Asymmetric U-shaped optical fiber taper displacement sensor packaged by polymer film

Abstract

The invention discloses an asymmetric U-shaped optical fiber taper displacement sensor packaged by a polymer film. The displacement sensor comprises an asymmetric U-shaped optical fiber taper and a polymer film, wherein the asymmetric U-shaped optical fiber taper is packaged in the polymer film; wherein the asymmetric U-shaped optical fiber taper comprises two optical fiber taper areas and an asymmetric U-shaped taper waist area located between the two optical fiber taper areas. The asymmetric U-shaped optical fiber taper is completely embedded in the polymer (PDMS) film, and the PDMS film has relatively good flexibility, so that the stability of the obtained displacement sensor is effectively improved, simultaneous sensing of two parameters of micro displacement and temperature is realized, temperature crosstalk is effectively avoided, the sensitivity is also obviously improved, and the displacement sensor has good application prospects. And new technical support is expected to be provided for application scenes such as mechanical manufacturing, aerospace and biomedicine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber sensors, and particularly relates to a polymer film packaged asymmetric U-shaped optical fiber taper displacement sensor. BACKGROUND

[0002] In many fields, accurate measurement of displacement occupies an indispensable key position, such as in the mechanical manufacturing field, the machining precision of parts can be accurately controlled. In the field of aerospace, the measurement of displacement is directly related to the stability and safety of the aircraft. In the biomedical field, cell growth monitoring, blood vessel imaging and the like can be accurately monitored. Therefore, it is particularly important to design a high-precision and high-sensitivity displacement sensor.

[0003] At present, there are various displacement sensors on the market, such as laser displacement sensors, linear variable differential transformers, eddy current displacement sensors and the like. However, these sensors generally have the problems of being heavy and susceptible to electromagnetic interference. The optical fiber displacement sensor can effectively avoid the above problems and has the unique advantage of high sensitivity. According to the working principle, the optical fiber displacement sensor mainly includes: an optical fiber Bragg grating sensor, a Mach-Zehnder (M-Z) sensor, a Fabry-Pérot interferometer (F-P) sensor and a Michelson sensor. Among them, the M-Z optical fiber displacement sensor is usually prepared by methods such as drawing the optical fiber into a taper, fusing the optical fiber into a microsphere and misaligning the optical fiber fusion. Due to the strong evanescent field of these structures, the response to displacement change is very sensitive, and it is particularly favored by researchers.

[0004] In 2014, the Shen team ("Optical fiber axial micro-displacement sensor based on Mach-Zehnder interferometer", C. Shen et al. Optics Express, vol. 22, no. 26, pp. 31984-31992, Dec. 29, 2014.) designed a displacement sensor based on the M-Z interference principle. The sensor is prepared by cascading a bow-tie optical fiber taper and a single-mode optical fiber misaligned structure. The sensitivity of the sensor reaches-1.89 dB / μm, but the sensor realizes displacement sensing by monitoring the intensity change in the spectrum, which is easily affected by the stability of the experimental device, affecting the measurement accuracy. For example, in 2025, the Wang team ("Asymmetric U-Shaped Fiber Taper Probe Based on Polydimethylsiloxane Wrapping for Simultaneous Measurement of Force and Temperature", J. Wang et al. IEEE Sensors Journal, vol. 25, no. 5, pp. 8301-8308, Mar 1, 2025.) prepared an optical fiber into an asymmetric U-shaped fiber structure, and encapsulated the fiber taper in a polydimethylsiloxane (Polydimethylsiloxane, abbreviated as PDMS) cylinder. The mechanical strength of the proposed structure has been significantly improved, but the size of the cylinder is larger, and the spectral shift caused by external stress or displacement change is not significant. Although these sensors have good displacement response characteristics, the sensitivity of the sensor is not high enough. SUMMARY

[0005] Based on the above technical problems, the present application provides a polymer film packaged asymmetric U-shaped fiber taper displacement sensor, by embedding the asymmetric U-shaped fiber taper into the polymer (PDMS) film, and the PDMS film has good flexibility, the obtained displacement sensor not only effectively improves the stability, but also realizes the simultaneous sensing of micro-displacement and temperature dual parameters, effectively avoids temperature interference, and the sensitivity is also obviously improved, which is expected to provide new technical support for mechanical manufacturing, aerospace, biomedicine and other application scenarios.

[0006] The polymer film packaged asymmetric U-shaped fiber taper displacement sensor provided by the present application comprises: an asymmetric U-shaped fiber taper and a polymer film for packaging the asymmetric U-shaped fiber taper; The asymmetric U-shaped optical fiber taper comprises two optical fiber taper regions and an asymmetric U-shaped waist region between the two optical fiber taper regions.

[0007] Preferably, the length of the asymmetric U-shaped optical fiber taper is 3000-4000 μm, and the bending radius is 800-1200 μm. Preferably, the diameter of the asymmetric U-shaped waist region in the asymmetric U-shaped optical fiber taper is 80-100 μm.

[0008] Preferably, the polymer film is a PDMS film with a thickness of 500-1000 μm.

[0009] The application further provides a preparation method of the asymmetric U-shaped optical fiber taper displacement sensor packaged by the polymer film. S1, two optical fibers are fused and then thinned into a taper to obtain a straight optical fiber taper; S2, the waist region of the straight optical fiber taper is bent into a U shape along a non-central part to obtain an asymmetric U-shaped optical fiber taper; S3, the asymmetric U-shaped optical fiber taper is placed on a carrier, polymer glue is added dropwise until the asymmetric U-shaped optical fiber taper is immersed, and then the asymmetric U-shaped optical fiber taper displacement sensor is obtained after solidification into a film.

[0010] Preferably, in step S1, after the two multimode optical fibers are fused, the two sides are stretched along the axial direction from the fusion part, and then the straight optical fiber taper is obtained after the tapering.

[0011] Preferably, in step S2, after the waist region of the straight optical fiber taper is heated and melted, one end is bent to the other end along the non-central part until they are parallel, and then the asymmetric U-shaped optical fiber taper is obtained.

[0012] Preferably, in step S3, the asymmetric U-shaped optical fiber taper is placed on a carrier covered with a tin foil film, polymer glue prepared by mixing a PDMS prepolymer and a curing agent is added dropwise, the asymmetric U-shaped optical fiber taper is immersed, and then the asymmetric U-shaped optical fiber taper displacement sensor is obtained after heating and solidification into a film. Preferably, the mass ratio of the PDMS prepolymer to the curing agent is 10:1. Preferably, the heating and solidification temperature is 90-110 ℃, and the time is 10-20 min.

[0013] The application further provides a displacement sensing system comprising the asymmetric U-shaped optical fiber taper displacement sensor or the asymmetric U-shaped optical fiber taper displacement sensor prepared by the preparation method.

[0014] Preferably, the displacement sensing system further comprises a broadband light source and a spectrum analyzer. The broadband light source and the spectral analyzer are respectively connected to the asymmetric U-shaped fiber optic cone in the asymmetric U-shaped fiber optic cone sensor.

[0015] The specific working principle of the sensor described in this invention is as follows: The incident light is split into two beams at the asymmetric U-shaped fiber taper. One beam propagates forward within the U-shaped fiber taper, while the other beam propagates forward within the PDMS thin film, forming the cladding mode. The two beams, after passing through different optical paths, recouple at the other end of the U-shaped fiber taper and interfere and superimpose within the multimode fiber. Due to the phase difference between the core mode and the cladding mode, according to the MZ interference principle, the phase difference Δ... φ It can be approximated as follows: Where, Δ n eff λ is the effective refractive index difference between the core mode and the cladding mode, L is the effective interference length of the asymmetric U-shaped fiber taper displacement sensor, and λ is the wavelength of the input light wave.

[0016] The free spectral range Δλ can be approximated as: It can be seen that, with the increase in interference length L The decrease in the free spectral range Δ λ It will increase. When Δ in equation (1) φ =(2 N +1)π (where N When the intervals are 1, 2, 3, ..., the center wavelengths of the interference peaks and valleys are represented as follows: in, λ N It is the first N The center wavelength of the interference valley.

[0017] When a displacement is applied to the MZ interferometer, both the effective refractive index and effective interference length of the MZ interferometer's modes will change accordingly. According to formula (3), the interference peaks and valleys will shift. Formula (3) for displacement Z The displacement sensitivity of the structure can be obtained by differentiation. S : As can be seen, the asymmetric U-shaped fiber optic cone displacement sensor described in this invention can be used for accurate displacement measurement.

[0018] In this invention, an asymmetric U-shaped fiber taper is first fabricated using fiber fusion tapering technology. The asymmetric U-shaped fiber taper interference structure and the stepped displacement monitoring module enable displacement measurement perpendicular to the fiber end face. Compared to fiber Bragg grating or long-period grating displacement sensors, it has a simple structure, does not require bulky monitoring equipment, and is small in size and lightweight, making it easy to install and integrate into various small devices or systems. Secondly, the asymmetric U-shaped fiber taper is completely encapsulated in a PDMS film. Since the asymmetric U-shaped fiber taper structure is completely embedded in the PDMS film, and the PDMS film has good flexibility, the stability of the resulting displacement sensor is effectively improved. Furthermore, it achieves simultaneous sensing of both minute displacement and temperature parameters, effectively avoiding the problem of temperature crosstalk.

[0019] Experimental tests revealed that the displacement sensitivities of the two interference peaks of the displacement sensor described in this invention are -0.0250 nm / μm and -0.0149 nm / μm, respectively, and the temperature sensitivities are 0.6372 nm / ℃ and 1.8636 nm / ℃, respectively. The displacement sensor features high sensitivity and good stability, and is expected to provide new technical support for applications in mechanical manufacturing, aerospace, biomedicine, and other fields. Attached Figure Description

[0020] Figure 1 The following are schematic diagrams illustrating the fabrication process of the displacement sensor described in this embodiment of the invention: (a) is a schematic diagram of two multimode optical fibers; (b) is a motion trajectory diagram of the straight fiber taper and the support; (c) is a schematic diagram of the asymmetric U-shaped fiber taper; and (d) is a schematic diagram of the displacement sensor. Figure 2 This is an enlarged schematic diagram of the displacement sensor described in an embodiment of the present invention; Figure 3 The following are optical images and spectra of the displacement sensor described in this embodiment of the invention before and after encapsulation with a PDMS film using an asymmetric U-shaped fiber taper: (a) Optical image before encapsulation with a PDMS film using an asymmetric U-shaped fiber taper; (b) Optical image after encapsulation with a PDMS film using an asymmetric U-shaped fiber taper; (c) Spectrum of the sensor before encapsulation with a PDMS film using an asymmetric U-shaped fiber taper; (d) Spectrum of the sensor after encapsulation with a PDMS film using an asymmetric U-shaped fiber taper. Figure 4 This is a diagram of the test device for the displacement sensing system corresponding to the displacement sensor described in the embodiment of the present invention; Figure 5 The displacement response characteristics of the displacement sensor described in this embodiment of the invention are shown in the following diagrams: (a) transmission interference spectrum under different displacements; (b) spectrum of transmission interference spectrum when the displacement is 0 μm; (c) transmission interference spectrum under different displacements after filtering; (d) linear fitting result diagram. Figure 6The temperature response characteristics of the displacement sensor described in the embodiment of the present invention are shown in the following diagrams: (a) is the transmission interference spectrum at different temperatures after filtering, and (b) is the linear fitting result diagram. Figure 7 This is a stability test diagram of the displacement sensor described in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0022] Example

[0023] In the PDMS thin-film encapsulated asymmetric U-shaped fiber taper displacement sensor described in the above embodiments, optical images of the asymmetric U-shaped fiber taper before and after PDMS thin-film encapsulation are shown below. Figure 3 As shown in ab. (Refer to...) Figure 3 From a, we can see that the total length of the asymmetric U-shaped fiber taper is 3588 μm, the diameter of the waist region of the asymmetric U-shaped taper is 90 μm, and the radius of curvature is 934 μm. (Refer to...) Figure 3 As shown in b, the U-shaped fiber displacement sensor encapsulated with PDMS film has a length of 2.00 cm, a width of 1.30 cm, and a thickness of 950 μm.

[0024] In the PDMS thin-film encapsulated asymmetric U-shaped fiber taper displacement sensor described in the above embodiments, the spectral patterns of the asymmetric U-shaped fiber taper before and after PDMS thin-film encapsulation are as follows: Figure 3 As shown in cd. (Refer to...) Figure 3 As shown in the diagram, before encapsulating the asymmetric U-shaped fiber taper with a PDMS film, its insertion loss was close to -50 dBm. After encapsulation, the loss decreased significantly to approximately -26 dBm. This is because PDMS can better confine the evanescent field in the taper region, reducing the leakage of light energy to the outside. Simultaneously, refractive index matching reduces the reflection loss at the fiber-medium interface (the interface reflection coefficient decreases as the refractive index difference decreases), thus significantly reducing energy loss during light transmission. Furthermore, after encapsulating the asymmetric U-shaped fiber taper with a PDMS film, the maximum contrast of the interference peaks in the spectrum is approximately 15 dB, showing no significant change in contrast compared to before encapsulation.

[0025] To test the displacement response characteristics of the PDMS thin-film encapsulated asymmetric U-shaped fiber optic taper displacement sensor described in the above embodiments, refer to... Figure 4 The displacement sensor was used to build a test platform, which consisted of one two-dimensional moving platform and two one-dimensional moving platforms. First, the displacement sensor was positioned according to... Figure 4The orientation is fixed on the one-dimensional moving platform 1. The position of the PDMS film is adjusted so that the U-shaped region of the asymmetric U-shaped fiber taper in the PDMS film protrudes from the edge of the one-dimensional platform. Then, the two-dimensional moving platform is fixed on the one-dimensional moving platform, as shown in the figure. Figure 4 With the orientation set, the two knobs of the two-dimensional moving platform are positioned in the X and Z directions, respectively. Adjust the one-dimensional platform and the two-dimensional moving platform so that the asymmetric U-shaped fiber cone is directly below the two-dimensional moving platform and in contact with the PDMS film. Adjusting the knob of the two-dimensional moving platform in the Z direction will apply force to the U-shaped fiber cone, causing it to displace. Finally, connect the two ends of the asymmetric U-shaped fiber cone in the displacement sensor to the broadband light source (SC-5-FC) and the spectrometer (AQ6370D), respectively, to obtain the displacement sensing system corresponding to the displacement sensor described in the embodiment.

[0026] Record the spectrum of the displacement sensor when the displacement is 0 μm. Adjust the knob of the two-dimensional moving platform in the Z direction to slowly move the platform along the negative Z-axis. Record the spectrum once every 10 small divisions of the vernier scale. Each spectrum corresponds to a displacement change of 100 μm. A total of 7 sets of spectral data of the displacement sensor at different displacements were recorded. The results are as follows: Figure 5 As shown in a. (Refer to...) Figure 5 As can be seen from a, the interference peaks in the interference spectrum are composed of low-frequency peaks modulated by high-frequency peaks. These high-frequency peaks affect the position of the center wavelength of the interference peaks, reducing measurement accuracy. Using Origin software, a Fourier transform was performed on the spectrum at 0 μm. The transformed spectrum is shown below. Figure 5 As shown in b. (Refer to...) Figure 5 b indicates that, for Figure 5 The seven sets of data in 'a' were low-pass filtered at 0.0355 Hz, and the resulting spectra are shown below. Figure 5 As shown in c. (Refer to...) Figure 5As shown in c, the high-frequency peaks are well filtered out, and as the displacement increases, the low-frequency interference peaks gradually shift to the left. The shift response characteristics of the interference peaks near 1450 nm (Peak 1) and 1480 nm (Peak 2) were monitored in detail. When the shifts were 0 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, and 600 μm, the center wavelengths of the Peak 1 interference peak were located at 1452.2093 nm, 1450.9302 nm, 1449.3798 nm, 1448.1008 nm, 1445.6105 nm, 1441.8605 nm, and 1436.2011 nm, respectively, shifting by 16.0079 nm. The center wavelengths of the Peak 2 interference peak were located at 1497.7519 nm, 1496.4312 nm, 1494.6514 nm, 1493.3333 nm, and 1491.7461 nm, respectively. The wavelengths of the two interference peaks at different displacements are 1490.2360 nm and 1488.9526 nm, with a shift distance of approximately 8.7993 nm; the center wavelength positions of the two interference peaks at different displacements are both within... Figure 5 The results are given in section d. Linear fitting was performed on the data points of the two interference peaks respectively, and the results are shown below. Figure 6 As shown in d, the linear fitting results show that the center wavelengths of the Peak 1 and Peak 2 interference peaks are negatively correlated with the displacement, with slopes of -0.0250 and -0.0149, respectively. Therefore, the displacement sensitivities of these two interference peaks are -0.0250 nm / μm and -0.0149 nm / μm, respectively, and the linear correlation coefficients are 0.9135 and 0.9887, respectively.

[0027] To test the temperature response characteristics of the PDMS thin-film encapsulated asymmetric U-shaped fiber optic taper displacement sensor described in the above embodiment, the displacement sensor was first placed in a temperature-controlled chamber (CK-80G), with the temperature increasing from 30 ℃ to 55 ℃ in 5 ℃ increments. The transmission interference spectrum at each temperature was recorded, resulting in a total of 6 sets of data. These 6 sets of data were then low-pass filtered at 0.0355 Hz. The filtered spectra were obtained at... Figure 6 The details of how Peak 1 and Peak 2 change with temperature are given in the analysis. (See reference...) Figure 6 As shown in Figure a, the interference peak of Peak 1 shifted from 1439.0511 nm to 1456.2021 nm, a shift of 17.151 nm; the interference peak of Peak 2 shifted from 1480.1100 nm to 1524.3798 nm, a shift of 44.2698 nm. Linear fitting was performed on these data points, and the fitting results are as follows: Figure 6 As shown in b. (Refer to...) Figure 5As shown in b, the temperature sensitivities of the two interference peaks, Peak 1 and Peak 2, reached 0.6372 nm / ℃ and 1.8636 nm / ℃, respectively.

[0028] When the ambient temperature and displacement change, Figure 6 a and Figure 7 By monitoring the responses of the two interference peaks to temperature and displacement, the center wavelength position of the interference peak changes, enabling simultaneous sensing of two parameters. An asymmetric U-shaped fiber optic taper sensor based on PDMS thin-film encapsulation can be implemented for simultaneous temperature and displacement measurement using the following matrix: In the equation, ΔZ and ΔT represent the changes in displacement and temperature in the environment, respectively. The unit of displacement is μm, and the unit of temperature is °C. The change in displacement in the environment is achieved by the movement of a two-dimensional moving platform, and the change in temperature is achieved by a temperature control box. Δλ1 and Δλ2 are the wavelength shifts of the two interference peaks Peak 1 and Peak 2 as a function of displacement and temperature, respectively, in nm. SZ1 and ST1 are the displacement sensitivity and temperature sensitivity of Peak 1, respectively. SZ1 is -0.0250 nm / μm, and ST1 is 0.6372 nm / ℃. SZ2 and ST2 are the displacement sensitivity and temperature sensitivity of Peak 2, respectively, which are -0.0149 nm / μm and 1.8636 nm / ℃.

[0029] Because of the excellent flexibility of PDMS films, asymmetric U-shaped fiber optic taper sensors encapsulated in PDMS films possess good mechanical strength. They can simultaneously sense both displacement and temperature parameters, providing a new technical approach for applications such as biological tissue engineering and ecological parameter monitoring, and have significant engineering application prospects, demonstrating good application potential in micro-displacement detection.

[0030] This invention successfully obtained a novel displacement sensor by encapsulating an asymmetric U-shaped fiber taper in a PDMS film. The displacement sensor fabrication process utilizes only fused taper technology, resulting in a simple and low-cost fabrication process. Furthermore, the asymmetric U-shaped fiber taper is completely encapsulated in the PDMS film, significantly improving its stability. This displacement sensor achieves simultaneous sensing of both displacement and temperature parameters. The displacement sensitivities of the two interference peaks, Peak 1 and Peak 2, are -0.0250 nm / μm and -0.0149 nm / μm, respectively, while the temperature sensitivities reach 0.6372 nm / °C and 1.8636 nm / °C, respectively. In contrast, the sensor disclosed in patent CN119394342A cannot achieve displacement sensing and measurement.

[0031] To test the stability of the asymmetric U-shaped fiber taper displacement sensor encapsulated in PDMS thin film as described in the above embodiment, the displacement was controlled to vary within the range of 0-600 μm. When the displacement changed by 600 μm, the displacement sensitivity of the interference peaks near 1450 nm and 1480 nm was -0.015 nm / μm and -0.009 nm / μm, respectively. Since the spectrometer resolution is ±0.01 nm, the minimum resolution is ±0.667 μm.

[0032] Because of the excellent flexibility of PDMS film, the U-shaped fiber optic taper sensor based on PDMS film encapsulation possesses good stability. When the displacement changes, the U-shaped fiber optic taper displacement sensor based on PDMS film encapsulation is placed in a constant temperature environment of 25 ℃, and the position change of the center wavelength near 1453 nm is observed. Data is recorded at 5-minute intervals. The data for each center wavelength are... Figure 7 Provided in [the document / reference]. ​ It can be seen that the center wavelength drifted by ±0.308 nm within the recording time of 195 min. Since the accuracy of the temperature control box is ±0.5 ℃, this offset is mainly caused by the temperature fluctuation of the temperature control box, indicating that the sensor has good stability.

[0033] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polymer thin film encapsulated asymmetric U-shaped fiber taper displacement sensor, characterized in that, The asymmetric U-shaped fiber taper and a polymer film encapsulating the asymmetric U-shaped fiber taper. The asymmetric U-shaped fiber taper comprises two fiber taper regions and an asymmetric U-shaped waist region between the two fiber taper regions. The asymmetric U-shaped fiber taper has a length of 3000-4000 μm and a bending radius of 800-1200 μm.

2. The polymer thin film encapsulated asymmetric U-shaped fiber taper displacement sensor of claim 1, wherein, The asymmetric U-shaped waist region in the asymmetric U-shaped fiber taper has a diameter of 80-100 μm.

3. The polymer thin film encapsulated asymmetric U-shaped fiber taper displacement sensor of claim 2, wherein, The polymer film is a PDMS film with a thickness of 500-1000 μm.

4. The polymer thin film encapsulated asymmetric U-shaped fiber taper displacement sensor according to any one of claims 1-3, wherein, The method comprises the following steps:

5. A method of fabricating an asymmetric U-shaped fiber taper displacement sensor encapsulated by a polymer film according to any one of claims 1-4, characterized in that, S1, two pieces of optical fiber are fused and then stretched into a taper to obtain a straight fiber taper; S2, the waist region of the straight fiber taper is bent into a U-shape along a non-central part to obtain an asymmetric U-shaped fiber taper; S3, the asymmetric U-shaped fiber taper is placed on a carrier, and a polymer glue solution is added dropwise until the asymmetric U-shaped fiber taper is immersed, and then a film is formed after solidification to obtain the asymmetric U-shaped fiber taper displacement sensor. In step S1, two pieces of multimode optical fiber are fused, and then stretched into a taper along the axial direction from the fusion joint to both sides.

6. The method for fabricating the polymer thin-film encapsulated asymmetric U-shaped fiber optic cone displacement sensor according to claim 5, characterized in that, In step S2, the waist region of the straight fiber taper is heated and melted, and then one end is bent to the other end along the non-central part until they are parallel to obtain the asymmetric U-shaped fiber taper.

7. The method for fabricating the polymer thin-film encapsulated asymmetric U-shaped fiber optic cone displacement sensor according to claim 5 or 6, characterized in that, In step S3, the asymmetric U-shaped fiber taper is placed on a carrier covered with a tin foil film, a polymer glue solution prepared by mixing a PDMS prepolymer and a curing agent is added dropwise, the asymmetric U-shaped fiber taper is immersed, and then a film is formed after heating and solidification to obtain the asymmetric U-shaped fiber taper displacement sensor.

8. The method of claim 5-7 for the preparation of a polymer thin film encapsulated asymmetric U-shaped fiber taper displacement sensor, characterized in that, Preferably, the mass ratio of the PDMS prepolymer to the curing agent is 10:

1. Preferably, the heating and solidification temperature is 90-110 ℃, and the time is 10-20 min. The asymmetric U-shaped fiber taper displacement sensor of any one of claims 1-4 or the asymmetric U-shaped fiber taper displacement sensor prepared by the preparation method of any one of claims 5-8.

9. A displacement sensing system characterized by, The displacement sensing system further comprises a broadband light source and a spectrum analyzer.

10. The displacement sensing system of claim 9, wherein, The broadband light source and the spectrum analyzer are connected to the asymmetric U-shaped fiber taper in the asymmetric U-shaped fiber taper displacement sensor, respectively. ​

Images