Heatable sleeve for reducing low-temperature loss at optical fiber welding part in vacuum Dewar

Abstract

The invention provides a heatable sleeve for reducing low temperature loss at a fiber welding position in a vacuum Dewar, which comprises a ceramic sleeve, a heating ring, an adjustable support device and a control system, and is characterized in that a fiber, the ceramic sleeve and the heating ring are sequentially sleeved from inside to outside, heat conduction mud is arranged in the ceramic sleeve, the welding position of the fiber is embedded in the heat conduction mud, and the adjustable support device is arranged in the heat conduction mud. The ceramic sleeve is fixedly installed in the Dewar through an adjustable supporting device, a temperature sensor is arranged on the outer side of the heat shrink tube at the welding position of the optical fiber, and the temperature sensor and the heating ring are electrically connected with a control system. According to the invention, heat input is adjusted through the electric heating ring, heat conduction is carried out through the ceramic sleeve to heat the fusion welding part of the optical fiber, and heat generated by the heating ring is uniformly conducted to the fusion welding part of the optical fiber through the ceramic sleeve and the plastic low-temperature heat conduction mud, so that the temperature of the fusion welding part is kept in a normal temperature area; therefore, stress concentration and signal transmission loss caused by profound hypothermia are reduced, and good sensing characteristics of the optical fiber are ensured.

Description

Technical Field

[0001] The invention relates to the field of optical fiber technology, in particular to a heatable sleeve for reducing low-temperature loss at an optical fiber fusion splice in a vacuum dewar. Background Art

[0002] Optical fiber technology is widely used in scientific research, aerospace, energy industry, medicine, quantum information and polar exploration due to its advantages of anti-electromagnetic interference, strong insulation and flexibility in deep cryogenic environments. In low-temperature physics experiments, superconducting quench detection, liquid fuel monitoring and quantum communications, optical fiber sensors are used to accurately measure key parameters such as temperature, strain and pressure.

[0003] However, the deep cryogenic environment will increase the transmission loss of optical signals in the optical fiber to a certain extent. The thermal expansion coefficient of the optical fiber at the fusion joint in the deep cryogenic environment is different from that of other parts, which easily leads to stress concentration during the cooling process, resulting in a sharp attenuation of the optical signal and a significant decrease in detection sensitivity. Therefore, in the deep cryogenic environment, the low temperature loss at the optical fiber fusion joint becomes an important factor affecting the feasibility and accuracy of optical fiber parameter detection.

[0004] At present, although traditional optical fiber protection methods such as heat shrink tubing can provide certain mechanical strength and environmental protection, they often cannot solve the problem of excessive loss at the fusion joint under deep cryogenic conditions. Therefore, it is urgent to explore a technology that can reduce the deep cryogenic loss at the optical fiber fusion joint to ensure the stability of optical fiber signal transmission under deep cryogenic conditions.

[0005] After searching, the patent with publication number CN219676327U proposed a method for heating and shaping the optical fiber fusion tube, but it only solved the problem of heating and shaping the optical fiber fusion joint, and did not consider the loss of the optical fiber fusion joint in the deep low temperature vacuum dewar. The patent with publication number CN217213235U proposed a method of using a cement mortar layer to improve the mechanical strength of the optical fiber fusion joint, but it only solved the problem of mechanical strength of the fusion joint, and did not consider the problem of greatly increased fusion loss of optical fiber in a deep low temperature vacuum environment.

[0006] The traditional fiber fusion splicing method has losses at the fusion point, especially when the temperature drops below the liquid nitrogen temperature zone, the fiber loss is particularly obvious, seriously affecting the sensing characteristics of the fiber. Therefore, how to solve the loss at the fiber fusion splice under the deep low temperature of the vacuum Dewar is a technical problem in the application of fiber optic sensing detection technology in the deep low temperature environment of the vacuum Dewar.

[0007] In view of the above problems, it is necessary to propose a heatable sleeve for reducing the deep cryogenic loss at the optical fiber fusion splice in a vacuum dewar, ensuring that the optical fiber fusion splice remains in the normal temperature zone, thereby reducing the signal transmission loss of the optical fiber in the deep cryogenic environment, and ensuring the sensitivity and accuracy of the optical fiber sensor in parameter detection in the deep cryogenic environment. Summary of the invention

[0008] In view of the defects in the prior art, the object of the present invention is to provide a heatable sleeve for reducing the low temperature loss at the optical fiber fusion splice in a vacuum Dewar.

[0009] According to the present invention, a heatable sleeve for reducing low-temperature loss at the optical fiber fusion joint in a vacuum dewar comprises: a ceramic sleeve, a heating ring, an adjustable support device and a control system. The optical fiber, the ceramic sleeve and the heating ring are sequentially sleeved from the inside to the outside. A thermal conductive mud is arranged inside the ceramic sleeve. The fusion joint of the optical fiber is embedded in the thermal conductive mud. The ceramic sleeve is fastened and installed in the dewar through the adjustable support device. A temperature sensor is arranged on the outside of the heat shrink tube at the fusion joint of the optical fiber. The temperature sensor and the heating ring are electrically connected to the control system respectively.

[0010] Preferably, the heating coil is movably mounted on the outside of the ceramic sleeve, and the inner wall of the heating coil is slidably matched with the outer wall of the ceramic sleeve.

[0011] Preferably, the length of the ceramic sleeve is greater than the length of the heat shrink tube at the fusion joint of the optical fiber.

[0012] Preferably, the length of the heating coil is shorter than the length of the ceramic sleeve and longer than the length of the fusion joint of the optical fiber.

[0013] Preferably, the heating coil comprises a resistive cylindrical heating coil.

[0014] Preferably, the temperature sensor is arranged in close contact with the heat shrink tube.

[0015] Preferably, the adjustable supporting device comprises a middle circular ring and an outer adjusting device, the inner diameter of the circular ring can be expanded or reduced by adjusting the adjusting device, and the ceramic sleeve is clamped and connected inside the circular ring.

[0016] Preferably, the adjusting device comprises a plurality of parallel connecting rods, the adjustable supporting device is fastened to the Dewar via the connecting rods, the connecting rods are arranged parallel to the optical fiber, and the optical fiber is always in a straight state.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention adjusts the heat input through the electric heating ring, and heats the fusion joint of the optical fiber through the ceramic sleeve for heat conduction. The heat generated by the heating ring is evenly conducted to the fusion joint of the optical fiber through the ceramic sleeve and the plastic low-temperature thermal conductive mud, ensuring that the temperature of the fusion joint is maintained in the normal temperature range, thereby reducing the stress concentration and signal transmission loss caused by deep low temperature, thereby ensuring good sensing characteristics of the optical fiber.

[0019] 2. The present invention achieves temperature control of the optical fiber fusion joint under a deep low-temperature vacuum environment through the close cooperation of the heating ring, temperature sensor, ceramic sleeve and control system, and has a compact overall structure. It also greatly increases the mechanical strength of the optical fiber fusion joint, thereby effectively reducing the deep low-temperature loss at the optical fiber fusion joint and enhancing the detection performance of the optical fiber sensor.

[0020] 3. The present invention uses plastic thermal conductive mud inside the ceramic sleeve to make real-time adjustments according to different optical fiber models to meet the needs of different types of optical fiber fusion splicing, and the entire sleeve device can be moved up and down inside the Dewar, so the entire device can be repeatedly used to reduce the low-temperature loss of different types of optical fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0022] Figure 1 The present invention mainly embodies the structural schematic diagram of a heatable sleeve for reducing low-temperature loss at the optical fiber fusion splicing in a vacuum Dewar;

[0023] Figure 2 The present invention mainly embodies a transverse cross-sectional view of a heatable sleeve for reducing low-temperature loss at an optical fiber fusion splice in a vacuum Dewar.

[0024] As shown in the figure:

[0025] Optical fiber 1 Heat shrink tube 2 Thermal paste 3

[0026] Ceramic sleeve 4 Heating ring 5 Adjustable support device 6

[0027] Temperature sensor 7 DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0029] like Figure 1 and2 As shown, a heatable sleeve for reducing the low-temperature loss at the optical fiber fusion joint in a vacuum dewar according to the present invention comprises: a ceramic sleeve 4, a heating ring 5, an adjustable supporting device 6 and a control system. The optical fiber 1, the ceramic sleeve 4 and the heating ring 5 are sequentially sleeved from the inside to the outside. A thermal conductive mud 3 is arranged inside the ceramic sleeve 4. The fusion joint of the optical fiber 1 is embedded in the thermal conductive mud 3. The ceramic sleeve 4 is fastened and installed in the dewar through the adjustable supporting device 6. A temperature sensor 7 is arranged on the outside of the heat shrink tube 2 at the fusion joint of the optical fiber 1. The temperature sensor 7 and the heating ring 5 are electrically connected to the control system respectively.

[0030] In the relevant experiments in the field of deep low temperature optical fiber temperature measurement, it is usually necessary to carry out in a closed vacuum dewar to achieve a vacuum deep low temperature state. The optical fiber in the dewar is connected to the monitoring equipment outside the dewar through a vacuum optical fiber flange. In order to obtain accurate data and ensure the integrity of signal transmission, it is necessary to weld the monitoring optical fiber in the dewar and the jumper of the optical fiber flange, so the welding point needs to be placed in the monitoring environment in the closed dewar. The optical fiber welding point causes obvious loss of optical signal due to material density, local stress and refractive index changes, which affects the sensing performance and even causes data distortion, thereby reducing the measurement accuracy and stability of the experiment. In the deep low temperature environment of the vacuum dewar, the optical fiber welding point is prone to loss. The present application adopts an electric heating ring 5 to adjust the heat control by current and then conduct heat through the ceramic sleeve 4 to heat the welding point of the optical fiber 1. The heat generated by the heating ring 5 is evenly conducted to the welding point of the optical fiber 1 through the ceramic sleeve 4 and the plastic low temperature thermal conductive mud 3, ensuring that the temperature of the welding point is kept in the normal temperature range, thereby reducing the stress concentration and signal transmission loss caused by deep low temperature, thereby ensuring the good sensing characteristics of the optical fiber.

[0031] The heating coil 5 is movably mounted on the outside of the ceramic sleeve 4 , and the inner wall of the heating coil 5 is slidably matched with the outer wall of the ceramic sleeve 4 , that is, the heating coil 5 can slide smoothly on the outside of the ceramic sleeve 4 .

[0032] The length of the ceramic sleeve 4 is greater than the length of the heat shrink tube 2 at the fusion joint of the optical fiber 1. The length of the ceramic sleeve 4 should be greater than the fusion joint position of the optical fiber 1 to ensure the mechanical strength of the optical fiber 1. The ceramic sleeve 4 and the plastic low-temperature thermal conductive mud 3 play a dual role of heat conduction and mechanical protection. The thermal conductive mud 3 ensures that the heat of the heating ring 5 can be efficiently transferred to the fusion joint of the optical fiber 1, while preventing the ceramic sleeve 4 from directly applying mechanical pressure to the optical fiber 1, reducing the influence of stress on the optical fiber sensing. This design can ensure the good transmission performance of the optical fiber 1 under deep low temperature conditions, while providing the necessary mechanical support and protection for the optical fiber 1.

[0033] The length of the heating coil 5 is shorter than the ceramic sleeve 4 and longer than the length of the fusion joint of the optical fiber 1. The heating coil 5 is shorter than the ceramic sleeve 4 and slightly longer than the heat shrink tube of the optical fiber fusion joint, in order to accurately control the heat applied to the fusion joint.

[0034] The heating coil 5 comprises a cylindrical heating coil of a resistance type.

[0035] The temperature sensor 7 is attached to the heat shrink tube 2. The temperature sensor 7 is used to monitor the temperature of the fusion joint of the optical fiber 1 in real time, and the heating power of the heating coil 5 is manually adjusted according to the temperature displayed by the temperature sensor 7 to ensure that the fusion joint is stable in the normal temperature range. Through this closed-loop control mechanism, the increase in loss caused by deep low temperature can be avoided, thereby maintaining the high sensitivity of the optical fiber 1 and the stability of signal transmission.

[0036] The adjustable support device 6 includes a middle circular ring and an outer adjusting device. The inner diameter of the circular ring can be enlarged or reduced by adjusting the adjusting device, and the ceramic sleeve 4 is clamped and connected inside the circular ring. The adjusting device includes a plurality of parallel connecting rods, and a connecting piece is provided on the circumferential side of the circular ring and is movably connected to the connecting rod, so that the circular ring can move along the axial direction of the connecting rod on the connecting rod, so as to be applicable to the position of various ceramic sleeves 4. The adjustable support device 6 is tightly connected to the Dewar through the connecting rod, and the connecting rod is arranged parallel to the optical fiber 1, and the optical fiber 1 is always in a straight state. The adjustable support device 6 uses a circular ring structure with an adjustable radius, and the radius of the middle circular ring is changed so that it just clamps the ceramic sleeve 4, so as to achieve the effect of limiting the device here. The optical fiber 1 can always be in a straight state to avoid the loss caused by the bending of the optical fiber 1 and affect the test.

[0037] The overall structural design of the present application is compact. Through the close cooperation of the heating coil 5, the temperature sensor 7, the ceramic sleeve 4 and the control system, the temperature control of the fusion splice of the optical fiber 1 in a deep low-temperature vacuum environment is achieved, and the mechanical strength of the fusion splice of the optical fiber 1 is greatly increased, thereby effectively reducing the deep low-temperature loss at the fusion splice of the optical fiber 1 and enhancing the detection performance of the optical fiber sensor.

[0038] The method of using the present application is as follows: First, the fusion joint of the optical fiber sensor is embedded in the plastic heat-conducting mud 3 inside the ceramic sleeve 4, and the position of the cylindrical heating ring 5 is adjusted outside it to ensure that the fusion joint of the optical fiber 1 is within the heating range of the heating ring 5; the position of the temperature sensor 7 is adjusted to fit the position of the heat shrink tube 2 of the optical fiber 1 to ensure that it can accurately monitor the temperature of the fusion joint of the optical fiber 1 in real time, and then the supporting ring is adjusted to make the whole device in a suitable position to avoid the loss caused by the bending of the optical fiber 1; the whole device is placed in a vacuum low-temperature Dewar environment, and the ambient temperature is gradually reduced to a deep low temperature, and then the heating ring 5 is started, and the power of the heating ring is manually adjusted to observe the temperature of the fusion joint, so that the temperature of the fusion joint is maintained in the normal temperature range. By recording the sensing characteristics and transmission loss of the optical fiber 1 through the optical fiber sensing system, it can be found that the sensing characteristics of the optical fiber 1 are greatly improved and the transmission loss is greatly reduced.

[0039] The heatable sleeve of the present application can ensure that the optical fiber fusion joint in a deep cryogenic vacuum dewar environment is kept in the room temperature range, minimize the deep cryogenic loss of the optical fiber, and provide stable sensing conditions for subsequent related research on optical fiber monitoring.

[0040] The present application only needs to control the current input of the heating coil 5 and observe the reading of the temperature sensor 7 to achieve real-time temperature control of the entire sleeve. The operation is simple and the temperature distribution at the fusion joint of the optical fiber 1 is uniform.

[0041] The present application can meet the needs of different types of optical fiber fusion splicing. Since the thermal conductive mud 3 inside the ceramic sleeve 4 is plastic, it can be adjusted in real time according to the different models of optical fiber 1, and the entire sleeve device can be moved up and down inside the Dewar, so the entire device can be repeatedly used to reduce the low-temperature loss of different types of optical fibers.

[0042] The adjustable supporting device 6 of the present application can be flexibly adjusted to adapt to the different positions of each fusion point, thereby avoiding the loss caused by the bending of the optical fiber 1.

[0043] The present application adjusts the local temperature of the fusion point by means of the heating coil 5, and uses the temperature sensor 7 for real-time temperature control, so that the fusion point is locally kept at a normal temperature in a deep cryogenic environment, thereby ensuring low loss at the fusion point and improving the performance of the optical fiber sensing system and the accuracy of the data. The present application effectively solves the problem of optical fiber signal loss in a deep cryogenic environment, and provides a guarantee for the reliability and effectiveness of deep cryogenic optical fiber experiments.

[0044] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0045] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A heatable sleeve for reducing low temperature loss at the optical fiber fusion splice in a vacuum Dewar, characterized in that: include: A ceramic sleeve (4), a heating coil (5), an adjustable support device (6) and a control system, wherein an optical fiber (1), the ceramic sleeve (4) and the heating coil (5) are sequentially sleeved from the inside to the outside, a heat-conducting mud (3) is arranged inside the ceramic sleeve (4), a fusion joint of the optical fiber (1) is embedded inside the heat-conducting mud (3), the ceramic sleeve (4) is fixedly installed in a dewar through the adjustable support device (6), a temperature sensor (7) is arranged outside the heat shrink tube (2) at the fusion joint of the optical fiber (1), and the temperature sensor (7) and the heating coil (5) are electrically connected to the control system respectively.

2. The heatable sleeve for reducing low temperature loss at the optical fiber fusion splice in a vacuum Dewar according to claim 1, characterized in that: The heating coil (5) is movably mounted on the outside of the ceramic sleeve (4), and the inner wall of the heating coil (5) is slidably matched with the outer wall of the ceramic sleeve (4).

3. The heatable sleeve for reducing low temperature loss at optical fiber fusion splicing in a vacuum Dewar according to claim 1, characterized in that: The length of the ceramic sleeve (4) is greater than the length of the heat shrink tube (2) at the fusion joint of the optical fiber (1).

4. The heatable sleeve for reducing low temperature loss at optical fiber fusion splicing in a vacuum Dewar according to claim 1, characterized in that: The length of the heating coil (5) is shorter than the length of the ceramic sleeve (4) and longer than the length of the fusion joint of the optical fiber (1).

5. The heatable sleeve for reducing low temperature loss at optical fiber fusion splicing in a vacuum Dewar according to claim 1, characterized in that: The heating coil (5) comprises a resistive cylindrical heating coil.

6. The heatable sleeve for reducing low temperature loss at optical fiber fusion splicing in a vacuum Dewar according to claim 1, characterized in that: The temperature sensor (7) is arranged in close contact with the heat shrink tube (2).

7. The heatable sleeve for reducing low temperature loss at optical fiber fusion splicing in a vacuum Dewar according to claim 1, characterized in that: The adjustable supporting device (6) comprises a central circular ring and an outer adjusting device. The inner diameter of the circular ring can be expanded or reduced by adjusting the adjusting device. The ceramic sleeve (4) is clamped and connected inside the circular ring.

8. The heatable sleeve for reducing low temperature loss at optical fiber fusion splicing in a vacuum Dewar according to claim 7, characterized in that: The adjustment device comprises a plurality of parallel connecting rods, the adjustable support device (6) is tightly connected to the Dewar via the connecting rods, the connecting rods are arranged parallel to the optical fiber (1), and the optical fiber (1) is always in a straight state.

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