Optical fiber structure and system capable of simultaneously measuring curvature and temperature and manufacturing method

Abstract

The invention discloses an optical fiber structure and system capable of simultaneously measuring curvature and temperature and a manufacturing method, and relates to the technical field of communication. The optical fiber structure capable of simultaneously measuring the curvature and the temperature is manufactured by forming a dislocation structure through the central axis of the single-mode optical fiber and connecting the dislocation structure with the optical fiber adapter, the optical fiber structure is simple in manufacturing process, stable in performance, low in price and high in precision, and the curvature sensitivity and the temperature sensitivity can be measured by demodulating the MZI wavelength sensitive to the temperature and the anti-resonance reflection waveguide strength. The problem of cross sensitivity of curvature and temperature is solved. Two different sensing mechanisms are combined, joint demodulation is carried out, and the device can be used for simultaneous sensing test of temperature and curvature.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber structures, and in particular to an optical fiber structure, system and manufacturing method capable of simultaneously measuring curvature and temperature. Background Art

[0002] Curvature is a very important physical parameter that needs to be monitored in many applications such as aerospace, robotics, and structural health monitoring. In traditional curvature measurement schemes, piezoresistive or piezoelectric electronic strain gauges are mainly used, which not only have low costs but also can be used more flexibly. However, their disadvantages are that they cannot measure larger curvatures and cannot be used at higher temperatures. Fiber optic structures based on interferometer structures, such as FP interferometer, Sagnac interferometer, MZ interferometer, and MI interferometer, have inherent advantages such as high sensitivity, low cost, simple structure, anti-electromagnetic interference, and high temperature resistance. Therefore, they have received extensive attention from researchers in curvature measurement.

[0003] Single Mode Fiber: The central glass core is very thin (core diameter is generally 9 or 10 μm), and there is only one transmission mode of the fiber. The transmission loss and transmission dispersion of single mode fiber are relatively small. The small transmission loss can make the signal transmit farther in the fiber, and the small transmission dispersion is conducive to the transmission of high-speed and large-capacity data.

[0004] Fiber optic connector (HST) is the most widely used optical passive device in fiber optic communication systems. Most fiber optic connectors are composed of three parts: two fiber connectors and a coupler. The two fiber connectors are installed into the tail ends of the two optical fibers; the coupler serves as an alignment sleeve. In addition, the coupler is often equipped with a metal or non-metal flange to facilitate the installation and fixation of the connector. The optical fibers are connected by the adapter through the open sleeve inside it to ensure the highest connection performance between the fiber optic connectors. In order to fix it on various panels, a variety of fine fixing flanges are also designed. The two ends of the conversion adapter can connect fiber optic connectors of different interface types, and provide connections between APC end faces. Duplex or multi-connection adapters can increase installation density and save space.

[0005] According to the demodulation method, the fiber curvature fiber structure can be divided into: intensity modulation type, phase modulation type and frequency modulation type. Among them, the intensity modulation type mainly uses the optical loss caused by the bending of the optical fiber to realize the sensing measurement of the curvature. The light intensity modulation type has a simple manufacturing process, but there are problems such as low measurement accuracy. The phase modulation type fiber curvature fiber structure is an MZI composed of a core mode and a cladding mode. It is characterized by high sensing accuracy but is easily affected by temperature. The frequency modulation type mainly uses a fiber grating structure, but this type of fiber structure has a high manufacturing cost and low mechanical strength. Summary of the invention

[0006] The purpose of the present invention is to overcome the cross-sensitivity problem of curvature and temperature in the prior art and to provide a method for manufacturing an optical fiber structure for simultaneously measuring curvature and temperature.

[0007] The objective of the present invention is achieved through the following technical solutions: A method for manufacturing an optical fiber structure capable of simultaneously measuring curvature and temperature, the method comprising: S1. Use fiber pliers to strip the coating of the two ends of the two SMFs, with a length of 0-2 cm each, wipe them clean with cotton dipped in alcohol, use a fiber cleaver to cut the two ends of the two SMFs evenly, then put the two SMFs with the coating stripped off into the fiber fusion splicer and close the clamp; S2. Move the motor to adjust the position distance between the two end faces of the two SMF segments to 4 μm, set the discharge parameters of the optical fiber fusion splicer, and discharge to make the two end faces of the two SMF segments to be staggered and fused; S3. Place the welded structure on the displacement platform and cut it off at 300 μm away from the dislocated structure; S4. Use fiber optic pliers to peel off the HST coating layer, the length of which is in the range of 0-1.5cm, wipe it clean with cotton dipped in alcohol, cut the two end faces of the HST flat with a fiber optic cleaver, and then put the cleaned and flat end faces of the HST and the cut dislocation structure into the fiber optic fusion splicer respectively, and close the clamp to prevent the SMF and HST from loosening; S5. Set the discharge parameters of the optical fiber fusion splicer to discharge and fusion-splice the SMF and HST; S6. Open the fixture, move the HST under the optical moving platform, cut the HST to a length of 1050μm, put the cut HST section into one end of the fusion splicer, take another section of SMF to remove 3cm of the coating layer, wipe it clean with cotton dipped in alcohol, and then use a fiber optic cutting knife to cut the end face of the other section of SMF flat and put it into the other end of the fusion splicer, adjust the motor of the fiber optic fusion splicer to place the two end faces in the center of the display panel of the fiber optic fusion splicer, set the appropriate parameters and discharge to form an air cavity to make the fiber optic structure.

[0008] A fiber optic structure capable of simultaneously measuring curvature and temperature, the structure comprising an SMF (single-mode fiber) and an HST (fiber optic adapter). A misaligned structure is formed at the connection between the SMF and the HST with the central axis of the SMF, the misaligned distance is 4 μm, the distance of the misaligned SMF portion is 300 μm, the SMF of the misaligned portion is connected to the HST, the length of the HST is 1050 μm, to form a fiber optic structure.

[0009] A fiber optic system capable of simultaneously measuring curvature and temperature, the system comprising a fiber optic structure capable of simultaneously measuring curvature and temperature, the system also comprising a light source (BBS), a fiber optic amplifier (TDAF), a rapid temperature change test chamber (TC) and an optical spectrum analyzer (OSA), the light source connecting the fiber optic amplifier, the displacement platform and the fiber optic structure, the fiber optic structure connecting the rapid temperature change test chamber and the optical spectrum analyzer; the system can be used to simultaneously measure curvature and temperature.

[0010] The beneficial effects of the present invention are: By demodulating the temperature-sensitive MZI wavelength and the antiresonance intensity that is sensitive to curvature, the cross-sensitivity problem between curvature and temperature is solved. The present invention adopts a solution of measuring curvature and temperature simultaneously to reduce the crosstalk from temperature in curvature measurement, and the sensor probe has a simple structure, stable performance and low price. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a flow chart of a method for making an optical fiber structure; Figure 2 is a schematic diagram of the optical fiber structure; Figure 3 Schematic diagram of HST optical path in a bent state; Figure 4 It is the schematic diagram of the unique sensing experimental system; Figure 5 Schematic diagram of the temperature sensing experimental device. DETAILED DESCRIPTION

[0012] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0013] See also Figure 1 , provides a method for manufacturing an optical fiber structure capable of simultaneously measuring curvature and temperature, the method comprising the steps of: S1. Use fiber pliers to strip the coating of the two SMF ends, about 2 cm long each, wipe them clean with cotton dipped in alcohol, cut the ends flat with a fiber cleaver, then put the two SMFs with the coating stripped off into the fiber fusion splicer and close the clamp; S2. Move the motor to adjust the relative position of the two optical fiber end faces by 4 μm, set the discharge parameters of the optical fiber fusion splicer, and discharge to make the SMF end faces staggered and fused; S3. Place the welded structure on the displacement platform and cut it off at 300 μm away from the dislocated structure; S4. Use fiber optic pliers to peel off the HST coating layer, about 1.5 cm in length, wipe it clean with cotton dipped in alcohol, cut the end face flat with a fiber cleaver, and then put the HST with a flat end face and the dislocation structure that has been cut into the fiber fusion splicer respectively, and close the clamp to prevent the SMF and HST from loosening; S5. Set the discharge parameters of the optical fiber fusion splicer to discharge and fusion-splice the SMF and HST; S6. Open the fixture, move the HST under the optical moving platform, cut the HST to a length of 1050μm, put the cut HST section into one end of the fusion splicer, take another section of SMF to remove 3cm of the coating layer, wipe it clean with cotton dipped in alcohol, and then use a fiber optic cutter to cut the end face flat and put it into the other end of the fusion splicer, adjust the motor of the fiber optic fusion splicer to place the two end faces in the center of the display panel of the fiber optic fusion splicer, set the appropriate parameters and discharge to form an air cavity to make the fiber optic structure.

[0014] See also Figure 2 , provides an optical fiber structure that can simultaneously measure curvature and temperature, the structure includes SMF (single-mode optical fiber) and HST (optical fiber adapter), the connection between the SMF and the HST forms a staggered structure with the central axis of the SMF, the staggered distance is 4μm, the distance of the staggered SMF part is 300μm, the SMF of the staggered part is connected to the HST, the length of the HST is 1050μm, forming an optical fiber structure.

[0015] When light enters the dislocation structure, high-order cladding modes are excited due to mode field mismatch. The core mode and cladding mode continue to propagate within the HST until they leave another dislocation structure. The incident beam is combined and part of the excited cladding mode is coupled back to the core of the SMF. Due to the optical phase difference between the core mode and the excited cladding mode, a typical MZI is formed. The interference intensity and phase difference of the MZI can be expressed as follows: ; ; in and are the light intensities of the core mode and the higher-order cladding mode, respectively; is the wavelength in vacuum; L1 and L2 are the lengths of the SMF and HST associated with the interference, respectively; and are the RI of air and silica, respectively; It is the phase difference between the two interfering lights: LOPD is the optical path difference between the core mode and the higher-order cladding mode.

[0016] When the phase difference satisfies the condition , That is: ; Interference trough appears, where m is an integer, is the wavelength of the mth order interference fringe.

[0017] When the external temperature or curvature changes, the effective interference refractive index and effective length of the interferometer will change, causing the optical phase difference between the core mode and the higher-order mode to change, so the MZI fringes will move.

[0018] An anti-resonant reflection effect will occur at the HST. For the anti-resonant reflection effect, the resonant wavelength λ can be expressed by the cladding thickness d as follows:

[0019] Here, m is a positive integer representing the number of resonance orders, is the refractive index of silicon dioxide, and the intensity of the transmission fringe can be expressed as:

[0020] in, is the intensity of the incident light at the resonant wavelength.

[0021] See also Figure 3 , in the case of changing curvature, the HST is compressed on one side and stretched on the other side, which has two consequences. On the one hand, the core mode and cladding mode propagate asymmetrically around the HST. Therefore, the length of the MZ interference is different under different bending conditions. Therefore, the wavelength of the MZI moves with the change of curvature. On the other hand, when the curvature changes, the symmetry of the interference beam around the HST is destroyed: the optical path of the interference beam on the stretched side increases, while the optical path of the interference beam on the compressed side decreases. Considering that the incident angle of the guided light is finite, the light intensity at the resonant wavelength changes with the increase of the curvature. The optical path inside the HST in the bent state is as follows: Figure 2 shown.

[0022] Sensing characteristics test system: See also Figure 4 In the curvature sensing experiment, the input and output ends of the optical fiber structure of this embodiment are connected to TDFA, and the two ends of TDFA are connected to the light source (BBS) and the optical spectrum analyzer (OSA) respectively. The optical fiber structure is fixed on the TDAF (here is the displacement platform), and the curvature of the optical fiber structure is changed by adjusting the displacement platform. The initial reflection spectrum is recorded when the displacement is 0μm. When the displacement increases by 200μm each time, the relationship between the curvature and the displacement is: ; Where, L = 18.5 cm, R = radius of curvature, and d is the displacement of the translation stage.

[0023] See also Figure 5In the temperature sensing experiment, the two ends of the optical fiber structure were connected to BBS and OSA respectively, and the optical fiber structure was fixed with a glass sheet and placed in a temperature control box (TC). The temperature of the temperature control box was adjusted to record the response of the optical fiber structure to temperature. The initial reflection spectrum was recorded at 30°C, and it was recorded every 10°C from 20°C to 90°C for a total of 7 times.

[0024] By combining the above device with the optical fiber structure of this embodiment: the curvature sensing experimental device and the temperature sensing experimental device, the cross sensitivity problem of curvature and temperature is solved by demodulating the temperature-sensitive MZI wavelength and the anti-resonance intensity to be sensitive to curvature. The present invention adopts a solution of measuring curvature and temperature simultaneously to reduce the crosstalk from temperature in curvature measurement, and the optical fiber structure of this embodiment has a simple structure, stable performance and low price.

[0025] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for manufacturing an optical fiber structure capable of simultaneously measuring curvature and temperature, characterized in that: The method steps include: S1. Use fiber pliers to strip the coating of the two ends of the two SMFs, with a length of 0-2 cm each, wipe them clean with cotton dipped in alcohol, use a fiber cleaver to cut the two ends of the two SMFs evenly, then put the two SMFs with the coating stripped off into the fiber fusion splicer and close the clamp; S2. Move the motor to adjust the position distance between the two end faces of the two SMF segments to 4 μm, set the discharge parameters of the optical fiber fusion splicer, and discharge to make the two end faces of the two SMF segments to be staggered and fused; S3. Place the welded structure on the displacement platform and cut it off at 300 μm away from the dislocated structure; S4. Use fiber optic pliers to peel off the HST coating layer, the length of which is in the range of 0-1.5cm, wipe it clean with cotton dipped in alcohol, cut the two end faces of the HST flat with a fiber optic cleaver, and then put the cleaned and flat end faces of the HST and the cut dislocation structure into the fiber optic fusion splicer respectively, and close the clamp to prevent the SMF and HST from loosening; S5. Set the discharge parameters of the optical fiber fusion splicer to discharge and fusion-splice the SMF and HST; S6. Open the fixture, move the HST under the optical moving platform, cut the HST to a length of 1050μm, put the cut HST section into one end of the fusion splicer, take another section of SMF to remove 3cm of the coating layer, wipe it clean with cotton dipped in alcohol, and then use a fiber optic cutting knife to cut the end face of the other section of SMF flat and put it into the other end of the fusion splicer, adjust the motor of the fiber optic fusion splicer to place the two end faces in the center of the display panel of the fiber optic fusion splicer, set the appropriate parameters and discharge to form an air cavity to make the fiber optic structure.

2. An optical fiber structure capable of simultaneously measuring curvature and temperature, characterized in that: The optical fiber structure includes SMF and HST. The connection between the SMF and HST forms a staggered structure with the central axis of the SMF. The staggered distance is 4μm. The distance of the staggered SMF part is 300μm. The SMF of the staggered part is connected to the HST. The length of the HST is 1050μm to form an optical fiber structure.

3. An optical fiber system capable of simultaneously measuring curvature and temperature, the system comprising the optical fiber structure capable of simultaneously measuring curvature and temperature as claimed in claim 2, characterized in that: The system also includes a light source, an optical fiber amplifier, a displacement platform, a rapid temperature change test box and a spectrum analyzer; the light source is connected to the optical fiber amplifier, the displacement platform and the optical fiber structure, and the optical fiber structure is connected to the rapid temperature change test box and the optical skin analyzer; the system can be used to simultaneously measure curvature and temperature.

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