CN114184119A - Low-cost repeatedly-produced polarization-maintaining optical fiber end surface Michelson interference sensor - Google Patents
Low-cost repeatedly-produced polarization-maintaining optical fiber end surface Michelson interference sensor Download PDFInfo
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- CN114184119A CN114184119A CN202111650746.3A CN202111650746A CN114184119A CN 114184119 A CN114184119 A CN 114184119A CN 202111650746 A CN202111650746 A CN 202111650746A CN 114184119 A CN114184119 A CN 114184119A
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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Abstract
The invention discloses a low-cost reproducible polarization-maintaining optical fiber end surface Michelson interference sensor.A conducting optical fiber and a sensing optical fiber of the sensor adopt polarization-maintaining optical fibers and are used for maintaining the polarization state of the optical fibers; the free end of the sensing optical fiber consists of a part of inclined end surface and a part of vertical end surface, the inclined end surface and the sensing optical fiber shaft form an angle of 45 degrees, and light of the fiber core is vertically emitted or light which is vertically emitted into the fiber core is coupled into the fiber core; the light reflected by the vertical end face part of the fiber core is transmitted reversely, and the light reflected by the inclined end face part of the fiber core enters the fiber core again after being reflected by the outer wall of the cladding and interferes with the light reflected by the vertical end face to form the end face Michelson interferometer. The sensor structure can be used for measuring temperature or transverse stress, has repeatability, eliminates the influence of environmental disturbance on the polarization state of transmitted light, and improves the stability of the structure; low cost, simple preparation and compact structure.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a low-cost and reproducible optical fiber end surface Michelson interferometer sensor.
Background
The optical fiber interference sensor, which is a typical representative of the optical fiber sensor, is a type of optical device which is currently most widely used in practical applications and has the most mature mechanism. The sensor has the advantages of large dynamic range, high sensitivity, good stability, electromagnetic interference resistance, suitability for extreme environments, capability of realizing long-distance multiplexing and the like, and has wide application scenes in the fields of electric power traffic, biochemistry, aerospace, astronomical meteorology, microorganism detection and the like.
The optical fiber interference type sensor has various types, including a Fabry-Perot interference (FPI) sensor, a Michelson Interference (MI) sensor, a Mach-Zehnder interference (MZI) sensor and a Sagnac interference sensor, and the preparation method comprises the following steps: the Fabry-Perot interference (FPI) sensor is prepared by collimating two optical fibers by a capillary or fixing a reflecting membrane by a sleeve outside the end face of the optical fibers at a certain distance, the Mach-Zehnder interference (MZI) sensor is prepared by welding the optical fibers in a staggered mode, and the Sagnac interference sensor is prepared by a fusion method. Although the method for preparing the optical fiber interferometric sensor has low cost and high yield, the following problems exist: the repeatability is poor, the preparation randomness of the cutting and welding method is high, the consistency of the sizes of optical fiber structures is difficult to ensure during mass production, the interference optical path difference of the optical fiber interferometer prepared every time is difficult to keep consistent, and the sensors with almost consistent performance parameters are difficult to produce in batches, so that complicated calibration work needs to be carried out on different sensors. In addition, the structure with the damaged circular symmetry of part of the optical fiber has different responses to input light with different polarization states, and the stability of the output result is greatly reduced due to the polarization sensitivity of the structure. At present, the optical fiber interferometer sensors which can be produced in batches by accurately controlling the size only have the technologies of femtosecond laser processing, plasma beam etching and the like, but the processing technologies are generally high in cost and long in preparation period, so that the practicability of the optical fiber interferometer sensors is limited.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a polarization-maintaining optical fiber end surface Michelson interference sensor which is low in cost and capable of being repeatedly produced.
The low-cost reproducible polarization-maintaining optical fiber end surface Michelson interference sensor is characterized by comprising a conducting optical fiber and a sensing optical fiber which are connected; the conducting optical fiber and the sensing optical fiber are polarization maintaining optical fibers and comprise a cladding and a fiber core; the free end of the sensing optical fiber consists of a part of 45-degree inclined end surface and a part of vertical end surface, the fiber core end surface of the sensing optical fiber also consists of an inclined part and a vertical part, and the fiber core end surface forms a beam splitter; the outer wall of the optical fiber cladding provides a reflecting surface; the inclined end face and the sensing optical fiber shaft form an angle of 45 degrees, and light of the fiber core is vertically emitted or light which is vertically emitted into the fiber core is coupled into the fiber core; the light reflected by the vertical end face part of the fiber core is transmitted reversely, and the light reflected by the inclined end face part of the fiber core enters the fiber core again after being reflected by the outer wall of the cladding and interferes with the light reflected by the vertical end face to form the end face Michelson interferometer.
The polarization maintaining optical fiber is in a non-circular symmetrical structure, has a double refraction effect, has a fast axis direction and a slow axis direction, can maintain the polarization state of transmitted light, and can ensure that polarization related devices have stable output. .
The inclined end face is parallel to the slow axis of the polarization maintaining fiber.
The interference optical path difference of the Michelson interferometer is determined by the drawing process of the optical fiber and is not influenced by the preparation process of the sensor.
The sensor employs wavelength demodulation and can be used to measure temperature and lateral pressure.
The side edge of the fiber core of the polarization-maintaining optical fiber can be chiseled into a hollow hole, light reflected by the inclined end surface of the fiber core penetrates through the hollow hole, and the sensor is used for measuring the refractive index of a medium in the hole.
The invention has the beneficial effects that:
the polarization maintaining optical fiber end surface Michelson interference sensor which is low in cost and capable of being repeatedly produced can achieve mass production, and parameters of the optical fiber Michelson sensor produced each time can be kept consistent in height; the polarization sensitivity of the structure is considered, the influence of environmental disturbance on the polarization state of the transmitted light is eliminated, and the stability of the structure is greatly improved; the cost is low, the preparation process is simple, the yield is high, and the production period is short; the full optical fiber structure is more compact.
Drawings
Fig. 1 is a schematic diagram of a polarization maintaining fiber end surface michelson interferometric sensor according to an embodiment of the present invention, (a) a schematic diagram of a polarization maintaining fiber end surface, and (b) a schematic diagram of a cross-sectional optical path.
The optical fiber comprises 1-polarization maintaining optical fiber, 2-optical fiber core, 3-optical fiber cladding, 4-slow axis, 5-fast axis, 5-polarization maintaining optical fiber refractive index modulation region, 6-inclined end face part, 7-vertical end face part and 8-cladding side wall reflecting surface.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 1, in the present embodiment, a polarization maintaining fiber 1 is used as the sensing fiber. One end of the polarization maintaining optical fiber 1 is polished to form an inclined end surface 6 and a vertical end surface 7, the inclined angle of the inclined end surface 6 is 45 degrees, a part of light of the optical fiber core 2 can be vertically emitted into the optical fiber cladding 3 by rotating 90 degrees, the light is incident on the reflecting surface 8 of the cladding side wall of the optical fiber and is vertically reflected back to the inclined end surface, and then returns to the optical fiber core 2 and is transmitted back; the vertical end face 7 reflects a portion of the light from the fiber core 2 directly back to the transmission, thereby forming a michelson interferometer at the fiber end face.
In particular, light reflected by the perpendicular end face 7 of the optical fiber
Returning directly to the core 2 and transmitting back light reflected by the angled end face 6
Will be incident normally on the cladding side wall reflective surfaces 8,and is reflected back again to the angled end face 6 and re-coupled into the core 2 and the core
Interference occurs, and the interference phase difference of the two beams can be expressed as:
wherein
Is the interference optical path difference of the two beams of light,
the size of the optical fiber is directly determined, and the optical fiber is not influenced by the processing technology;
the light of different polarization directions has different initial phase differences for the initial phase differences of the interfering light.
Further analysis, assuming that the sensing structure is made of a non-polarization-maintaining optical fiber, the s light and the p light reflected by the inclined end surface 6 have different phase differences when interfering, and when the s light and the p light are transmitted in the non-polarization-maintaining optical fiber (for example, a common standard single-mode optical fiber), the s light and the p light are coupled with each other, the coupling condition is random, and the interference spectrum is also unstable under the influence of the defects of the optical fiber and the external environment disturbances such as stress, bending, torsion, vibration and the like of the optical fiber.
The polarization maintaining fiber 1 has a high birefringence effect, which is explained in detail by the fact that the fiber has different refractive indexes for light with the polarization direction along the fast axis 5 and light with the polarization direction along the slow axis 4, and the polarized light along the fast axis 5 and the slow axis 4 are not coupled with each other when the light is transmitted in the polarization maintaining fiber 1.
Based on the fresnel reflection law, the phase jump edges of the light with different polarization directions after being reflected by the inclined end surface 6 are different, so that the inclined end surface 6 is parallel to the slow axis 4 of the polarization-maintaining fiber 1 during preparation, that is, the polarization direction of the p light component (the polarization direction is parallel to the reflection surface) is parallel to the slow axis 4 when the light is reflected by the inclined end surface 6, and the polarization direction of the s light component (the polarization direction is perpendicular to the reflection surface) is parallel to the fast axis 5, so that when the interference occurs, the interference of the p light and the s light is independent and cannot be coupled with each other, the transmission of the polarization state cannot be influenced by the environmental disturbance, and the structure has stable output response.
Because the optical path difference of the interference light is only influenced by the size and the refractive index of the optical fiber, the sensor prepared each time can have the same parameters, and the method has the advantage of repeatable production.
The sensor may be used to measure temperature or lateral stress, in particular, changes in temperature or lateral stress that alter the lateral dimensions of the fibre and the refractive index of the fibre cladding 3, whereby changes in temperature or stress can be judged by drift of the interference spectrum.
The low-cost reproducible polarization maintaining optical fiber end surface Michelson interference sensor provided by the embodiment can be manufactured by the following preparation method:
1) after the polarization maintaining fiber 1 is cut flat, the polarization maintaining fiber is placed into a microscope for observation, and the directions of the fast axis 4 and the slow axis 5 are determined.
) And (3) after the polarization maintaining optical fiber 1 is clamped, putting the polishing machine on the polarization maintaining optical fiber to ensure that the included angle between the flattened end surface and the abrasive paper is about 45 degrees, and the slow shaft 5 is parallel to the polishing plane, and starting the polishing machine.
) And directly observing the inclined end face 6 of the polarization maintaining optical fiber 1 through a microscope, observing whether an interference spectrum exists in the reflection spectrum, judging whether the inclined angle of the inclined end face 6 is 45 degrees or not and whether a boundary line between the inclined end face 6 and the vertical end face 7 just passes through the fiber core 2 or not, and if not, adjusting the included angle between the polarization maintaining optical fiber 1 and the abrasive paper, and repeating the steps until the interference spectrum appears.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.
Claims (6)
1. The low-cost reproducible polarization maintaining optical fiber end surface Michelson interference sensor is characterized by comprising a conducting optical fiber and a sensing optical fiber which are connected;
the conducting optical fiber and the sensing optical fiber are polarization maintaining optical fibers and comprise a cladding and a fiber core;
the free end of the sensing optical fiber consists of a part of 45-degree inclined end surface and a part of vertical end surface, the fiber core end surface of the sensing optical fiber also consists of an inclined part and a vertical part, and the fiber core end surface forms a beam splitter; the outer wall of the optical fiber cladding provides a reflecting surface; the inclined end face and the sensing optical fiber shaft form an angle of 45 degrees, and light of the fiber core is vertically emitted or light which is vertically emitted into the fiber core is coupled into the fiber core; the light reflected by the vertical end face part of the fiber core is transmitted reversely, and the light reflected by the inclined end face part of the fiber core enters the fiber core again after being reflected by the outer wall of the cladding and interferes with the light reflected by the vertical end face to form the end face Michelson interferometer.
2. The optical fiber end-face michelson interferometer sensor of claim 1, wherein the polarization maintaining fiber is non-circularly symmetric, has birefringence effect, and has fast axis direction and slow axis direction, so as to maintain polarization state of transmitted light and ensure stable output of polarization dependent device.
3. The fiber-optic endface michelson interferometer sensor of claim 1, wherein the angled endface is parallel to the polarization maintaining fiber slow axis.
4. The michelson interferometer sensor at an end face of an optical fiber according to claim 1, wherein the interference path difference of the michelson interferometer is determined by a drawing process of the optical fiber and is not affected by a manufacturing process of the sensor.
5. The fiber-optic endface michelson interferometer sensor of claim 1, wherein the sensor employs wavelength demodulation for measuring temperature and lateral pressure.
6. The fiber-optic endface michelson interferometer sensor of claim 1, wherein the side of the core of the polarization maintaining fiber is chiseled to form an open hole through which light reflected from the angled endface of the core will pass, the sensor being adapted to measure the refractive index of the medium in the hole.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114812445A (en) * | 2022-05-20 | 2022-07-29 | 合肥师范学院 | Plane deflection angle measuring device and method based on double-cavity FP interferometer |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114812445A (en) * | 2022-05-20 | 2022-07-29 | 合肥师范学院 | Plane deflection angle measuring device and method based on double-cavity FP interferometer |
| CN114812445B (en) * | 2022-05-20 | 2023-08-22 | 合肥师范学院 | Plane deflection angle measuring device and method based on dual-cavity FP interferometer |
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