CN218002459U - Optical fiber strain sensor based on vernier effect - Google Patents
Optical fiber strain sensor based on vernier effect Download PDFInfo
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- CN218002459U CN218002459U CN202221290228.5U CN202221290228U CN218002459U CN 218002459 U CN218002459 U CN 218002459U CN 202221290228 U CN202221290228 U CN 202221290228U CN 218002459 U CN218002459 U CN 218002459U
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Abstract
The utility model discloses an optical fiber strain sensor based on vernier effect, which comprises a reference interferometer and a sensing interferometer which are arranged in parallel, wherein the reference interferometer and the sensing interferometer are Mach-Zehnder interferometers; the reference interferometer and the sensing interferometer comprise a first single-mode fiber, a second single-mode fiber, a few-mode fiber and a third single-mode fiber which are sequentially welded; the light beam is excited into a high-order mode and a fundamental mode through a second single-mode fiber; the few-mode fiber transmits a high-order mode and a fundamental mode to the third single-mode fiber; the high-order mode and the fundamental mode interfere in the third single-mode fiber; the utility model discloses a monitoring simultaneously only receives the wavelength drift volume of the reference interferometer transmission spectrum of temperature variation influence, and the wavelength drift volume of the big envelope of parallel signal who receives the influence of meeting an emergency and temperature variation simultaneously can demodulate out temperature and meet an emergency, has not only improved sensor strain sensitivity by a wide margin, and has eliminated the influence of temperature.
Description
Technical Field
The utility model belongs to the technical field of the optical fiber sensing, concretely relates to optic fibre strain sensor based on vernier effect.
Background
Compared with the traditional electronic sensor, the optical fiber sensor is favored by many scholars and researchers due to the advantages of simple structure, small volume, light weight, electromagnetic interference resistance, high sensitivity and the like. In recent years, in order to further improve the measurement sensitivity of the mach-zehnder sensor, the vernier effect has come into the sight of researchers. The vernier effect is initially applied to a vernier caliper barometer for improving the measurement accuracy, and is later applied to an optical device sensing system for amplifying the shift of a spectral resonance peak, so that the sensitivity of a photonic device can be improved. The mach-zehnder interference principle is widely used in optical interference tests because of its simple and stable characteristics in various interference principles, and the single physical parameter measured according to the mach-zehnder interference principle may be temperature, refractive index, pressure, strain, and the like.
However, most of the sensors based on the Mach-Zehnder interference principle have multi-parameter response, and accurate measurement of a single parameter is difficult, so that synchronous sensing of strain and temperature is one of the ways of realizing accurate measurement. At present, more and more researchers begin to research on a double-parameter measurement sensor, while the traditional multi-parameter sensor realizes simultaneous measurement of temperature and strain through a sensitivity measurement matrix, however, the sensor envelope based on the vernier effect is a single-frequency signal, and the sensitivity matrix cannot be used for realizing simultaneous measurement of temperature and strain, so that the cross sensitivity of temperature is eliminated.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide an optic fibre strain sensor based on vernier effect improves the strain sensitivity of sensor, has eliminated the influence of temperature.
In order to solve the problem, the utility model adopts the following technical scheme: an optical fiber strain sensor based on a vernier effect comprises a reference interferometer and a sensing interferometer which are arranged in parallel, wherein the reference interferometer and the sensing interferometer are Mach-Zehnder interferometers; the reference interferometer and the sensing interferometer comprise a first single-mode fiber, a second single-mode fiber, a few-mode fiber and a third single-mode fiber which are sequentially welded; the light beam is excited into a high-order mode and a fundamental mode through a second single-mode fiber; the few-mode fiber transmits a high-order mode and a fundamental mode to the third single-mode fiber; the higher-order mode and the fundamental mode interfere in the third single-mode fiber.
Further, the second single-mode fiber comprises a welding ball A and a welding ball B, and when the light beam is transmitted to the welding ball A through the first single-mode fiber, the light beam is excited into a high-order mode of a cladding in the second single-mode fiber; the beam is excited into a fundamental mode in the core as it passes through the solder ball a to the solder ball B.
Further, the reference interferometer and the sensing interferometer are connected in parallel through two 3dB couplers.
Further, the free spectral range FSR generated by the fiber strain sensor envelope Comprises the following steps:
wherein, FSR s Representing the free spectral range of the sensing interferometer; FSR r Representing the free spectral range of the reference interferometer.
Further, the vernier effect sensitivity amplification factor M of the optical fiber strain sensor is as follows:
further, when the external temperature changes, the transmission spectrum wavelength of the reference interferometer drifts, and the calculation formula of the drift amount Δ λ of the reference interferometer is as follows:
Δλ＝k 1T ΔT
in the formula, k 1T For the temperature sensitivity of the sensing interferometer, Δ T is expressed as a temperature change value.
Further, when the external temperature and strain change,the wavelength of the transmission spectrum of the sensing interferometer changes along with the change of the wavelength of the transmission spectrum of the sensing interferometer, and the drift quantity delta lambda of the wavelength of the transmission spectrum of the sensing interferometer Envelope(s) The calculation formula of (2) is as follows:
Δλ envelope(s) ＝k 2T ΔT+k 2ε Δε
In the formula, k 2T Is the temperature sensitivity of the sensing interferometer; k is a radical of 2ε For the strain sensitivity of the sensing interferometer, Δ ε is expressed as the strain change value.
Compared with the prior art, the utility model discloses the beneficial effect who reaches is:
on the one hand, the utility model discloses a reference interferometer and the sensing interferometer that connect in parallel and set up, reference interferometer and sensing interferometer are mach-zehnder interferometers; the wavelength drift amount of the transmission spectrum of the reference interferometer only affected by temperature change is monitored simultaneously, and the wavelength drift amount of the parallel signal large envelope affected by strain and temperature change can demodulate temperature and strain, so that the optical fiber strain sensor generates vernier effect and is calibrated, the strain sensitivity of the sensor is greatly improved, and the influence of temperature is eliminated.
On the other hand, the second single-mode fiber comprises a welding ball A and a welding ball B, and when the light beam is transmitted to the welding ball A through the first single-mode fiber, the light beam is excited into a high-order mode of a cladding in the second single-mode fiber; when the light beam is transmitted to the fusion ball B through the fusion ball A, the light beam is excited into a fundamental mode in the fiber core; interference can still be generated after the propagation distance is ensured to be increased through the second single-mode fiber.
Drawings
Fig. 1 is a schematic structural diagram of an optical fiber strain sensor based on a vernier effect according to an embodiment of the present invention;
in the figure: 1-a first single mode optical fiber; 2-a second single mode fiber; 21-fusion ball A; 22-fusion ball B; 3-few-mode optical fiber; 4-a third single mode fiber.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, and the following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.
In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
As shown in fig. 1, an embodiment of the present invention provides an optical fiber strain sensor based on a vernier effect, including a reference interferometer and a sensing interferometer that are arranged in parallel, where the reference interferometer and the sensing interferometer are mach-zehnder interferometers; the reference interferometer and the sensing interferometer comprise a first single-mode fiber 1, a second single-mode fiber 2, a few-mode fiber 3 and a third single-mode fiber 4 which are sequentially welded; the output end of the first single-mode fiber 1 is connected with the input end of the second single-mode fiber 2; the second single-mode fiber 2 comprises a welding ball A21 and a welding ball B22, and when light beams are transmitted to the welding ball A21 through the first single-mode fiber 1, the light beams are excited into a high-order mode of a cladding in the second single-mode fiber 2; when the light beam is transmitted to a fusion ball B22 through a fusion ball A21, the light beam is excited into a fundamental mode in a fiber core, and the few-mode fiber 3 transmits a high-order mode and the fundamental mode to the third single-mode fiber 4; the high-order mode and the fundamental mode are interfered in the third single-mode fiber 4, and the second single-mode fiber 2 can ensure that the interference can still be generated after the propagation distance is increased.
Superposing the optical signal in the sensing interferometer and the optical signal in the reference interferometer to generate a vernier effect and generate a large-interference envelope; the optical fiber strain sensor is connected with the isolator; keeping the sensor strain free, temperature sensitivity k to the reference interferometer by a computer only when the temperature changes 1T Calibrating to obtain the temperature sensitivity k of the reference interferometer by fitting the temperature variation-transmission spectrum valley wavelength shift curve 1T (ii) a Keeping the sensor strain free, the temperature sensitivity k to the parallel signal envelope of the optical fibre strain sensor only when the temperature changes 2T Calibrating, and fitting the temperature variation-envelope wave trough wavelength offset curve to obtain the temperature sensitivity k of the parallel signal envelope of the optical fiber strain sensor 2T (ii) a Keeping the initial temperature of the sensor unchanged, and only when the strain acts on the sensing interferometer, the strain sensitivity k of the parallel signal envelope of the optical fiber strain sensor 2ε Calibrating, and obtaining the strain sensitivity k of parallel signal envelope by fitting the strain-envelope wave trough wavelength offset curve 2ε 。
Free spectral Range FSR generated by the fiber Strain sensor envelope Comprises the following steps:
wherein, FSR s Representing the free spectral range of the sensing interferometer; FSR r Representing the free spectral range of the reference interferometer.
The vernier effect sensitivity amplification factor M of the optical fiber strain sensor is as follows:
when the outside temperature changes, the transmission spectrum wavelength of the reference interferometer generates drift, and the calculation formula of the drift amount delta lambda of the reference interferometer is as follows:
Δλ＝k 1T ΔT
in the formula, k 1T For the temperature sensitivity of the sensing interferometer, Δ T is expressed as a temperature change value.
When the external temperature and the strain change, the wavelength of the transmission spectrum of the sensing interferometer changes, and the wavelength drift quantity delta lambda of the transmission spectrum of the sensing interferometer Envelope (envelope) The calculation formula of (2) is as follows:
Δλ envelope (envelope) ＝k 2T ΔT+k 2ε Δε
In the formula, k 2T Is the temperature sensitivity of the sensing interferometer; k is a radical of formula 2ε For the strain sensitivity of the sensing interferometer, Δ ε is expressed as the strain change value.
The preparation of the sensing interferometer and the reference interferometer comprises the following steps:
removing the coating layers of the first single mode fiber 1 and the second single mode fiber 2, cleaning the first single mode fiber 1 and the second single mode fiber 2 with alcohol, respectively cutting 2cm of fiber without the coating layers by using a cutting knife, and flatly cutting the cutting surfaces at two ends of the first single mode fiber 1 and the second single mode fiber 2;
placing the well cut single mode fiber at one end of a fusion splicer for discharging; because the discharge power during manual discharge is larger than the power of common fusion, the process of melting and shrinking can occur on the cutting surface of the optical fiber, and a spherical state is further presented. Two small balls which are respectively welded are simultaneously placed at two ends of the welding machine for manual discharge to form a welding ball A21 and a welding ball B22;
cutting off redundant structures of the second single-mode optical fiber 2, and only keeping parts of a welding ball A21 and a welding ball B22;
removing the coating layer of the few-mode optical fiber 3, wiping the few-mode optical fiber with alcohol, cutting the optical fiber with 25.8cm of non-coating layer by using a cutting knife, and cutting the cutting surfaces at two ends to be flat. One end of the few-mode optical fiber 3 is in core-to-core fusion with one end of the fusion ball B22, and the other end of the few-mode optical fiber is in fusion with the third single-mode optical fiber 4; and packaging and protecting the manufactured sensing interferometer and the reference interferometer.
The embodiment of the utility model has the advantages that two sensing interferometers with similar and different FSRs are connected in parallel with the reference interferometer to generate the vernier effect, thereby greatly improving the strain sensitivity of the parallel sensor; the wavelength drift amount of the reference interferometer transmission spectrum only influenced by temperature change is monitored at the same time, and the wavelength drift amount of the parallel signal large envelope influenced by strain and temperature change can demodulate the temperature and the strain, so that the strain sensitivity of the sensor is greatly improved, and the influence of the temperature is eliminated.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. The optical fiber strain sensor based on the vernier effect is characterized by comprising a reference interferometer and a sensing interferometer which are arranged in parallel, wherein the reference interferometer and the sensing interferometer are Mach-Zehnder interferometers; the reference interferometer and the sensing interferometer comprise a first single-mode fiber, a second single-mode fiber, a few-mode fiber and a third single-mode fiber which are sequentially welded; the light beam is excited into a high-order mode and a fundamental mode by the second single-mode fiber; the few-mode fiber transmits a high-order mode and a fundamental mode to the third single-mode fiber; the higher-order mode and the fundamental mode interfere in the third single-mode fiber.
2. The vernier effect based optical fiber strain sensor as claimed in claim 1, wherein the second single mode fiber comprises a fusion ball a and a fusion ball B, and the light beam is excited into a high-order mode of a cladding in the second single mode fiber when being transmitted to the fusion ball a through the first single mode fiber; the beam is excited into a fundamental mode in the core as it passes through the solder ball a to the solder ball B.
3. A vernier effect based fibre optic strain sensor as claimed in claim 1 or 2 wherein the reference and sensing interferometers are connected in parallel by two 3dB couplers.
4. The vernier effect based fiber optic strain sensor of claim 1, wherein the free spectral range FSR generated by the fiber optic strain sensor is envelope Comprises the following steps:
wherein, FSR s Representing the free spectral range of the sensing interferometer; FSR r Representing the free spectral range of the reference interferometer.
5. The vernier effect based optical fiber strain sensor according to claim 4, wherein the vernier effect sensitivity amplification factor M of the optical fiber strain sensor is:
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116105778A (en) * | 2023-04-12 | 2023-05-12 | 广东海洋大学深圳研究院 | Optical fiber sensing system for synchronous measurement of temperature and salt |
| US11965821B1 (en) | 2023-04-12 | 2024-04-23 | Guangdong Ocean University | Optical fiber sensing system for temperature and salinity synchronous measurement |
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- 2022-05-27 CN CN202221290228.5U patent/CN218002459U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116105778A (en) * | 2023-04-12 | 2023-05-12 | 广东海洋大学深圳研究院 | Optical fiber sensing system for synchronous measurement of temperature and salt |
| US11965821B1 (en) | 2023-04-12 | 2024-04-23 | Guangdong Ocean University | Optical fiber sensing system for temperature and salinity synchronous measurement |
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