injecting interferometer 108 to be measured, phase difference of the φ (f) between interferometer two-arm to be measured is indicated
For：
D is interferometer two-arm arm length difference to be measured in above formula, and n is the refractive index of optical fiber, and c is the light velocity, and photodetector 109 receives
The interference signal of the output of interferometer 108 to be measured is simultaneously converted into electric signal, observes the electric signal with frequency spectrograph 201, obtains a cosine
Microwave signal, the frequency interval Δ f between adjacent two wave crest or trough of the signal are：
The arm length difference of 108 two-arm of interferometer to be measured is represented by：
From the above equation, we can see that the signal frequency according to light velocity constant c, in a cycle that the refractive index n and frequency spectrograph 201 of optical fiber are obtained
Rate range delta f obtains the arm length difference of interferometer two-arm to be measured by formula (4).
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Cited By (5)
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| CN110186500A (en) * | 2018-12-25 | 2019-08-30 | 中国船舶重工集团公司第七一五研究所 | A kind of non-equilibrium fibre optic interferometer arm length difference measuring device and measuring method using absolute method |
| CN110608761A (en) * | 2019-10-30 | 2019-12-24 | 珠海任驰光电科技有限公司 | Optical fiber interference device and method capable of eliminating associated amplitude modulation |
| CN111551198A (en) * | 2020-04-22 | 2020-08-18 | 中国科学院上海光学精密机械研究所 | Optical fiber interferometer arm length difference testing system and testing method |
| CN111693133A (en) * | 2020-06-24 | 2020-09-22 | 中国电子产品可靠性与环境试验研究所（（工业和信息化部电子第五研究所）（中国赛宝实验室）） | Optical path difference testing device and method for optical fiber hydrophone and computer equipment |
| CN112129491A (en) * | 2020-10-23 | 2020-12-25 | 南京航空航天大学 | Optical fiber time delay measuring method and device based on single-optical-frequency comb interference |
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2018
- 2018-06-01 CN CN201810560911.8A patent/CN108844717A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110186500A (en) * | 2018-12-25 | 2019-08-30 | 中国船舶重工集团公司第七一五研究所 | A kind of non-equilibrium fibre optic interferometer arm length difference measuring device and measuring method using absolute method |
| CN110186500B (en) * | 2018-12-25 | 2021-04-27 | 中国船舶重工集团公司第七一五研究所 | Unbalanced optical fiber interferometer arm length difference measuring device and method adopting absolute method |
| CN110608761A (en) * | 2019-10-30 | 2019-12-24 | 珠海任驰光电科技有限公司 | Optical fiber interference device and method capable of eliminating associated amplitude modulation |
| CN110608761B (en) * | 2019-10-30 | 2024-05-14 | 珠海任驰光电科技有限公司 | Optical fiber interference device and method capable of eliminating associated amplitude modulation |
| CN111551198A (en) * | 2020-04-22 | 2020-08-18 | 中国科学院上海光学精密机械研究所 | Optical fiber interferometer arm length difference testing system and testing method |
| CN111693133A (en) * | 2020-06-24 | 2020-09-22 | 中国电子产品可靠性与环境试验研究所（（工业和信息化部电子第五研究所）（中国赛宝实验室）） | Optical path difference testing device and method for optical fiber hydrophone and computer equipment |
| CN112129491A (en) * | 2020-10-23 | 2020-12-25 | 南京航空航天大学 | Optical fiber time delay measuring method and device based on single-optical-frequency comb interference |
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