CN104406682A - Interference signal correlation adjusting method of dual Mach-Zehnder optical fiber interference system - Google Patents
Interference signal correlation adjusting method of dual Mach-Zehnder optical fiber interference system Download PDFInfo
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Abstract
The invention provides an interference signal correlation adjusting method of a dual Mach-Zehnder optical fiber interference system. A photoelastic effect is generated by utilizing extrusion stress generated by piezoelectric ceramics. Two paths of interference optical signals are utilized to act as feedback, and the polarization state of the two paths of the interference signals is adjusted to be consistent. With application of the aforementioned scheme, polarization state feedback control is performed on light of a reference arm so that a problem of low signal correlation coefficient induced by inconsistent polarization characteristics in the long-distance dual Mach-Zehnder optical fiber interference system is solved, the detected two paths of the interference signals can be maintained in great correlation, and position information of vibration points can be correctly reflected by time delay of the two paths of the interference signals.
Description
Technical field
The invention belongs to interference signal correlativity regulation technology field, in particular the interference signal correlativity control method of a kind of pair of Mach-Zehnder fiber optic interferometric system.
Background technology
Two-way Mach-Zehnder fiber interference principle as shown in Figure 1, system is made up of distributed feedback semiconductor laser (DFB-LD) 10, optoisolator 11, fiber coupler and photodetector 12 and photodetector 13, wherein three fiber arms comprise pickup arm 14, reference arm 15, time delay arm 16 length can reach 50km, all the other fiber lengths very short (about 1m), negligible when location Calculation.
This fiber-optic vibration test macro course of work is: the narrow-linewidth laser that Distributed Feedback Laser 10 sends enters three-dB coupler C1.Two-way light is separated by coupling mechanism C1, wherein a road enters the M-Z interference system be made up of coupling mechanism C2 and coupling mechanism C3 and transmits along clockwise direction after isolator 11, output to detector PD213 by coupling mechanism C4 to detect, wherein the effect of isolator 11 interferes to prevent two-way light that is clockwise, counterclockwise transmission from forming Sagnac; An other road light transmits the M-Z interference system 17 entering and be made up of coupling mechanism C3 and coupling mechanism C2 in the counterclockwise direction through coupling mechanism C4, and outputs to detector PD112 by coupling mechanism C2 and detect.When without external disturbance effect, two detectors export only has DC component; When applying external disturbance to sensor fibre, two detectors all may detect the light-intensity variation caused by phase place changes, thus realize the waveform that vibration signal can be detected.
When the R place in sensor fibre is disturbed, we set vibration signal to be transferred to the PD1 time used as t along counterclockwise (CCW direction)
1; If vibration signal is t along (CW direction) is transferred to the PD2 time used clockwise
2.Then the transmission optical path distance in CCW direction is X (because sensor fibre length is far longer than the distance of coupling mechanism C2 to detector PD1, therefore can ignore output terminal distance); And the transmission optical path distance in CW direction is L
1+ L
2-X; Then can obtain:
Wherein n is optical fibre refractivity, and c is light speed in a vacuum, and Δ t is the two ways of optical signals time delay that detector detects.For the place of having set up optical cable, L
1, L
2be fixing, as long as the time delay Δ t between two-way vibration signal therefore can be measured, just can orient the position in oscillation point.
This requires the time delay Δ t between two-way vibration signal, and not by the impact of phase place change, and two-way interference signal keeps good correlativity.
In the two Mach-Zehnder fiber optic interferometric system of long distance, the intensity (light intensity) of two-way interference signal is relevant with the phase place of two paths of signals with oscillation intensity.Phase place on the impact of oscillation intensity as shown in Figure 2, two-route wire polarized light (vibration phase A, vibration phase B) its phase 180 degree, when interfering, it interferes the light intensity obtained to be different, the trough of the corresponding vibrational waveform B of crest of vibrational waveform A.In the process realizing location, two-way interferes the light signal polarization state of arm to be random variation, causes the light correlativity of two-way interference signal low.
Therefore, prior art existing defects, needs to improve.
Summary of the invention
Technical matters to be solved by this invention is for the deficiencies in the prior art, provides the interference signal correlativity control method of a kind of pair of Mach-Zehnder fiber optic interferometric system.
Technical scheme of the present invention is as follows:
An interference signal correlativity control method for pair Mach-Zehnder fiber optic interferometric system, wherein, comprising:
Four the piezoelectricity squeezers be made up of piezoelectric ceramics, each action direction become miter angle extrude optical fiber, form Polarization Controller, on the time delay arm that described Polarization Controller is added in light path and be the one end near laser instrument;
By feedback, allow the polarization state entering interference region counterclockwise, be consistent with the polarization state entering interference region clockwise.
Described interference signal correlativity control method, wherein, described Polarization Controller is made up of four direction piezoelectric ceramics, is changed to realize entering interference region polarisation of light state omnirange counterclockwise by the voltage controlling each Polarization Controller the two poles of the earth without dead angle.
Described interference signal correlativity control method, wherein, the deformation quantity of described piezoelectric ceramics is relevant with the voltage being supplied to piezoelectric ceramics the two poles of the earth, changes the deformation quantity of all directions by changing control voltage, and then changes the deformation quantity of piezoelectric ceramics extruding optical fiber.
Described interference signal correlativity control method, wherein, regulates the polarization state entering interference region counterclockwise and regulates consistent with the polarization state entering interference region clockwise, keep good correlativity for the interference signal allowed counterclockwise and produce clockwise.
Described interference signal correlativity control method, wherein, there is the carrier wave of a low frequency in the described interference signal produced counterclockwise and clockwise, when the polarization state of two-way interference light is inconsistent, the voltage difference that two detectors detect is as feedback signal, with full search algorithm, by controlling Polarization Controller input voltage, realizing entering interference region polarisation of light state counterclockwise and clockwise and being consistent.
Employing such scheme has the following advantages:
1, solve the signal coherency existed in the two Mach-Zehnder fiber optic interferometric system of long distance poor, the problem of vibration signal location can not be used for.
2, the polarization state of time delay arm in optical interference circuit is controlled in real time by automatically controlled piezoelectric ceramics, the voltage difference detected using two detectors is as feedback signal, realizing the adjustment of polarization state---implementation method is simple, and control circuit, software algorithm are simple, and easily realizes automatically regulating in real time.
3, adopt general single mode fiber to realize location, solve and adopt polarization maintaining optical fibre high cost problem.
Accompanying drawing explanation
Fig. 1 is two-way M-Z principle of interference figure in prior art.
Fig. 2 is the vibration signal interference effect figure of out of phase in prior art.
Fig. 3 is automatically controlled Polarization Controller structural representation in the embodiment of the present invention.
Fig. 4 is the round complex plane design sketch that in the embodiment of the present invention, Polarization Controller controls polarization state.
Fig. 5 is the light path schematic diagram adding Polarization Controller in the embodiment of the present invention.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.
Embodiment 1
The present invention regulates polarization state to use automatically controlled piezoelectric type Polarization Controller, it is the piezoelectricity squeezer be made up of piezoelectric ceramics, the deformation quantity of piezoelectric ceramics is relevant with the voltage being supplied to piezoelectric ceramics the two poles of the earth, so the deformation quantity of all directions can be changed by changing control voltage, and then change the deformation quantity of piezoelectric ceramics extruding optical fiber.
Automatically controlled piezoelectric type Polarization Controller is: the photoelastic effect produced when utilizing piezoelectric ceramics to extrude optical fiber, produces phase delay.The fibre core of desirable single-mode fiber is the circle of rule, the electric field intensity propagation rate in all directions of light is equal, and when applying a pressure to optical fiber, its fibre core has just been approximated to an ellipse, when the birefringence that piezoelectric ceramics produces when extruding optical fiber, phase differential meets:
Wherein f is the power that in unit length, optical fiber is subject to, and d is the diameter of light, constant k=9.5 × 10
-5rad/m, δ are the phase differential produced.The polarization state of respective direction so just can be changed by changing piezoelectric ceramics two pole tension added in all directions.
Automatically controlled piezoelectric type Polarization Controller concrete structure as shown in Figure 3, be made up of the piezoelectricity squeezer of four direction, its each action direction becomes miter angle, when powering on, 4 squeezers extrude optical fiber from four direction: as piezoelectricity squeezer A extrudes optical fiber from vertical direction, piezoelectricity squeezer B is from miter angle direction extruding optical fiber, piezoelectricity squeezer C extrudes optical fiber from vertical direction, and piezoelectricity squeezer D is from miter angle direction extruding optical fiber.
In Fig. 3, piezoelectricity squeezer controls the round complex plane effect of polarization state as shown in Figure 4, and when in Fig. 3,0 degree of angular direction extrudes, polarization state develops along the linear axis of S1 in Fig. 4, and the linear axis along S2 in Fig. 4 during the extruding of miter angle direction in Fig. 3 develops.Such as, in order to polarization state A in Fig. 4 is changed into polarization state C, the piezoelectric ceramics of change 45 degree of deflections (in Fig. 3 B) is needed to extrude voltage, polarization state is made to be evolved into polarization state B, then change the extruding voltage of 0 degree of deflection piezoelectric ceramics (in Fig. 3 A), make polarization state be evolved into polarization state C.As shown in Figure 4, by the extruding in 0 degree and 45 degree direction, any point can arrive in addition a bit by rotating, and adopts four squeezers to be generations in order to prevent dead angle.
For the two Mach-Zehnder fiber optic interferometric system of long distance, because optical fiber link is very long, optical fiber stressed very uneven, the interference light intensity change that the change of polarization state causes is random.Substantially light can not be allowed to transmit in a fiber with ordinary optic fibre and not produce polarization state change, even producing fixing polarization state and change all very difficult.The present invention selects to avoid polarization state in optical fiber to be adjusted to fixing angle for this reason, but by feedback, allows the polarization state ψ 2 entering interference region counterclockwise, is consistent with the polarization state ψ 1 entering interference region clockwise.Due to the symmetry of two M-Z light path, the light signal that two-way detector now obtains is consistent, thus ensures the accuracy of location.
As shown in Figure 5, Polarization Controller 25 is added on the time delay arm 29 of light path light path after improving, (near one end of laser instrument 20, being convenient to realize the control to Polarization Controller 25).The light that laser instrument 20 sends is divided into two-way through coupling mechanism C3, clockwise light is through isolator 23 (preventing from two-way light that is clockwise, counterclockwise transmission from forming Sagnac to interfere), enter interference region 30, if the polarization state entering interference region is ψ 1 number in the figure is 21, anticlockwise light is through coupling mechanism C4, Polarization Controller 25, enters interference region 30, if the light entering interference region is polarization state ψ 2 number in the figure is 26.Anticlockwise optical transport is to interference region 30 link longer (tens kilometers), due to the effect such as temperature stress on the way, polarization state ψ 2 and polarization state ψ 1 have phase differential, this phase differential causes the correlativity of follow-up interference light very poor, by regulating the voltage of Polarization Controller 25, polarization state ψ 2 can be changed, polarization state ψ 2 and polarization state ψ 1 are consistent.Clockwise like this light is divided into two-way in interference region through coupling mechanism C1, (interference signal carries the disturbing signal of interfering on arm to interfere arms and 28 reference arms to interfere at coupling mechanism C2 place through 27 respectively, number in the figure is R), anticlockwise light is divided into two-way in interference region through coupling mechanism C2, (interference signal carries the disturbing signal of interfering on arm to interfere arms and 28 reference arms to interfere at coupling mechanism C1 place through 27 respectively, number in the figure is R), because the suitable backlight polarization state entering interference region is consistent, reversible in the light path of the light process in direction, interference region two, known by the reversibility of light path, at clockwise interference of light point C2 and counterclockwise interference of light point C1, the light phase of arm and pickup arm is interfered to be consistent respectively, such interference signal out can keep very high correlativity.Clockwise light is detected device 2 (number in the figure be 24) at coupling mechanism C4 place through light splitting through pickup arm 29 and detects, and anticlockwise light is detected device 1 (number in the figure is 22) at the C1 place that interference is gone through light splitting and detects.
The algorithm realizing polarization state ψ 2 adjustment is full search algorithm, concrete principle is: due to the beat frequency phenomenon of light wave, when whole interference system does not have vibration signal, two-way interference signal has the carrier wave of a low frequency, when the polarization state of two-way interference light is inconsistent, the carrier wave of this low frequency is also inconsistent.So by the difference of this two paths of signals (i.e. two detectors detect voltage difference) as feedback signal, with full search algorithm, by controlling Polarization Controller input voltage, realizing two and entering interference region polarisation of light state and be consistent.
Through the adjustment of Polarization Controller, the phase place of two paths of signals in optical interference circuit can be made identical, thus the intensity of two-way interference signal (light intensity) is only correlated with oscillation intensity.Because two-way interference signal is after long range propagation, phase place random variation will cause again polarization state inconsistent, and this method monitors voltage difference that two detectors detect in real time as feedback signal, keep two-way to enter interference region polarisation of light state in real time consistent.The light intensity that such detector detects by correlativity good for real-time ensuring, the delay inequality reflecting vibration signal that the delay inequality of light intensity can be good.Calculated the delay inequality of vibration signal by the acquisition system of precision, just can realize the two Mach-Zehnder fiber optic interferometric system of long distance to the positioning function of vibration signal.
Employing such scheme has the following advantages:
1, solve the signal coherency existed in the two Mach-Zehnder fiber optic interferometric system of long distance poor, the problem of vibration signal location can not be used for.
2, the polarization state of time delay arm in optical interference circuit is controlled in real time by automatically controlled piezoelectric ceramics, the voltage difference detected using two detectors is as feedback signal, realizing the adjustment of polarization state---implementation method is simple, and control circuit, software algorithm are simple, and easily realizes automatically regulating in real time.
3, adopt general single mode fiber to realize location, solve and adopt polarization maintaining optical fibre high cost problem.
Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improve and convert the protection domain that all should belong to claims of the present invention.
Claims (5)
1. an interference signal correlativity control method for two Mach-Zehnder fiber optic interferometric system, is characterized in that, comprising:
Four the piezoelectricity squeezers be made up of piezoelectric ceramics, each action direction become miter angle extrude optical fiber, form Polarization Controller, on the time delay arm that described Polarization Controller is added in light path and be the one end near laser instrument;
By feedback, allow the polarization state entering interference region counterclockwise, be consistent with the polarization state entering interference region clockwise.
2. interference signal correlativity control method as claimed in claim 1, it is characterized in that, described Polarization Controller is made up of four direction piezoelectric ceramics, is changed to realize entering interference region polarisation of light state omnirange counterclockwise by the voltage controlling each Polarization Controller the two poles of the earth without dead angle.
3. interference signal correlativity control method as claimed in claim 2, it is characterized in that, the deformation quantity of described piezoelectric ceramics is relevant with the voltage being supplied to piezoelectric ceramics the two poles of the earth, changes the deformation quantity of all directions by changing control voltage, and then changes the deformation quantity of piezoelectric ceramics extruding optical fiber.
4. interference signal correlativity control method as claimed in claim 1, it is characterized in that, being regulated by the polarization state entering interference region counterclockwise regulates consistent with the polarization state entering interference region clockwise, keeps good correlativity for the interference signal allowed counterclockwise and produce clockwise.
5. interference signal correlativity control method as claimed in claim 1, it is characterized in that, there is the carrier wave of a low frequency in the described interference signal produced counterclockwise and clockwise, when the polarization state of two-way interference light is inconsistent, the voltage difference that two detectors detect is as feedback signal, with full search algorithm, by controlling Polarization Controller input voltage, realizing entering interference region polarisation of light state counterclockwise and clockwise and being consistent.
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| CN105300507A (en) * | 2015-10-26 | 2016-02-03 | 南京航空航天大学 | Optical fiber vibration sensor and M-Z sensing arm optical path structure comprising same |
| CN110119039A (en) * | 2018-02-07 | 2019-08-13 | 桂林电子科技大学 | Spiral microarray format modulation type optical fiber vortex field generator |
| CN110119041A (en) * | 2018-02-07 | 2019-08-13 | 桂林电子科技大学 | Piezoelectric ceramics microarray polarization type optical fiber acousto-optic device |
| CN110119043A (en) * | 2018-02-07 | 2019-08-13 | 桂林电子科技大学 | Fiber polarization controller based on cross-polarization type piezoelectric ceramics microarray |
| CN113108710A (en) * | 2021-04-14 | 2021-07-13 | 安徽大学 | Optical low-frequency strain detection system and detection method based on ellipse fitting |
| CN117848483A (en) * | 2024-02-26 | 2024-04-09 | 广州杰鑫科技股份有限公司 | Optical fiber vibration sensing system, optical fiber vibration sensing method and optical cable line inspection analyzer |
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| CN101526374A (en) * | 2009-02-13 | 2009-09-09 | 上海大学 | Full optical-fiber Mach-Zehnder interferometer of polarization fading and polarization phase-position noise resistance |
| CN102291181A (en) * | 2011-08-09 | 2011-12-21 | 天津大学 | Polarization control method and system of distributed optical fiber disturbance positioning system |
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Patent Citations (3)
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| CN101344452A (en) * | 2008-08-22 | 2009-01-14 | 北京交通大学 | Method and device for implementing polarization sensitive optical time domain reflection technology by using piezoelectric ceramic |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105300507A (en) * | 2015-10-26 | 2016-02-03 | 南京航空航天大学 | Optical fiber vibration sensor and M-Z sensing arm optical path structure comprising same |
| CN105300507B (en) * | 2015-10-26 | 2018-08-28 | 南京航空航天大学 | Optical fibre vibration sensor and its M-Z pickup arm light channel structures |
| CN110119039A (en) * | 2018-02-07 | 2019-08-13 | 桂林电子科技大学 | Spiral microarray format modulation type optical fiber vortex field generator |
| CN110119041A (en) * | 2018-02-07 | 2019-08-13 | 桂林电子科技大学 | Piezoelectric ceramics microarray polarization type optical fiber acousto-optic device |
| CN110119043A (en) * | 2018-02-07 | 2019-08-13 | 桂林电子科技大学 | Fiber polarization controller based on cross-polarization type piezoelectric ceramics microarray |
| CN113108710A (en) * | 2021-04-14 | 2021-07-13 | 安徽大学 | Optical low-frequency strain detection system and detection method based on ellipse fitting |
| CN117848483A (en) * | 2024-02-26 | 2024-04-09 | 广州杰鑫科技股份有限公司 | Optical fiber vibration sensing system, optical fiber vibration sensing method and optical cable line inspection analyzer |
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