All-silica fiber Fabry-Perot sensor and manufacturing method thereof

Abstract

The invention discloses an all-silica optical fiber Fabry-Perot sensor and a manufacturing method. The sensor is composed of a silica optical fiber, a quartz tube, a reflector, an optical fiber tail cable and an optical fiber connector. Wherein the core structure quartz optical fiber, the quartz tube and the reflector are all made of quartz materials, and the quartz optical fiber and the quartz tube are connected through laser welding to form a full-quartz structure, so that maximum thermal expansion coefficient matching is realized, the packaging internal stress of the sensor is reduced, and the working temperature upper limit and the measurement precision are improved. According to the optical fiber sensor, Fabry-Perot interference is formed through reflected light of the end face of the optical fiber and the end face of the reflector, the optical fiber temperature, strain and pressure sensor of a full-quartz structure can be formed by replacing the reflector and changing the connection relation between the reflector and the quartz tube, and the universality is high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical fiber sensing, and particularly relates to a Fabry-Perot interferometric optical fiber sensor. BACKGROUND

[0002] The optical fiber EFPI sensor is widely used for monitoring parameters such as temperature, strain, pressure and vibration, and is a typical representative product of optical fiber sensing technology, and plays an important role in fields such as aerospace, aviation, ocean, geology and medical health.

[0003] Traditional optical fiber sensors mainly include distributed optical fiber sensors, optical fiber grating sensors and optical fiber Fabry-Perot sensors, among which the distributed optical fiber sensors and the optical fiber grating sensors are more widely used in engineering applications. This is because in the process of engineering application of the optical fiber Fabry-Perot sensor, researchers have found a series of problems that restrict the engineering application, such as poor environmental adaptability, low measurement accuracy and difficult installation. The main reasons for low measurement accuracy include poor sensor consistency, obvious internal stress under high temperature, large demodulation error, etc. If the influence of internal stress under high temperature on the measurement result can be effectively optimized, the measurement accuracy can be effectively improved, and the further development of the optical fiber Fabry-Perot sensor can be promoted. SUMMARY

[0004] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a full-quartz optical fiber Fabry-Perot sensor and a manufacturing method. The method uses a full-quartz assembly and a glue-free packaging method, which can effectively reduce the internal stress introduced during assembly, thereby improving the measurement accuracy. Moreover, the method is universal, and by increasing and adjusting the structure, a full-quartz optical fiber Fabry-Perot strain sensor, a temperature sensor and a pressure sensor can be realized respectively.

[0005] The technical solution of the present application is as follows: a full-quartz optical fiber Fabry-Perot sensor, comprising a quartz optical fiber, a quartz tube, a reflector, an optical fiber tail cable and an optical fiber joint.

[0006] The quartz optical fiber and the reflector are vertically placed, so that the end face of the optical fiber and the end face of the reflector are parallel to each other and form a Fabry-Perot interference. The quartz tube is used to support and fix the quartz optical fiber. The optical fiber tail cable is used to transmit optical signals, and the end is an optical fiber joint, which is convenient for connecting the sensor with a signal demodulation device.

[0007] When the quartz tube and the reflector are independent of each other, they can be used for strain measurement; when the quartz tube and the reflector are connected as a whole, they can be used for temperature or pressure measurement.

[0008] The quartz optical fiber is removed from the coating layer, and the quartz cladding is connected with the quartz tube, and the connection mode adopts laser fusion.

[0009] The quartz optical fiber needs to transmit and reflect light, and the end face close to the reflector is processed by fiber cutting and grinding and other processes.

[0010] The reflector is a solid quartz cylinder, and the end face close to the optical fiber should have light reflecting ability.

[0011] The optical fiber tail cable can be armored by carbon fiber tube, metal threaded tube and the like, which can effectively improve the overall temperature resistance of the sensor.

[0012] The optical fiber connector is used to connect with other demodulation equipment, and FC connector or LC connector is selected.

[0013] A full quartz optical fiber Fabry-Perot sensor manufacturing method, the manufacturing steps are as follows: 1) cut the quartz optical fiber to the appropriate length, remove a part of the coating layer at one end (marked as A), and cut the optical fiber with a fiber cutting knife to obtain a good fiber end face; 2) insert the A end of the quartz optical fiber into the quartz tube, and the end face of the quartz optical fiber is basically flush with the end face of the quartz tube; 3) fuse the quartz optical fiber and the quartz tube together by a fiber fusion machine; 4) cut the metal threaded tube to the appropriate length to armor the optical fiber tail cable; 5) use the standard process of fiber connector manufacturing and grinding to manufacture the fiber connector at the other end of the quartz optical fiber.

[0014] The sensor manufactured by the above steps can be used as a full quartz optical fiber Fabry-Perot strain sensor for strain monitoring. If a full quartz optical fiber Fabry-Perot temperature or pressure sensor is manufactured, the quartz tube and the reflector need to be fixed together by a connecting structure, and the relative distance between the quartz tube and the reflector is adjusted. At the same time, the reflector of the full quartz optical fiber Fabry-Perot pressure sensor usually selects a solid quartz cylinder with a thickness less than 100 μm.

[0015] Compared with the prior art, the present application has the following beneficial effects: 1) The existing optical fiber Fabry-Perot sensor usually uses metal or ceramic structure for optical fiber packaging. Due to the large difference in thermal expansion coefficient between metal and ceramic materials and quartz, when the external temperature changes, a large internal stress will be generated, which may introduce measurement error, or even cause component connection failure, optical fiber fracture and other problems. This phenomenon is particularly evident at high temperatures. The core components of the present application are made of quartz material, which is consistent with the quartz optical fiber, effectively avoiding the problems caused by the difference in thermal expansion coefficient, and is beneficial to improve the upper limit of the working temperature of the sensor and the measurement accuracy.

[0016] 2) The traditional fiber-optic Fabry-Perot sensor is usually fixed by means of adhesive bonding between components. On the one hand, the bonding position and bonding area are difficult to unify, resulting in inconsistent internal stress and temperature sensitivity of the sensor. On the other hand, the temperature resistance, bonding strength, and moisture resistance of the adhesive need to be considered to avoid problems such as adhesive falling off and failure. The present application uses laser welding to realize glue-free packaging between quartz, which can accurately position the bonding position, has a simple process, and a firm and reliable fixing method. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a full quartz fiber-optic Fabry-Perot sensor structure schematic diagram; Figure 2 is a sensor sensing principle schematic diagram; Figure 3 is a full quartz fiber-optic Fabry-Perot strain sensor structure schematic diagram; Figure 4 is a full quartz fiber-optic Fabry-Perot temperature sensor structure schematic diagram; Figure 5 is a full quartz fiber-optic Fabry-Perot pressure sensor structure schematic diagram. DETAILED DESCRIPTION

[0018] The present application relates to a full quartz fiber-optic Fabry-Perot sensor, comprising a quartz optical fiber 1, a quartz tube 2, a reflector 3, an optical fiber tail cable 4, and an optical fiber joint 5; The quartz optical fiber 1 and the reflector 3 are vertically placed, so that the fiber end face of the quartz optical fiber 1 and the end face of the reflector 3 are parallel to each other and form a Fabry-Perot interference; one end of the quartz tube 2 is connected to the quartz optical fiber 1 for supporting and fixing the quartz optical fiber 1; the other end of the quartz tube 2 is connected to one end of the optical fiber tail cable 4 for transmitting optical signals; the other end of the optical fiber tail cable 4 is connected to the optical fiber joint 5 for connecting the sensor to an external signal demodulation device.

[0019] When the quartz tube 2 and the reflector 3 are independent of each other, they can be used for strain measurement; when the quartz tube 2 and the reflector 3 are connected as a whole, they can be used for temperature or pressure measurement.

[0020] After removing the coating layer of the quartz optical fiber 1, the quartz cladding is connected to the quartz tube 2, and the connection method uses laser welding.

[0021] The quartz optical fiber 1 is processed by fiber cutting and grinding to make the end face close to the reflector 3 have light reflection capability.

[0022] The reflector 3 is a solid quartz cylinder, and the end face close to the quartz optical fiber 1 has light reflection capability.

[0023] The optical fiber tail cable 4 is armored with a carbon fiber tube or a metal threaded tube.

[0024] The optical fiber joint 5 adopts an FC joint or an LC joint.

[0025] A method for manufacturing the all-quartz optical fiber Fabry-Perot sensor, characterized in that the method comprises the following steps: The quartz optical fiber 1 is cut, the coating layer at one end A of the quartz optical fiber 1 is removed, and the optical fiber end face is cut by using an optical fiber cutting knife or is polished by using an optical fiber polishing process. The end A of the quartz optical fiber 1 is inserted into the quartz tube 2, and the end face of the quartz optical fiber 1 is flush with the end face of the quartz tube 2. The quartz optical fiber 1 and the quartz tube 2 are fused together by using an optical fiber fusion machine. The metal threaded tube is used to armor the optical fiber tail cable 4. The optical fiber joint 5 is manufactured at the other end of the quartz optical fiber 1 by using a standard optical fiber joint manufacturing and polishing process.

[0026] If the all-quartz optical fiber Fabry-Perot temperature or pressure sensor is manufactured, the quartz tube 2 and the reflector 3 are fixed together by using a connecting structure, and the relative distance between the quartz tube 2 and the reflector 3 is adjusted, and meanwhile, the thickness of the solid quartz cylinder of the reflector 3 of the all-quartz optical fiber Fabry-Perot pressure sensor is less than 100 μm.

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below by combining with specific embodiments and referring to the drawings.

[0028] The all-quartz optical fiber Fabry-Perot sensor provided by the present application is shown in Figure 1 The sensor is based on the F-P interference principle, and the end face of the optical fiber and the end face of the reflector are used as the reflecting surfaces respectively to form an EFPI cavity, and the EFPI cavity length change is used to perceive the change of the external physical parameter, as shown in Figure 2 The other end of the optical fiber is manufactured into an optical fiber joint, which can be directly connected with a signal demodulation device. The whole sensor can be used to realize the strain, temperature, pressure signal perception and signal transmission, as shown in Figure 3 、 Figure 4 、 Figure 5

[0029] Embodiment 1 In this embodiment, an all-quartz optical fiber Fabry-Perot sensor which can be used in an environment below 800℃ is manufactured. In order to meet the use requirements, the gold-coated single-mode optical fiber with a cladding diameter of 125 μm is selected. The armored structure selects a metal threaded tube with an outer diameter of 3 mm. The manufacturing steps of the optical fiber Fabry-Perot sensor are as follows.

[0030] 1) A gold-coated optical fiber with a length of about 1 m is cut, the coating layer at one end (marked as A) is removed by about 20 mm, and the optical fiber is cut by using an optical fiber cutting knife to obtain a flat optical fiber end face. ​

[0031] 2) Insert the A end of the gold-coated optical fiber into a quartz tube with an inner diameter of 126μm and an outer diameter of 2mm. The A end face of the gold-coated optical fiber is basically flush with the end face of the quartz tube.

[0032] 3) The LZM-125A+ fiber optic fusion splicing workstation was selected to fuse the gold-coated optical fiber and the quartz tube together through focusing and discharge.

[0033] 4) Cut a metal threaded tube about 0.95m in length, and put the metal threaded tube on the optical fiber pigtail to armor the optical fiber.

[0034] 5) Assemble the fiber optic connector at the other end of the quartz fiber (denoted as B), and complete the fiber optic connector polishing process according to the FC / APC connector standard polishing process.

[0035] If an all-fiber Fabry-Perot strain sensor is to be fabricated, such as Figure 3 As shown. Place the reflector in front of the A end of the gold-coated fiber, so that the A end face and the reflector end face are parallel to each other, and adjust the relative distance between the A end face and the reflector end face to be between 200 and 500 μm.

[0036] If a full-fiber Fabry-Perot temperature sensor is to be fabricated, such as Figure 4 As shown. The quartz tube and the reflector are connected together by a connecting structure, and the relative distance between the quartz tube and the reflector is adjusted so that the relative distance between end face A and end face of the reflector is between 200 and 500 μm. Then, the connecting structure and the quartz tube, and the connecting structure and the reflector are fused together by the fiber optic fusion splicing workstation LZM-125A+.

[0037] To fabricate an all-fiber Fabry-Perot pressure sensor, a solid quartz cylinder with a thickness of 50 μm is chosen as the reflector, such as... Figure 5 As shown. The quartz tube and the reflector are connected together by a connecting structure, and the relative distance between the quartz tube and the reflector is adjusted so that the relative distance between end face A and end face of the reflector is between 200 and 500 μm. Then, the connecting structure and the quartz tube, and the connecting structure and the reflector are fused together by the fiber optic fusion splicing workstation LZM-125A+.

[0038] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fully quartz fiber optic Fabry-Perot sensor, characterized in that: Includes quartz optical fiber (1), quartz tube (2), reflector (3), optical fiber pigtail (4) and optical fiber connector (5); The quartz fiber (1) and the reflector (3) are placed vertically, so that the fiber end face of the quartz fiber (1) and the end face of the reflector (3) are parallel to each other and form a Fabry-Perot interference; one end of the quartz tube (2) is connected to the quartz fiber (1) to support and fix the quartz fiber (1); the other end of the quartz tube (2) is connected to one end of the fiber optic pigtail (4) used to transmit optical signals; the other end of the fiber optic pigtail (4) is connected to the fiber optic connector (5) used to connect the sensor to the external signal demodulation equipment.

2. The all-quartz fiber optic Fabry-Perot sensor according to claim 1, characterized in that: When the quartz tube (2) and the reflector (3) are independent of each other, they can be used for strain measurement; when the quartz tube (2) and the reflector (3) are connected as a whole, they can be used for temperature or pressure measurement.

3. The all-quartz fiber optic Fabry-Perot sensor according to claim 1, characterized in that: After the coating layer is removed from the quartz optical fiber (1), it is connected to the quartz tube (2) by means of quartz cladding and laser fusion splicing.

4. The all-quartz fiber optic Fabry-Perot sensor according to claim 1, characterized in that: The quartz optical fiber (1) is made to have light reflection capability at the end face near the reflector (3) through optical fiber cutting and grinding processes.

5. The all-quartz fiber optic Fabry-Perot sensor according to claim 1, characterized in that: The reflector (3) is a solid quartz cylinder, and its end face near the quartz optical fiber (1) has light reflection capability.

6. The all-quartz fiber optic Fabry-Perot sensor according to claim 1, characterized in that: The fiber optic pigtail (4) is armored with carbon fiber tubes or metal threaded tubes.

7. The all-quartz fiber optic Fabry-Perot sensor according to claim 1, characterized in that: The fiber optic connector (5) is either an FC connector or an LC connector.

8. A method for fabricating the all-quartz fiber optic Fabry-Perot sensor of claim 1, characterized in that, include: Cut a quartz optical fiber (1), remove a section of coating layer from one end A, and cut the fiber end face using an optical fiber cleaver, or complete the fiber end face grinding process. Insert the A end of the quartz optical fiber (1) into the quartz tube (2) and ensure that the end face of the quartz optical fiber (1) is flush with the end face of the quartz tube (2). The quartz optical fiber (1) and the quartz tube (2) are fused together using an optical fiber fusion splicer; Cut a metal threaded tube to armor the fiber optic pigtail (4); Using standard processes for fiber optic connector fabrication and polishing, fiber optic connector (5) is fabricated at the other end of the quartz fiber (1).

9. The manufacturing method according to claim 8, characterized in that, If a full quartz fiber optic Fabry-Perot temperature or pressure sensor is to be made, a connecting structure is used to fix the quartz tube (2) and the reflector (3) together, and the relative distance between the quartz tube (2) and the reflector (3) is adjusted. Meanwhile, the reflector (3) of the full quartz fiber optic Fabry-Perot pressure sensor is a solid quartz cylinder with a thickness of less than 100 μm.

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