CN117606641B - Optical fiber interference type sensor based on germanium wafer and manufacturing method thereof - Google Patents

Abstract

The invention discloses an optical fiber interference type sensor based on germanium wafer and a manufacturing method thereof, wherein the sensor comprises a single-mode fiber, a glass sleeve and the germanium wafer; the single-mode optical fiber comprises an optical fiber core positioned inside and an optical fiber cladding wrapped outside the optical fiber core; the end face of the single-mode fiber is connected with the end face of the germanium wafer, and UV curing glue is coated between the connecting end faces of the single-mode fiber and the germanium wafer; the glass sleeve is fixedly sleeved on the outer side of the connecting position of the single-mode fiber and the germanium wafer. The optical fiber interference type sensor based on the germanium wafer and the manufacturing method thereof can dynamically monitor the change of the external temperature in real time, has high sensitivity and high resolution, is suitable for high-precision measurement of the temperature in a small area space, can replace an interference cavity rapidly and nondestructively, and meets the sensing application requirements of different resolutions and temperature ranges.

Description

A kind of optical fiber interference type sensor based on germanium wafer and its manufacturing method

Technical Field

The present invention relates to the technical field of temperature sensors, and in particular to a germanium wafer-based optical fiber interference sensor and a manufacturing method thereof.

Background technique

In the past decade, fiber optic sensing technology has made significant progress in engineering technology, aerospace, marine development and exploration, and fiber optic temperature sensors, as one of the key technologies, have always attracted much attention. The current mainstream temperature sensors mainly use electrical sensors, among which thermistors and platinum resistors are common temperature sensitive components. Although these traditional sensors are stable in low temperature environments, they have problems such as poor corrosion resistance, large size, difficult deployment, and electromagnetic interference. In contrast, fiber optic sensors have emerged in recent years, making up for the shortcomings of traditional electrical sensors and showing significant advantages. First, the sensing probe of the fiber optic sensor has the characteristics of low cost, light weight, small size, low loss, corrosion resistance, and electromagnetic interference resistance. These advantages make fiber optic sensors more flexible in application, especially in situations where the deployment space and weight requirements are high, fiber optic sensors have obvious advantages. Secondly, fiber optic sensors are easy to form an array, highly integrated, and can efficiently monitor temperature over a large range. This is particularly important for engineering projects that need to cover a wide area. Fiber optic sensors provide a more convenient and accurate means for monitoring and control through their integrated characteristics. In addition, fiber optic sensors have the characteristics of high sensitivity and easy long-distance signal transmission, which makes them play a unique role in application scenarios that require real-time monitoring and timely response.

Fiber FP interferometric sensors have the advantages of small size and suitability for special narrow spaces in terms of temperature sensing. However, fiber optic temperature sensors based on air interference cavities or fiber optic interference cavities are affected by the characteristics of the materials in the cavities, and have low sensitivity. Under the same free spectrum range, the resolution is even lower and cannot meet high-precision measurement requirements. In addition, the interference cavity length of the FP interferometric sensor will not affect the sensitivity of the sensor, but will change the temperature measurement range and temperature resolution of the sensor. Generally, after the FP interferometric fiber optic sensor is manufactured, the interference cavity cannot be replaced, and the only option is to cut off part of the optical fiber in the sensor head and remake it. When the signal light is introduced into the optical fiber, which is a more expensive multi-core optical fiber or sapphire optical fiber, the cost of the sensor will be greatly increased.

Summary of the invention

The purpose of the present invention is to provide a fiber optic interferometer sensor based on germanium wafer and a method for manufacturing the same. The sensor can dynamically monitor changes in external temperature in real time and has high sensitivity and high resolution. It is suitable for high-precision temperature measurement in a small area. The interference cavity can be replaced quickly and losslessly to meet the sensing application requirements of different resolutions and temperature ranges.

To achieve the above object, the present invention provides a germanium chip-based optical fiber interference sensor, comprising a single-mode optical fiber, a glass sleeve and a germanium chip; the single-mode optical fiber comprises an optical fiber core located inside and an optical fiber cladding wrapped outside the optical fiber core;

The end face of the single-mode optical fiber is connected to the end face of the germanium wafer, and UV curing glue is coated between the connection end faces of the single-mode optical fiber and the germanium wafer;

The glass sleeve is fixedly sleeved on the outer side of the connection position between the single-mode optical fiber and the germanium wafer.

Preferably, the inner diameter of the glass sleeve is the same as the outer diameter of the single-mode optical fiber, and the diameter of the germanium wafer is not greater than the inner diameter of the glass sleeve.

Preferably, the end face of the single-mode optical fiber is parallel to the end face of the germanium wafer, and the end face of the germanium wafer completely covers the end face of the optical fiber core.

Preferably, the cut surfaces of the optical fiber core and the optical fiber cladding at the end face of the single-mode optical fiber are smooth and flush, and the inner end face and the outer end face of the germanium wafer are polished and smooth.

Preferably, the length of the glass sleeve on a side close to the germanium wafer is not greater than the thickness of the germanium wafer.

A method for manufacturing a germanium wafer-based optical fiber interferometric sensor comprises the following steps:

S1, making double-sided polished germanium wafers;

S2. Remove the coating of the single-mode optical fiber using a wire stripper and cut it using a fiber cleaver to keep the end face of the single-mode optical fiber flat and smooth;

S3, take a section of glass sleeve and insert it into the end face of the single-mode optical fiber, wherein the length of the exposed portion of the outer glass sleeve is not greater than the thickness of the germanium wafer;

S4, using an optical fiber holder to vertically fix the single-mode optical fiber, with the end face of the single-mode optical fiber with the glass sleeve facing vertically downward;

S5. Place the germanium wafer directly below the single-mode optical fiber, and keep the end face of the single-mode optical fiber parallel to the upper surface of the germanium wafer;

S6. Apply a thin layer of UV curing glue on the upper surface of the germanium wafer, wherein the thickness of the UV curing glue does not exceed 10 microns;

S7. Slowly adjust the height of the fiber holder so that the germanium wafer is inserted into the glass sleeve and contacts the end face of the single-mode optical fiber;

S8. Fix the UV curing glue with an ultraviolet lamp, and the temperature sensor is completed.

Preferably, a method for losslessly replacing the sensor interference cavity is also included, and the specific method is as follows: connect the manufactured temperature sensor to a 980nm fiber laser, gradually increase the power of the 980nm fiber laser, so that the germanium wafer absorbs the laser and generates heat to above the melting point of the UV curing glue, the UV curing glue of the sensor head melts and evaporates due to the heat, use a clamping tool to separate the germanium wafer from the single-mode optical fiber, repeat the sensor manufacturing steps, and replace the germanium wafers with different cavity lengths.

Therefore, the beneficial effects of the present invention using the above-mentioned optical fiber interference sensor based on germanium wafer and its manufacturing method are as follows:

(1) The sensor probe has low production cost and simple production process.

(2) The sensor is light in weight and small in size, making it easier to integrate and make arrays.

(3) The thermo-optic coefficient of germanium wafer is high, about 4×10 ^-4 /K. The higher thermo-optic coefficient makes it have higher sensitivity. Compared with the intrinsic optical fiber temperature sensor, the sensor sensitivity can be increased by more than 150 times. Therefore, the sensor has higher resolution and is more suitable for high-precision temperature data monitoring.

(4) The sensor uses a germanium wafer as an interference cavity. Different interference cavity lengths have the same sensitivity, but different temperature measurement ranges and resolutions. This allows lossless interference cavity replacement of the sensor's light-guiding fiber, reducing the cost of sensor replacement.

The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a germanium wafer-based optical fiber interference sensor according to the present invention.

Reference numerals

1. Optical fiber core; 2. Optical fiber cladding; 3. Glass sleeve; 4. Germanium wafer; 5. UV curing adhesive.

Detailed ways

The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

The words "include" or "comprises" and the like used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements. The orientation or position relationship indicated by the terms "inside", "outside", "upper", "lower", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly specified and limited, the terms "attachment" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

Embodiment 1

As shown in FIG1 , the present invention provides a germanium chip-based optical fiber interference sensor, comprising a single-mode optical fiber, a glass sleeve 3 and a germanium chip 4 . The single-mode optical fiber comprises an internal optical fiber core 1 and an optical fiber cladding 2 wrapped around the optical fiber core 1 .

The end face of the single-mode optical fiber is connected to the end face of the germanium chip 4, and UV curing glue 5 is coated between the connecting end faces of the single-mode optical fiber and the germanium chip 4, wherein the coating thickness of the UV curing glue 5 needs to be controlled within 10 microns. In this embodiment, the coating thickness of the UV curing glue 5 is 5 microns.

The glass sleeve 3 is fixedly sleeved on the outer side of the connection position of the single-mode optical fiber and the germanium wafer 4, and is used to further fix the position of the single-mode optical fiber and the germanium wafer 4. The inner diameter of the glass sleeve 3 is the same as the outer diameter of the single-mode optical fiber, and the diameter of the germanium wafer 4 is not larger than the inner diameter of the glass sleeve 3. The length of the glass sleeve 3 on the side close to the germanium wafer 4 is not larger than the thickness of the germanium wafer 4.

The end face of the single-mode optical fiber is parallel to the end face of the germanium wafer 4, and the end face of the germanium wafer 4 completely covers the end face of the optical fiber core 1. The cut surfaces of the optical fiber core 1 and the optical fiber cladding 2 at the end face of the single-mode optical fiber are smooth and flush, and the inner and outer end faces of the germanium wafer 4 are polished and smooth to ensure that the sensor has high measurement accuracy.

The present invention provides a method for manufacturing a germanium wafer-based optical fiber interferometric sensor, comprising the following steps:

S1, making double-sided polished germanium wafers;

S2. Remove the coating layer of the single-mode optical fiber using a wire stripper and cut it using a fiber cleaver to keep the end face of the single-mode optical fiber flat and smooth;

S3, take a section of glass sleeve and insert it into the end face of the single-mode optical fiber, wherein the length of the exposed portion of the outer glass sleeve is not greater than the thickness of the germanium wafer;

S4, using an optical fiber holder to vertically fix the single-mode optical fiber, with the end face of the single-mode optical fiber with the glass sleeve facing vertically downward;

S5. Place the germanium wafer directly below the single-mode optical fiber, and keep the end face of the single-mode optical fiber parallel to the upper surface of the germanium wafer;

S6. Apply a thin layer of UV curing glue on the upper surface of the germanium wafer, wherein the thickness of the UV curing glue does not exceed 10 microns;

S7. Slowly adjust the height of the fiber holder so that the germanium wafer is inserted into the glass sleeve and contacts the end face of the single-mode optical fiber;

S8. Fix the UV curing glue with an ultraviolet lamp, and the temperature sensor is completed.

When it is necessary to select a different temperature measurement range, the sensor interference cavity can be replaced non-destructively. The specific method is as follows: connect the manufactured temperature sensor to the 980nm fiber laser, gradually increase the power of the 980nm fiber laser, so that the germanium wafer absorbs the laser and heats up to above the melting point of the UV curing glue. The UV curing glue of the sensor head melts and evaporates due to the heat. Use a clamping tool to separate the germanium wafer from the single-mode optical fiber, repeat the sensor manufacturing steps, and replace the germanium wafers with different cavity lengths.

Working principle of the present invention:

The sensor uses an infrared light source as a sensing light source, including but not limited to a broadband light source and a laser. The light source emits an optical signal that transmits the sensing light source to the sensor through a fiber coupler or fiber circulator. When the light enters the sensor, part of the light is reflected at the connection between the germanium wafer and the end face of the optical fiber, and part of the light enters the germanium wafer and is reflected at the second end face of the germanium wafer. During the reflection process, the two parts of light interfere with each other, and the interfering light signal passes through the fiber coupler or circulator again and enters the fiber spectrometer or photodetector for signal demodulation. The sensor is connected to the light source and the spectrometer (photodetector) through a fiber jumper. The light source provides a sensing light signal for the overall sensor, and the spectrometer (photodetector) can output the reflection spectrum of the sensor.

When the external temperature changes, the refractive index of the Fabry-Perot interferometer formed by the germanium wafer in the sensor probe will change, thereby affecting the optical path difference of the Fabry-Perot interferometer, and finally causing the position of the interference characteristic peak in the spectrometer to move. Therefore, by monitoring the position of the characteristic peak in the spectrometer, the change of the measured temperature can be obtained, thereby realizing temperature sensing.

When a fiber optic interferometer cavity with a different temperature measurement range is required, a 980nm laser can be incident through the light-guiding fiber, and the germanium wafer can be used to absorb the laser to achieve temperature increase. When the temperature reaches the melting point of the UV curing glue, the germanium wafer can be peeled off from the fiber end face, and the UV curing glue can be evaporated by high temperature. After that, the sensor production steps can be repeated, and the germanium wafers with different interferometer cavity lengths can be replaced to achieve sensor production with different temperature test ranges and resolutions.

Therefore, the present invention adopts the above-mentioned optical fiber interference sensor based on germanium wafer and its manufacturing method. The sensor can dynamically monitor the changes of external temperature in real time, and has high sensitivity and high resolution. It is suitable for high-precision temperature measurement in small areas. The interference cavity can be replaced quickly and losslessly to meet the sensing application requirements of different resolutions and temperature ranges.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims (2)

1. A method for manufacturing a germanium wafer-based optical fiber interferometric sensor, characterized in that: The sensor comprises a single-mode optical fiber, a glass sleeve and a germanium wafer; the single-mode optical fiber comprises an optical fiber core located inside and an optical fiber cladding wrapped outside the optical fiber core; The end face of the single-mode optical fiber is connected to the end face of the germanium wafer, and UV curing glue is coated between the connection end faces of the single-mode optical fiber and the germanium wafer; The glass sleeve is fixedly sleeved on the outer side of the connection position between the single-mode optical fiber and the germanium wafer; The inner diameter of the glass sleeve is the same as the outer diameter of the single-mode optical fiber, and the diameter of the germanium wafer is not greater than the inner diameter of the glass sleeve; The end face of the single-mode optical fiber is parallel to the end face of the germanium wafer, and the end face of the germanium wafer completely covers the end face of the optical fiber core; The cut surfaces of the optical fiber core and the optical fiber cladding at the end face of the single-mode optical fiber are smooth and flush, and the inner end face and the outer end face of the germanium wafer are polished and smooth; The length of the glass sleeve close to the germanium wafer is not greater than the thickness of the germanium wafer; The preparation method comprises the following steps: S1, making double-sided polished germanium wafers; S2. Remove the coating layer of the single-mode optical fiber using a wire stripper and cut it using a fiber cleaver to keep the end face of the single-mode optical fiber flat and smooth; S3, take a section of glass sleeve and insert it into the end face of the single-mode optical fiber, wherein the length of the exposed portion of the outer glass sleeve is not greater than the thickness of the germanium wafer; S4, using an optical fiber holder to vertically fix the single-mode optical fiber, with the end face of the single-mode optical fiber with the glass sleeve facing vertically downward; S5. Place the germanium wafer directly below the single-mode optical fiber, and keep the end face of the single-mode optical fiber parallel to the upper surface of the germanium wafer; S6. Apply a thin layer of UV curing glue on the upper surface of the germanium wafer, wherein the thickness of the UV curing glue does not exceed 10 microns; S7. Slowly adjust the height of the fiber holder so that the germanium wafer is inserted into the glass sleeve and contacts the end face of the single-mode optical fiber; S8. Fix the UV curing glue with an ultraviolet lamp, and the temperature sensor is completed. 2. The method for manufacturing a fiber optic interferometric sensor based on a germanium wafer according to claim 1 is characterized in that it also includes a method for non-destructively replacing the sensor interference cavity, and the specific method is as follows: connect the manufactured temperature sensor to a 980nm fiber laser, gradually increase the power of the 980nm fiber laser, so that the germanium wafer absorbs the laser and generates heat to a temperature above the melting point of the UV curing glue, the UV curing glue of the sensor head melts and evaporates due to the heat, use a clamping tool to separate the germanium wafer from the single-mode optical fiber, repeat the sensor manufacturing steps, and replace the germanium wafers with different cavity lengths.