Optical fiber strain sensing system based on harmonic vernier effect

Abstract

The utility model belongs to the field of optical fiber sensing, and particularly relates to an optical fiber strain sensing system based on a harmonic vernier effect, which comprises a system body, the system body comprises a wide-spectrum light source, the output end of the wide-spectrum light source is electrically connected with a sensing head, the output end of the sensing head is electrically connected with a spectrum analyzer, and the spectrum analyzer is electrically connected with the optical fiber strain sensor. The sensing head comprises a Mach-Zehnder interferometer and a Sagnac interferometer; through the system body, the defects that a traditional electromagnetic sensor is easily interfered by an electromagnetic field and is inconvenient to integrate and reuse and the like can be effectively overcome, a harmonic vernier effect is introduced into the optical fiber strain sensing head body, and the sensitivity and the resolution of strain measurement of the optical fiber strain sensing head body are effectively improved; and meanwhile, the limitation of the common vernier effect on the amplification factor can be overcome, so that the sensitivity of the sensor is amplified by hundreds of times, the amplification factor can be better controlled, and the size of the sensing head can be more flexibly designed according to requirements.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of optical fiber sensing, and specifically relates to an optical fiber strain sensing system based on harmonic vernier effect. BACKGROUND

[0002] In human production, building safety monitoring is very important, with the rapid development of science and technology, the types of strain sensors are more and more, and most of the traditional strain sensors are electromagnetic sensors, which are generally large in size and are not conducive to the integration and reuse of sensors in technology, and are not convenient for networking and other defects, and are gradually replaced by optical fiber strain sensors, which have the characteristics of light weight, small size, corrosion resistance, electromagnetic interference resistance, good chemical stability, intrinsic safety, etc., and are suitable for safety monitoring of building structures in strong electromagnetic interference, flammable and explosive, strong corrosive and other dangerous and extreme environments.

[0003] Due to the influence of the sensing head of the ordinary optical fiber strain sensor by its own characteristic factors, the strain sensitivity is generally limited, and the manufacturing equipment has high requirements and the manufacturing technology is complex, the optical fiber strain sensing head based on harmonic vernier effect can effectively amplify and improve the sensitivity and resolution on the basis of effectively improving the sensitivity and resolution of the strain sensor, and has low requirements on the manufacturing equipment, simple and flexible manufacturing method. UTILITY MODEL CONTENT

[0004] In order to make up for the shortcomings of the prior art, due to the influence of the sensing head of the ordinary optical fiber strain sensor by its own characteristic factors, the strain sensitivity is generally limited, and the manufacturing equipment has high requirements and the manufacturing technology is complex, the utility model provides an optical fiber strain sensing system based on harmonic vernier effect.

[0005] The utility model solves the technical scheme that adopts: an optical fiber strain sensing system based on harmonic vernier effect, including system body, the system body includes wide spectrum light source, the output of wide spectrum light source is connected with sensing head in electric property, the output of sensing head is connected with optical spectrum analyzer in electric property;

[0006] The sensing head includes a Mach-Zehnder interferometer and a Sagnac interferometer, the output of the wide spectrum light source is electrically connected with the input of the Mach-Zehnder interferometer, the output of the Mach-Zehnder interferometer is electrically connected with the input of the Sagnac interferometer, and the output of the Sagnac interferometer is electrically connected with the input of the optical spectrum analyzer.

[0007] As preferred, the Mach-Zehnder interferometer comprises a first single-mode pigtail, one end of the first single-mode pigtail is welded with a first multi-mode optical fiber, one end of the first multi-mode optical fiber is welded with a high numerical aperture single-mode optical fiber, one end of the high numerical aperture single-mode optical fiber is welded with a second multi-mode optical fiber, one end of the second multi-mode optical fiber is welded with a second single-mode pigtail.

[0008] As preferred, the Sagnac interferometer comprises a polarization maintaining optical fiber, one end of the polarization maintaining optical fiber is electrically connected with a polarization controller, and an output end of the polarization controller is electrically connected with a 3dB optical fiber coupler.

[0009] As preferred, an isolator is arranged between the Mach-Zehnder interferometer and the Sagnac interferometer, an output end of the Mach-Zehnder interferometer is electrically connected with an input end of the isolator, and an output end of the isolator is electrically connected with an input end of the Sagnac interferometer.

[0010] As preferred, the first single-mode pigtail and the second single-mode pigtail both have the following parameters: an outer diameter of 125 microns and a core diameter of 9 microns.

[0011] As preferred, the first multi-mode optical fiber and the second multi-mode optical fiber both have the following parameters: an outer diameter of 125 microns and a core diameter of 50 microns.

[0012] As preferred, the high numerical aperture single-mode optical fiber has the following parameters: an outer diameter of 125 microns and a core diameter of 2 microns.

[0013] The utility model discloses a beneficial effect lies in:

[0014] The system body can effectively overcome the defects of traditional electromagnetic sensors, such as being susceptible to electromagnetic field interference, inconvenient integration and reuse, introduces harmonic vernier effect in the optical fiber strain sensing head body, effectively improves the sensitivity and resolution of the optical fiber strain sensing head body strain measurement, can overcome the limitation of ordinary vernier effect on amplification multiple, makes the sensor sensitivity be amplified by hundreds of times, and can better control the amplification multiple and more flexibly design the sensing head size according to the requirement. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained according to these drawings without creating creative labor.

[0016] Figure 1 The strain sensing optical path diagram for the realization of the utility model is shown in the figure.

[0017] Figure 2 The structural diagram of the Mach-Zehnder interferometer of the utility model;

[0018] Figure 3 The structural diagram of the Sagnac interferometer of the utility model.

[0019] In the figure: 1, system body; 2, sensing head; 21, Mach-Zehnder interferometer; 2101, first single-mode tail fiber; 2102, first multimode optical fiber; 2103, high numerical aperture single-mode optical fiber; 2104, second multimode optical fiber; 2105, second single-mode tail fiber; 22, Sagnac interferometer; 2201, polarization maintaining optical fiber; 2202, polarization controller; 2203, 3dB fiber coupler; 3, optical spectrum analyzer; 4, isolator; 5, wide spectrum light source. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0021] The following will be combined with the drawings Figures 1-3 The application will be further described in detail,

[0022] The embodiment of the application discloses a fiber strain sensing system based on harmonic vernier effect. Figures 1-3 A fiber strain sensing system based on harmonic vernier effect, comprising a system body 1, the system body 1 includes a wide spectrum light source 5, the output end of the wide spectrum light source 5 is electrically connected with a sensing head 2, the output end of the sensing head 2 is electrically connected with an optical spectrum analyzer 3;

[0023] The sensing head 2 includes a Mach-Zehnder interferometer 21 and a Sagnac interferometer 22, the output end of the wide spectrum light source 5 is electrically connected with the input end of the Mach-Zehnder interferometer 21, the output end of the Mach-Zehnder interferometer 21 is electrically connected with the input end of the Sagnac interferometer 22, and the output end of the Sagnac interferometer 22 is electrically connected with the input end of the optical spectrum analyzer 3.

[0024] Refer to Figure 2, the Mach-Zehnder interferometer 21 includes a first single-mode tail fiber 2101, one end of the first single-mode tail fiber 2101 is welded with a first multi-mode optical fiber 2102, one end of the first multi-mode optical fiber 2102 is welded with a high numerical aperture single-mode optical fiber 2103, one end of the high numerical aperture single-mode optical fiber 2103 is welded with a second multi-mode optical fiber 2104, one end of the second multi-mode optical fiber 2104 is welded with a second single-mode tail fiber 2105, and the Mach-Zehnder interferometer 21 is sequentially welded by the first single-mode tail fiber 2101, the first multi-mode optical fiber 2102, the high numerical aperture single-mode optical fiber 2103, the second multi-mode optical fiber 2104 and the second single-mode tail fiber 2105, realizing inter-mode interference of the optical signal and preliminarily modulating the optical signal;

[0025] With reference to Figure 1 and Figure 3 , the Sagnac interferometer 22 includes a polarization maintaining optical fiber 2201, one end of the polarization maintaining optical fiber 2201 is electrically connected with a polarization controller 2202, an output end of the polarization controller 2202 is electrically connected with a 3dB fiber coupler 2203, the polarization maintaining optical fiber 2201 maintains the polarization state of the optical signal, the polarization controller 2202 adjusts the polarization direction of the optical signal, and the 3dB fiber coupler 2203 realizes cyclic interference of the optical signal and further modulates the optical signal;

[0026] With reference to Figure 1 , the isolator 4 is arranged between the Mach-Zehnder interferometer 21 and the Sagnac interferometer 22, an output end of the Mach-Zehnder interferometer 21 is electrically connected with an input end of the isolator 4, an output end of the isolator 4 is electrically connected with an input end of the Sagnac interferometer 22, the isolator 4 is located between the Mach-Zehnder interferometer 21 and the Sagnac interferometer 22, prevents reflection of the optical signal, ensures unidirectional transmission of the signal, and improves system stability;

[0027] With reference to Figure 2 , the first single-mode tail fiber 2101 and the second single-mode tail fiber 2105 both have an outer diameter of 125 microns and a core diameter of 9 microns, and by setting the parameters of the first single-mode tail fiber 2101 and the second single-mode tail fiber 2105, single-mode transmission of the optical signal is ensured;

[0028] With reference to Figure 2 , the first multi-mode optical fiber 2102 and the second multi-mode optical fiber 2104 both have an outer diameter of 125 microns and a core diameter of 50 microns, and by setting the parameters of the first multi-mode optical fiber 2102 and the second multi-mode optical fiber 2104, a plurality of transmission modes required for inter-mode interference are provided;

[0029] With reference to Figure 2 , the high numerical aperture single-mode optical fiber 2103 has an outer diameter of 125 microns and a core diameter of 2 microns, and by setting the parameters of the high numerical aperture single-mode optical fiber 2103, the interaction between the optical signal and the optical fiber material is enhanced, and the interference effect is optimized.

[0030] Working principle: the first single-mode fiber tail 2101 is the input channel of light, which introduces the light of the broadband light source 5 into the Mach-Zehnder interferometer 21, the first multimode fiber 2102 has a larger core diameter, so that the light can be coupled into the cladding and core of the high numerical aperture single-mode fiber 2103 respectively, which provides the basis for interference effect, the high numerical aperture single-mode fiber 2103 provides a larger cladding and core refractive index difference, while maintaining single-mode propagation of light, the second multimode fiber 2104 is the coupling place of the output light of the high numerical aperture single-mode fiber 2103, which provides the condition for the interference of light, the second single-mode fiber tail 2105 is the output channel of the Mach-Zehnder interferometer 21, which guides the interfered light out, the Sagnac interferometer 22 further interferes the light output from the Mach-Zehnder interferometer 21, the interference frequency of the Sagnac interferometer 22 and the Mach-Zehnder interferometer 21 is matched to produce harmonic vernier effect, which enhances the strain sensitivity of the fiber strain sensing system 1, the spectrum analyzer 3 is the terminal of the fiber strain sensing head 2 body, which is used for analyzing and recording the spectral information output from the Sagnac interferometer 22, so as to realize the measurement of strain and other parameters, the high numerical aperture single-mode fiber 2103 has a larger refractive index difference between the high numerical single-mode fiber cladding and the core, which effectively shortens the size of the Mach-Zehnder interferometer 21, the polarization maintaining fiber 2201 with high sensitivity to strain is used to build the Sagnac ring as the fiber strain sensing head 2 body, the interference frequency of the two is matched, and the harmonic vernier effect is formed by cascading the two, which effectively improves the sensitivity and resolution of the strain sensing.

[0031] The basic principle, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A fiber optic strain sensing system based on harmonic Vernier effect, characterized by: The system comprises a system body (1), the system body (1) comprises a wide spectrum light source (5), the output end of the wide spectrum light source (5) is electrically connected with a sensing head (2), the output end of the sensing head (2) is electrically connected with a spectrum analyzer (3); The sensing head (2) comprises a Mach-Zehnder interferometer (21) and a Sagnac interferometer (22), the output end of the wide spectrum light source (5) is electrically connected with the input end of the Mach-Zehnder interferometer (21), the output end of the Mach-Zehnder interferometer (21) is electrically connected with the input end of the Sagnac interferometer (22), and the output end of the Sagnac interferometer (22) is electrically connected with the input end of the spectrum analyzer (3).

2. The fiber optic strain sensing system based on harmonic Vernier effect according to claim 1, wherein: The Mach-Zehnder interferometer (21) comprises a first single-mode tail fiber (2101), one end of the first single-mode tail fiber (2101) is welded with a first multi-mode optical fiber (2102), one end of the first multi-mode optical fiber (2102) is welded with a high numerical aperture single-mode optical fiber (2103), one end of the high numerical aperture single-mode optical fiber (2103) is welded with a second multi-mode optical fiber (2104), and one end of the second multi-mode optical fiber (2104) is welded with a second single-mode tail fiber (2105).

3. The fiber optic strain sensing system based on harmonic Vernier effect according to claim 1, wherein: The Sagnac interferometer (22) comprises a polarization maintaining optical fiber (2201), one end of the polarization maintaining optical fiber (2201) is electrically connected with a polarization controller (2202), and the output end of the polarization controller (2202) is electrically connected with a 3dB optical fiber coupler (2203).

4. The fiber optic strain sensing system based on harmonic Vernier effect according to claim 1, wherein: An isolator (4) is arranged between the Mach-Zehnder interferometer (21) and the Sagnac interferometer (22), the output end of the Mach-Zehnder interferometer (21) is electrically connected with the input end of the isolator (4), and the output end of the isolator (4) is electrically connected with the input end of the Sagnac interferometer (22).

5. The fiber optic strain sensing system based on harmonic Vernier effect according to claim 2, wherein: The first single-mode tail fiber (2101) and the second single-mode tail fiber (2105) have the following parameters: an outer diameter of 125 microns and a core diameter of 9 microns.

6. The fiber optic strain sensing system based on harmonic Vernier effect according to claim 2, wherein: The first multi-mode optical fiber (2102) and the second multi-mode optical fiber (2104) have the following parameters: an outer diameter of 125 microns and a core diameter of 50 microns.

7. The fiber optic strain sensing system based on harmonic Vernier effect according to claim 2, wherein: The high numerical aperture single-mode optical fiber (2103) has the following parameters: an outer diameter of 125 microns and a core diameter of 2 microns.

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