CN102980601A - Demodulating device and method for optical fiber Young interference optical path difference based on low coherent interference - Google Patents

Abstract

The invention discloses a demodulating device for an optical fiber Young interference optical path difference based on low coherent interference. The demodulating device comprises a wideband light source, a 3dB coupler, a sensing interferometer, a demodulating interferometer, a calibration interferometer and a line array camera, wherein a multimode optical fiber is adopted in a light path formed by the components in sequence for optical signal transmission. A demodulating method mainly comprises the steps of optical path difference sensing, optical path difference demodulating and optical path difference calibration. Compared with the prior art, the demodulating device and the method integrate modes of space scanning and time scanning to conduct low coherent interference optical path difference demodulating; no mechanical movement is available; the stability is high; compared with the time scanning, the demodulating precision is not affected by moving precision of a scanning motor; the nano-level high precision demodulating can be realized; the optical path difference calibration of an overall system is realized by adjusting the optical path difference; in addition, a nano displacement platform is adopted to control the output optical path difference effectively; an optical path difference demodulating interval of the overall system is amended; and with the adoption of an optical fiber interferometer structural form, the system adjustment is facilitated and the working stability is high.

Description

Optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment and method based on low coherence interference

Technical field

The present invention relates in sensory field of optic fibre, particularly relate to a kind of optical path difference demodulation method and device.

Background technology

The low coherence interference technology is used for its principle of optical path difference demodulation and is, utilize demodulated interferential instrument optical path difference and sensing interferometer optical path difference to carry out scan matching, under the condition of the strict coupling of both optical path differences, export the strongest low coherence interference signal, realize at last the high precision demodulation of optical path difference to be measured by the mode of accurate location low coherence interference signal envelope peak value.

The low coherence interference technology mainly contains time scan formula and spacescan formula as the optical path difference demodulation method.The time scan formula is the scanning of optical path difference temporal evolution.Such as (Parallel demodulation system andsignal-processing method for extrinsic Fabry-Perot interferometer and fiber Bragg gratingsensors such as Junfeng Jiang, Optics Letters, 2005,30:604-606) the wherein movement of an arm by Electric Machine Control Michelson interferometer, carry out optical path scanning, thereby match optical path difference to be measured.The spacescan formula is that optical path difference is linear distribution along the locus, utilizes line-scan digital camera to receive the spacescan of realizing optical path difference.Such as J.Schwider(White-lightFizeau interferometer, Applied Optics, 1997,36:1433-1437) Fizeau white light interferometer structure was proposed in 1997, the wedge that utilizes the Fizeau interferometer to consist of is realized the optical path difference space distribution.(the Marshall such as Marshall, R., et al., A novel electronically scanned white-light interferometer using aMach-Zehnder approach.Lightwave Technology, Journal of, 1996.14 (3): 397-402) proposed to adopt the Mach-Zehnder interferometer structure to realize the space distribution of optical path difference in 1996.

Although time scan formula measurement range is large, there is mechanical motion in system, if long-term stability in use and measuring accuracy are affected by it all, measuring accuracy is relatively low can only be in micron dimension.The motion of spacescan formula machinery-free, long-term stability in use is high, and its demodulation accuracy is affected by line-scan digital camera pixel number mainly, and measuring accuracy can reach nanometer scale.But spatial light path difference sweep limit is limited by system architecture, and measurement range is little.

Summary of the invention

For overcoming the deficiencies in the prior art, the present invention proposes a kind of optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment and method based on low coherence interference, carry out the demodulation of low coherence interference optical path difference in conjunction with spacescan mode and time scan mode, optical path difference demodulation method of the present invention can be used for also realizing that displacement, pressure, strain, temperature, refractive index etc. can be converted into high-precision sensing and the demodulation of the physical quantity of optical path difference variation.

The present invention proposes a kind of optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment based on low coherence interference, this demodulating equipment comprises wideband light source, three-dB coupler, sensing interferometer, demodulated interferential instrument, proofreaies and correct interferometer and line-scan digital camera, adopt multimode optical fiber to carry out optical signal transmission between the light path that each parts sequentially forms, it is characterized in that, described sensing interferometer adopts Michelson interferometer, and the demodulated interferential instrument adopts the optical fiber Young's interferometer and proofreaies and correct interferometer and adopt the adjustable Mach Zehnder interferometer of optical path difference:

The light that wideband light source sends is divided into two-way light by 2 * 2 three-dB couplers, two-way light passed through respectively arm of Michelson interferometer and No. two arms, and after being reflected by arm reflection end face of Michelson interferometer and No. two arm reflection end faces respectively, again by the synthetic light beam of 2 * 2 three-dB couplers, and be transferred to 2 * 1 three-dB couplers, 2 * 13dB coupling mechanism is divided into two-way with light again, is respectively arm of Mach Zehnder interferometer and No. two arms; The optical path difference means for correcting that is present on arm of Mach Zehnder interferometer comprises the first GRIN Lens, the second GRIN Lens, nanometer displacement platform: by the Space Collimation light beam of the first GRIN Lens output, in air, propagate after the segment distance, get back among the multimode optical fiber by the second GRIN Lens, mobile nanometer displacement platform changes the aerial propagation distance of Space Collimation light beam, thereby regulates the Mach Zehnder interferometer optical path difference; Mach Zehnder interferometer two arm optical fiber connectors are fixed by fiber array side by side, consist of the optical fiber Young's interferometer; Fiber end face overlaps with the cylindrical mirror focal plane of fiber array back, and the light that is light belt by the cylindrical mirror compression is received by line-scan digital camera, and the optical path difference on the line-scan digital camera receiving plane is linear distribution, realizes optical path difference space linear sweep.

Described demodulated interferential instrument adopts the optical fiber Fabry-Perot interferometer:, form with reference to reflected light at optical fiber Fabry-Perot interferometer fiber end face generating unit sub reflector along the light of Optical Fiber Transmission; Transmitted light by with fiber end face distance, delta L ₂Mirror reflects after again be coupled to optical fiber, form sensory reflex light, behind reflected light and sensory reflex light compositing light beam, comprised 2 Δ L ₂Optical path difference information, change catoptron apart from the distance of fiber end face, namely changed optical path difference sensing amount.

According to the sensitization requirement of line-scan digital camera, described wideband light source is selected white LED light source, Halogen lamp LED, xenon lamp or ASE light source.

Described three-dB coupler is selected multi-module optical fiber coupler, and described line-scan digital camera is selected linear array CCD camera.In addition, according to selecting the light source spectral band, select other line-scan digital cameras, linear array CMOS is arranged, linear array Gallium indium arsenide photodetector.

The invention allows for a kind of optical fiber Mechanical Study On Young Interference optical path difference demodulation method based on low coherence interference, it is characterized in that the method may further comprise the steps:

Step 1, the light that wideband light source is sent is divided into two-way light by 2 * 2 three-dB couplers, pass through respectively arm of Michelson interferometer and No. two arms, after two-way light is reflected by arm reflection end face of Michelson interferometer and No. two arm reflection end faces respectively, again by the synthetic light beam of 2 * 2 three-dB couplers; Optical path difference information 2 Δ L will be had in the reflected light ₁Be transferred to 2 * 1 three-dB couplers, realize the optical path difference sensing;

Step 2 is divided into two-way with the reflected light in the step 1 by 2 * 1 three-dB coupler light, passes through respectively arm of Mach Zehnder interferometer and No. two arms and obtains light path corresponding to two arms; Carry out following operation by being present in the optical path difference means for correcting that is comprised of the first GRIN Lens, the second GRIN Lens, nanometer displacement platform on arm of Mach Zehnder interferometer: the Space Collimation light beam of the first GRIN Lens output is propagated in air after the segment distance, get back among the multimode optical fiber by the second GRIN Lens, mobile nanometer displacement platform changes the aerial propagation distance of Space Collimation light beam, thereby regulates arm light path of Mach Zehnder interferometer; Through aforementioned operation, output optical signal and optical path difference information thereof;

Step 3, the optical fiber connector of arm of Mach Zehnder interferometer and No. two arms is fixed by fiber array side by side, consist of Young's interferometer: the Mach Zehnder interferometer fiber end face overlaps with the cylindrical mirror focal plane of fiber array back; The light that is light belt by the cylindrical mirror compression is received by line-scan digital camera; Two optical fiber connector spacings are d, and the distance of fiber end face range line array camera is D, and two-beam outputs to and produces final interference fringe on the light overlapping region of line-scan digital camera, and is received by line-scan digital camera; Be far smaller than under the D condition at d, optical path difference is linear distribution in the light overlapping region, satisfies formula:

Δ＝xd/D，

Wherein x represents corresponding line-scan digital camera position;

Step 4 is carried out the interference light path difference and is proofreaied and correct, and optical path difference is expressed as: Δ '=2 Δ L ₁-(l ₁-l ₂)-xd/D, l ₁, l ₂Represent respectively arm of Mach Zehnder interferometer and No. two arms;

When Δ '=0, corresponding x position, output low coherence interference signal envelope peak value; After the adjustment of correction interferometer is finished, l ₁-l ₂Be constant, x is with Δ L ₁And change, and have one-to-one relationship, by accurate location x value, can realize the high precision demodulation of optical path difference to be measured.

Described step 4 also comprises: regulate between arm of Mach Zehnder interferometer and No. two arm two brachiums apart from l ₁-l ₂, realize the interval demodulation of different optical path differences.

Described step 1 adopts the optical fiber Fabry-Perot interferometer to realize the optical path difference sensing, and its interference light path difference sensing flow process comprises following operation:

The light that wideband light source is sent is by 2 * 2 three-dB couplers,, forms with reference to reflected light at fiber end face generating unit sub reflector along the light of Optical Fiber Transmission; Transmitted light by with fiber end face distance, delta L ₂Mirror reflects after again be coupled to optical fiber, form sensory reflex light, behind reflected light and sensory reflex light compositing light beam, comprised 2 Δ L ₂Optical path difference information, change catoptron apart from the distance of fiber end face, namely changed optical path difference sensing amount.

Compared with prior art, the present invention's mode of combining spacescan and time scan is carried out the demodulation of low coherence interference optical path difference:

1, in demodulated interferential instrument part, adopt Mechanical Study On Young Interference to form the space linear distribution scanning of optical path difference, line-scan digital camera directly receives the low coherence interference striped of exporting behind the optical path scanning, the machinery-free motion, stability is high.Than time scan, this Demodulation Systems precision is not affected by the scan module mobile accuracy, and the selective system parameter realizes the high precision demodulation of nanometer scale;

2, proofread and correct the interferometer part, by regulating the wherein optical path difference of an arm of Mach Zehnder interferometer, realizing the purpose that the whole system optical path difference is proofreaied and correct.Effectively control the output optical path difference of Mach Zehnder interferometer by high-precision nanometer displacement platform, in the whole system that is added to, the optical path difference demodulation of revising whole system is interval;

3, adopt the fibre optic interferometer structural shape, system is easy to adjust, and job stability is high.

Description of drawings

Fig. 1 is based on the optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment figure of low coherence interference;

Fig. 2 is Michelson sensing interferometer two arm optical path difference synoptic diagram;

Fig. 3 is Fa-Po sensing interferometer two arm optical path difference synoptic diagram;

Fig. 4 is Young demodulated interferential instrument optical path difference space distribution scanning demodulation synoptic diagram;

Fig. 5 is the low coherence interference striped normalization simulation light intensity curve of system's output;

Fig. 6 is that Mach Zehnder is proofreaied and correct interferometer two arm optical path differences correction synoptic diagram;

Fig. 7 is system's optical path scanning scope and sweep interval correction analysis synoptic diagram.

Among the figure, 1, wideband light source, 2,2 * 2 three-dB couplers, 3, No. 1 arm of Michelson interferometer, 4, an arm reflection of Michelson interferometer end face, 5, No. two arms of Michelson interferometer, 6, No. 2 arm reflections of Michelson interferometer end face, 7,2 * 1 three-dB couplers, 8, arm of Mach Zehnder interferometer, 9, No. two arms of Mach Zehnder interferometer, 10, the first GRIN Lens, 11, the second GRIN Lens, 12, the Space Collimation light beam, 13, the nanometer displacement platform, 14, fiber array, 15, line-scan digital camera, 16, the light overlapping region, 17, fiber end face (first reflecting surface of Fabry-Perot Interferometer), 18, reflection end face (second reflecting surface of Fabry-Perot Interferometer), 19, Fabry-Perot Interferometer the first folded light beam, 20, Fabry-Perot Interferometer the second folded light beam.21, line-scan digital camera position, 22, Mach Zehnder interferometer optical path difference, 23, Young's interferometer optical path difference, 24, system scan optical path difference, 25, Mach Zehnder interferometer optical path difference distribution curve, 26, Young's interferometer optical path difference distribution curve, 27, demodulation low coherence interference striped simulation light intensity curve corresponding to first optical path difference, 28, demodulation low coherence interference striped simulation light intensity curve corresponding to second optical path difference, 29, cylindrical mirror.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in detail, if there is exemplary content in these embodiments, should not be construed to limitation of the present invention.

Embodiment 1: based on the optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment of low coherence interference

This system's ingredient comprises wideband light source, three-dB coupler, and sensing interferometer, the demodulated interferential instrument is proofreaied and correct interferometer and line-scan digital camera six large parts, adopts multimode optical fiber to carry out optical signal transmission between each parts.

As shown in Figure 1, the light that wideband light source 1 sends is divided into two-way light by 2 * 2 three-dB couplers 2, two-way light passes through respectively No. 1 arm 3 of Michelson interferometer and No. 2 arms 5, after being reflected by No. 1 arm reflection end face 4 of Michelson interferometer and No. 2 arm reflection end faces 6 respectively, again synthesize light beams by 2 * 2 three-dB couplers 2, and be transferred to 2 * 1 three-dB couplers 7; 2 * 1 three-dB couplers 7 are divided into two-way with light again, pass through respectively arm 8 of Mach Zehnder interferometer and No. two arms 9, the optical path difference means for correcting that is arranged on No. 1 arm 8 of Mach Zehnder interferometer comprises the first GRIN Lens 10, the second GRIN Lens 11, nanometer displacement platform 13.Space Collimation light beam 12 by 10 outputs of the first GRIN Lens, in air, propagate after the segment distance, get back among the multimode optical fiber by the second GRIN Lens 11, mobile nanometer displacement platform 13 changes Space Collimation light beam 12 aerial propagation distances, thereby regulates the Mach Zehnder interferometer optical path difference.The optical fiber connector of this two arm side by side, and is fixing by fiber array 14, consists of the optical fiber Young's interferometer.Fiber end face overlaps with cylindrical mirror 29 focal planes of fiber array 14 back, and the light that is light belt by cylindrical mirror 29 compressions is received by line-scan digital camera 15, and the optical path difference on line-scan digital camera 15 receiving planes is linear distribution, realizes optical path difference space linear sweep.

Element in the above-mentioned demodulating equipment is specially:

Wideband light source according to the sensitization requirement of line-scan digital camera, is selected white LED light source, Halogen lamp LED, xenon lamp, ASE light source;

Three-dB coupler is selected multi-module optical fiber coupler, plays divided beams and the effect of closing light beam;

Sensing interferometer produces optical path difference to be measured, selects Michelson interferometer and Fabry-Perot Interferometer all can as sensing interferometer;

The demodulated interferential instrument adopts the optical fiber Young's interferometer, utilizes its optical path difference spatial characteristics, scan matching optical path difference to be measured.Cylindrical mirror is placed in its optical fiber output rear end, and fiber end face is positioned at cylindrical mirror focus place, and the cylindrical mirror effect is the optical pressure contracting is a light belt, improves the back end of line array camera to the light signal receiving efficiency;

Proofread and correct interferometer: adopt the adjustable Mach Zehnder interferometer of optical path difference, regulate and the demodulated interferential instrument optical path difference distribution sweep limit of proofreading and correct the rear end, make it cover the variation range of optical path difference to be measured fully;

Line-scan digital camera: select linear array CCD camera.In addition, according to selecting the light source spectral band, select other line-scan digital cameras, linear array CMOS is arranged, linear array Gallium indium arsenide photodetector is selective.

Embodiment 2: based on the optical fiber Mechanical Study On Young Interference optical path difference method for sensing of low coherence interference

Based on the optical path difference method for sensing of Optical Fiber Michelson Interferometer as shown in Figure 2,2 * 2 three-dB couplers 2 are divided into two-way with light, be input to respectively arm 3 of Michelson interferometer and No. two arms 5, and after two arm end faces reflect respectively, again synthesize light beam, at this moment, because the difference of two brachiums and so that comprised 2 Δ L in the light signal ₁Optical path difference information, change the wherein length of one arm, namely change optical path difference sensing amount.Except adopting Optical Fiber Michelson Interferometer, the optical fiber Fabry-Perot interferometer is applicable equally, as shown in Figure 3:, form with reference to reflected light 19 at fiber end face 17 generating unit sub reflectors along the light of Optical Fiber Transmission.Transmitted light is coupled to optical fiber after reflecting by the catoptron 18 with fiber end face 17 distance, delta L2 again, form sensory reflex light 20, behind reflected light 19 and sensory reflex light 20 synthetic light beams, the optical path difference information that has comprised 2 Δ L2, change catoptron 18 apart from the distance of fiber end face 17, namely changed optical path difference sensing amount.The method is applicable to be converted into the sensing of any physical quantity that optical path difference changes, such as displacement, pressure, temperature, refractive index etc.

Embodiment 3: based on the optical fiber Mechanical Study On Young Interference optical path difference demodulation method of low coherence interference

As shown in Figure 4, optical fiber Young's interferometer two optical fiber connector spacings are d, and the distance of fiber end face range line array camera is D, and two-beam outputs to and produces final interference fringe on the light overlapping region 16 of line-scan digital camera 15, and are received by line-scan digital camera 15.Be far smaller than under the D condition at d, optical path difference is linear distribution in light overlapping region 16, satisfies formula: Δ=xd/D, wherein x represents the position.Then demodulation low coherence interference striped normalization light intensity can be expressed as:

$I(\mathrm{\λ},x)={\∫}_{-\∞}^{+\∞}S\left(\mathrm{\λ}\right)\·[1-\cos \left(\frac{2\mathrm{\πxd}/D}{\mathrm{\λ}}\right)]\·[1-\cos \left(\frac{4\mathrm{\π}{\mathrm{\ΔL}}_1}{\mathrm{\λ}}\right)]\mathrm{d\λ}---\left(1\right)$

In the following formula: λ represents wavelength, and x represents corresponding line-scan digital camera position, and d represents the optical fiber spacing, and D represents fiber end face and line-scan digital camera distance, Δ L ₁Represent to be measured, S (λ) expression light source light spectrum function.

The spectrum of supposing light source is Gaussian function, then the low coherence interference striped normalization light intensity curve of following formula (1) output as shown in Figure 5, wherein horizontal ordinate represents line-scan digital camera 15 position x, curve 27,28 represents respectively two demodulation low coherence interference striped light intensity curves that different optical path differences are corresponding, and low coherence interference fringe envelope peak corresponds respectively to line-scan digital camera 15 position x1, x2.X is with Δ L ₁And change, and have one-to-one relationship, by accurate location x value, can realize the high precision demodulation of optical path difference to be measured.

Embodiment 4: based on the optical fiber Mechanical Study On Young Interference optical path difference bearing calibration of low coherence interference

System adopts the optical fiber mach Zehnder interferometer to realize the optical path difference correction, and as shown in Figure 6, arm 8 of Mach Zehnder interferometer and No. two arms 9 have respectively corresponding light path.Being present in the optical path difference means for correcting on the arm 8 is comprised of number one GRIN Lens 10, the second GRIN Lens 11, nanometer displacement platform 13.The specific practice of optical path difference bearing calibration is: by the Space Collimation light beam of the first GRIN Lens 10 outputs, in air, propagate after the segment distance, get back among the multimode optical fiber by the second GRIN Lens 11, mobile nanometer displacement platform 13 changes Space Collimation light beam 12 aerial propagation distances, thereby regulates No. 1 arm light path of Mach Zehnder interferometer.Light is by behind the Mach Zehnder interferometer, and output optical signal has increased the optical path difference information of Mach Zehnder interferometer two arm light paths again.The optical path difference of whole system can be expressed as:

Δ′＝2ΔL ₁-(l ₁-l ₂)-xd/D (2)

When Δ '=0, have:

2ΔL ₁＝(l ₁-l ₂)-xd/D (3)

At this moment, corresponding x position, output low coherence interference signal envelope peak value.X by 0 to x ₀Change, the optical path scanning scope of correspondence system is (l ₁-l ₂) to (l ₁-l ₂)-x ₀D/D.System's optical path scanning scope and sweep interval correction analysis as shown in Figure 7, Young's interferometer carries out optical path scanning, Mach Zehnder interferometer is introduced the optical path difference biasing, the bias lighting path difference (l that produces by the control Mach Zehnder interferometer ₁-l ₂), realize the interval scanning of different optical path differences.In addition, by effective control optical path difference amount of bias, so that each amount of bias is scanning maximum optical path difference integral multiple, i.e. (l ₁-l ₂)=nx ₀D/D can make different optical path scannings interval end to end, realizes the purpose of optical path scanning scope expansion.

Claims (7)

1. optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment based on low coherence interference, this demodulating equipment comprises wideband light source, three-dB coupler, sensing interferometer, demodulated interferential instrument, proofreaies and correct interferometer and line-scan digital camera, adopt multimode optical fiber to carry out optical signal transmission between the light path that each parts sequentially forms, it is characterized in that, described sensing interferometer adopts Michelson interferometer, described demodulated interferential instrument adopts the optical fiber Young's interferometer, and described correction interferometer adopts the adjustable Mach Zehnder interferometer of optical path difference:

The light that wideband light source sends is divided into two-way light by 2 * 23dB coupling mechanism, two-way light is respectively by arm of Michelson interferometer and No. two arms, and after being reflected by arm reflection end face of Michelson interferometer and No. two arm reflection end faces respectively, again by the synthetic light beam of 2 * 23dB coupling mechanism, and be transferred to 2 * 13dB coupling mechanism, 2 * 13dB coupling mechanism is divided into two-way with light again, is respectively arm of Mach Zehnder interferometer and No. two arms; The optical path difference means for correcting that is present on arm of Mach Zehnder interferometer comprises the first GRIN Lens, the second GRIN Lens, nanometer displacement platform: by the Space Collimation light beam of the first GRIN Lens output, in air, propagate after the segment distance, get back among the multimode optical fiber by the second GRIN Lens, mobile nanometer displacement platform changes the aerial propagation distance of Space Collimation light beam, thereby regulates the Mach Zehnder interferometer optical path difference; Mach Zehnder interferometer two arm optical fiber connectors are fixed by fiber array side by side, consist of the optical fiber Young's interferometer; Fiber end face overlaps with the cylindrical mirror focal plane of fiber array back, and the light that is light belt by the cylindrical mirror compression is received by line-scan digital camera, and the optical path difference on the line-scan digital camera receiving plane is linear distribution, realizes optical path difference space linear sweep.

2. the optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment based on low coherence interference as claimed in claim 1, it is characterized in that, described sensing interferometer adopts the optical fiber Fabry-Perot interferometer:, form with reference to reflected light at optical fiber Fabry-Perot interferometer fiber end face generating unit sub reflector along the light of Optical Fiber Transmission; Transmitted light by with fiber end face distance, delta L ₂Mirror reflects after again be coupled to optical fiber, form sensory reflex light, behind reflected light and sensory reflex light compositing light beam, comprised 2 Δ L ₂Optical path difference information, change catoptron apart from the distance of fiber end face, namely changed optical path difference sensing amount.

3. the optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment based on low coherence interference as claimed in claim 1 or 2 is characterized in that, according to the sensitization requirement of line-scan digital camera, described wideband light source is selected white LED light source, Halogen lamp LED, xenon lamp or ASE light source.

4. the optical fiber Mechanical Study On Young Interference optical path difference demodulating equipment based on low coherence interference as claimed in claim 1 or 2 is characterized in that, described three-dB coupler is selected multi-module optical fiber coupler, and described line-scan digital camera is selected linear array CCD camera.In addition, according to selecting the light source spectral band, select other line-scan digital cameras, linear array CMOS is arranged, linear array Gallium indium arsenide photodetector.

5. optical fiber Mechanical Study On Young Interference optical path difference demodulation method based on low coherence interference is characterized in that the method may further comprise the steps:

Step 1, the light that wideband light source is sent is divided into two-way light by 2 * 2 three-dB couplers, pass through respectively arm of Michelson interferometer and No. two arms, after two-way light is reflected by arm reflection end face of Michelson interferometer and No. two arm reflection end faces respectively, again by the synthetic light beam of 2 * 2 three-dB couplers; Optical path difference information 2 Δ L will be had in the reflected light ₁Be transferred to 2 * 1 three-dB couplers, realize the optical path difference sensing;

Step 2 is divided into two-way with the reflected light in the step 1 by 2 * 1 three-dB coupler light, passes through respectively arm of Mach Zehnder interferometer and No. two arms and obtains light path corresponding to two arms; Carry out following operation by being present in the optical path difference means for correcting that is comprised of the first GRIN Lens, the second GRIN Lens, nanometer displacement platform on arm of Mach Zehnder interferometer: the Space Collimation light beam of the first GRIN Lens output is propagated in air after the segment distance, get back among the multimode optical fiber by the second GRIN Lens, mobile nanometer displacement platform changes the aerial propagation distance of Space Collimation light beam, thereby regulates arm light path of Mach Zehnder interferometer; Through aforementioned operation, output optical signal and optical path difference information thereof;

Step 3, the optical fiber connector of arm of Mach Zehnder interferometer and No. two arms is fixed by fiber array side by side, consist of Young's interferometer: the Mach Zehnder interferometer fiber end face overlaps with the cylindrical mirror focal plane of fiber array back; The light that is light belt by the cylindrical mirror compression is received by line-scan digital camera; Two optical fiber connector spacings are d, and the distance of fiber end face range line array camera is D, and two-beam outputs to and produces final interference fringe on the light overlapping region of line-scan digital camera, and is received by line-scan digital camera; Be far smaller than under the D condition at d, optical path difference is linear distribution in the light overlapping region, satisfies formula:

Δ＝xd/D，

Wherein x represents corresponding line-scan digital camera position;

Step 4 is carried out the interference light path difference and is proofreaied and correct, and optical path difference is expressed as: Δ '=2 Δ L ₁-(l ₁-l ₂)-xd/D, l ₁, l ₂Represent respectively arm of Mach Zehnder interferometer and No. two arms;

When Δ '=0, corresponding x position, output low coherence interference signal envelope peak value; After the adjustment of correction interferometer is finished, l ₁-l ₂Be constant, x is with Δ L ₁And change, and have one-to-one relationship, by accurate location x value, can realize the high precision demodulation of optical path difference to be measured.

6. the optical fiber Mechanical Study On Young Interference optical path difference demodulation method based on low coherence interference as claimed in claim 5 is characterized in that described step 4 also comprises: regulate between arm of Mach Zehnder interferometer and No. two arm two brachiums apart from l ₁-l ₂, realize the interval demodulation of different optical path differences.

7. such as the optical fiber Mechanical Study On Young Interference optical path difference demodulation method based on low coherence interference as claimed in claim 5, it is characterized in that described step 1 adopts the optical fiber Fabry-Perot interferometer to realize the optical path difference sensing, its interference light path difference sensing flow process comprises following operation:

The light that wideband light source is sent is by 2 * 2 three-dB couplers,, forms with reference to reflected light at fiber end face generating unit sub reflector along the light of Optical Fiber Transmission; Transmitted light by with fiber end face distance, delta L ₂Mirror reflects after again be coupled to optical fiber, form sensory reflex light, behind reflected light and sensory reflex light compositing light beam, comprised 2 Δ L ₂Optical path difference information, change catoptron apart from the distance of fiber end face, namely changed optical path difference sensing amount.

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