CN111982346B

CN111982346B - High-sensitivity optical fiber temperature sensor

Info

Publication number: CN111982346B
Application number: CN201910441801.4A
Authority: CN
Inventors: 文晓艳; 南建; 张东生
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2019-05-24
Filing date: 2019-05-24
Publication date: 2022-05-03
Anticipated expiration: 2039-05-24
Also published as: CN111982346A

Abstract

The invention discloses a high-sensitivity optical fiber temperature sensor which comprises a lead-in optical fiber, a capillary collimator and an optical sheet. The optical sheet is directly connected with the capillary collimator, the lead-in optical fiber is connected with the capillary collimator, wherein two end faces of the optical sheet form an F-P cavity, and the lead-in optical fiber and the optical sheet form the F-P cavity. The lead-in optical fiber is used for leading in light source signals and transmitting reflected light. When the temperature changes, the capillary collimator and the optical sheet are subjected to thermal expansion, so that the two F-P cavities change to cause the spectrum to change, and ultrahigh temperature sensitivity is obtained. In addition, the optical sheet and the capillary collimator have low cost and simple manufacture, and the manufacturing cost of the sensor can be reduced without complex manufacturing process and expensive equipment.

Description

High-sensitivity optical fiber temperature sensor

Technical Field

The invention belongs to the technical field of optical fiber sensor manufacturing, and particularly relates to a high-sensitivity optical fiber temperature sensor.

Background

The advantages of the optical fiber sensor such as high sensitivity, electromagnetic interference resistance, good reliability, and abundant raw materials have attracted people's attention. Common fiber sensors include fiber gratings, fiber Sagnac interferometers, fiber mach-zehnder interferometers (MZIs), and fiber Fabry-Perot resonators. Among them, the vernier effect generated by the fiber Fabry-Perot resonator can be used to amplify the sensitivity of the sensor, so it has received much attention. For example, in 2009, Dai and Jin, etc. respectively propose vernier effect optical sensors based on a series optical fiber structure, and utilize a wavelength demodulation method to realize ultra-high sensitivity measurement of refractive index. In 2014, Zhang et al proposed a vernier effect fiber sensor which is used for measuring stress and magnetic field and has a cascaded FPI structure, wherein two sections of HC-PCF are embedded in a Single Mode Fiber (SMF) by utilizing the large mode field characteristic of a hollow photonic crystal fiber (HC-PCF), and the sensitivity of the vernier effect fiber sensor is improved by about 29 times compared with that of a single FPI, Shao et al proposed a vernier effect fiber temperature sensor of a tandem Sagnac interferometer, and the sensitivity of the vernier effect fiber temperature sensor is improved by about 9 times compared with that of a single Sagnac interferometer, but the size of the whole sensor is large (the length of a single Sagnac interferometer ring is about 2m), and the temperature measurement with high spatial resolution is difficult to realize. However, the above-mentioned sensors require expensive materials and equipment, and the production process is complicated, which is not favorable for mass production of the sensors.

Disclosure of Invention

The invention aims to solve the technical problem of providing a high-sensitivity optical fiber temperature sensor, which has obviously improved sensitivity to temperature, can be used in the field of precision measurement, and has the characteristics of low cost, simple structure and simple and easy preparation method.

The technical scheme adopted by the invention for solving the technical problems is as follows: a high-sensitivity optical fiber temperature sensor is provided, which comprises an optical fiber, a capillary collimator and an optical sheet, wherein one end of the capillary collimator is fixed with the optical sheet, and the optical fiber is inserted into the other end of the capillary collimator, two end faces of the optical sheet form an F-P cavity, and the optical fiber and the optical sheet form the F-P cavity. When the light beam is transmitted into the sensor, three reflected light beams are generated at the end face of the optical fiber and at the two end faces of the optical sheet. The three reflected lights form two F-P interferences, namely, one F-P interference is formed by the two reflected lights of the optical fiber and the contact surface of the optical sheet and the capillary collimator, one F-P interference is formed by the two reflected lights of the optical sheet, and one end surface of the optical sheet is used by the two F-P interferences at the same time. The Vernier effect is produced when the free spectral ranges of the two F-P interferences are close in size. The optical fiber is used for guiding light source signals and transmitting reflected light. When the temperature changes, the capillary collimator and the optical sheet are subjected to thermal expansion, so that the two F-P cavities change to cause the spectrum to change, and ultrahigh temperature sensitivity is obtained.

According to the technical scheme, the optical fiber is collimated by the capillary collimator, and the optical fiber is attached to the capillary collimator.

The difference between the inner diameter of the capillary collimator and the outer diameter of the optical fiber is less than 5%, and the collimation effect is achieved. At least one end of the capillary collimator is flat and the end is used for adhering an optical sheet.

According to the technical scheme, the optical sheet is fixed at one end of the capillary collimator tube in an adhesive bonding or resistance welding or pressure welding or laser welding mode.

According to the technical scheme, the optical sheets are polished on two sides and are parallel to each other.

According to the technical scheme, the optical sheet is a transparent sheet.

According to the technical scheme, the optical sheet is made of quartz or sapphire wafers or glass and is made of an optical material with the refractive index which is 0.2 different from that of the optical fiber.

The invention also provides a preparation method of the high-sensitivity optical fiber temperature sensor, which comprises the following steps of firstly, ultrasonically cleaning the capillary collimator and the optical sheet by using alcohol, then closely attaching the flat end surface of the capillary collimator to the optical sheet, and connecting the capillary collimator and the optical sheet; inserting the optical fiber into the capillary collimator, observing the spectrum in real time, and fixing the optical fiber and the capillary collimator when a preset spectrum appears; and step three, placing the manufactured optical fiber temperature sensor into a high-temperature furnace, and testing the temperature sensitivity and the response curve of the optical fiber temperature sensor to the temperature.

The invention has the following beneficial effects:

(1) when the temperature changes, the capillary collimator and the optical sheet are subjected to thermal expansion, so that the spectrum is subjected to obvious shift, and higher sensitivity can be obtained.

(2) The optical sheet and the capillary collimator are low in price, and the cost of the sensor is extremely low.

(3) The processing technology of the optical sheet is mature, the lengths of the two F-P can be well controlled, and the batch production is facilitated.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic structural diagram of an optical fiber temperature sensor according to an embodiment of the present invention;

FIG. 2 is a spectral diagram of a fiber optic sensor;

FIG. 3 is a graph of the spectrum of a fiber optic sensor at 310 ℃;

FIG. 4 is a spectrum of the fiber optic sensor at 315 deg.C;

FIG. 5 is a graph of the spectrum of a fiber optic sensor at 320 deg.C;

FIG. 6 is a graph of the spectrum of a fiber optic sensor at 325 deg.C;

FIG. 7 is a spectrum of the fiber optic sensor at 330 deg.C;

fig. 8 is a graph of the same valley position drift measurements as the sensor changes temperature.

Wherein, 1-capillary collimator; 2-an optical sheet; 3-a junction point; 4-optical fiber.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The first embodiment is as follows:

referring to fig. 1, in an embodiment of the present invention, a high-sensitivity optical fiber temperature sensor is provided, which includes an optical fiber, a capillary collimator, and an optical sheet, wherein the optical sheet is fixed at one end of the capillary collimator, and the optical fiber is inserted into the other end of the capillary collimator, wherein an F-P cavity is formed at two end faces of the optical sheet, and the optical fiber and the optical sheet form the F-P cavity. When the light beam is transmitted into the sensor, three reflected light beams are generated at the end face of the optical fiber and at the two end faces of the optical sheet. The three reflected lights form two F-P interferences, namely, one F-P interference is formed by the two reflected lights of the optical fiber and the contact surface of the optical sheet and the capillary collimator, one F-P interference is formed by the two reflected lights of the optical sheet, and one end surface of the optical sheet is used by the two F-P interferences at the same time. The Vernier effect is produced when the free spectral ranges of the two F-P interferences are close in size. The optical fiber is used for guiding light source signals and transmitting reflected light. When the temperature changes, the capillary collimator and the optical sheet are subjected to thermal expansion, so that the two F-P cavities change to cause the spectrum to change, and ultrahigh temperature sensitivity is obtained. The optical fiber is collimated by the capillary collimator and attached to the capillary collimator. The difference between the inner diameter of the capillary collimator and the outer diameter of the optical fiber is less than 5%, and the collimation effect is achieved. At least one end of the capillary collimator is flat and the end is used for adhering an optical sheet. And fixing an optical sheet at one end of the capillary collimator by using an adhesive sticking or resistance welding or pressure welding or laser welding mode. The optical sheets are double-side polished and parallel to each other. The optical sheet is made of quartz or sapphire wafer or glass and is an optical material with the refractive index different from that of the optical fiber by 0.2.

Example two:

selecting a ceramic ferrule as a capillary collimator, putting the ceramic ferrule into a beaker, adding alcohol into the beaker, and cleaning the ceramic ferrule for 3mins by using ultrasonic waves. The alcohol was then decanted, fresh alcohol was added, and the wash repeated 3 times. And after the ceramic ferrule is cleaned, heating the ceramic ferrule by using a heating plate to evaporate alcohol remained in the ceramic ferrule.

Then, the glass sheet having a thickness of 180um was taken out, and the glass sheet was washed by the same method. And horizontally placing the cleaned glass sheet on a clean platform, and then horizontally placing one end of the ceramic inserting core on the glass sheet for later use.

And uniformly stirring the two-component high-temperature adhesive DB5014 in a ratio of 1: 1. And dripping the prepared high-temperature adhesive at the joint of the ceramic ferrule and the glass sheet. And then, curing according to a curing method of the high-temperature adhesive.

And then the optical fiber connected with the jumper wire is inserted into the ceramic ferrule, and the jumper wire is connected into the demodulator to observe the spectrum change of the sensor in real time. And when the spectrum is changed into the spectrum in the figure 2, dropping high-temperature adhesive at the joint of the ceramic ferrule and the optical fiber, and curing. At this point the sensor fabrication is complete.

Fig. 1 shows a schematic structure diagram of a highly sensitive optical fiber temperature sensor. Fig. 2 shows a spectral diagram of a fiber sensor.

The spectra of the optical fiber sensor at 310 ℃ -325 ℃ are shown in fig. 3-7, and fig. 8 is a graph for measuring the drift of the same valley position of the sensor under the condition of temperature change according to the embodiment of the invention.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.

Claims

1. A method for preparing high-sensitivity optical fiber temperature sensor is characterized in that the optical fiber temperature sensor comprises an optical fiber, a capillary collimator and an optical sheet, wherein the optical sheet is fixed at one end of the capillary collimator, and the optical fiber is inserted into the other end of the capillary collimator, wherein an F-P cavity is formed on two end faces of the optical sheet, and the optical fiber and the optical sheet form the F-P cavity; aligning the optical fiber by a capillary collimator, attaching the optical fiber to the capillary collimator, and fixing an optical sheet at one end of the capillary collimator by using an adhesive bonding or resistance welding or pressure welding or laser welding mode; the preparation method comprises the following steps that firstly, the capillary collimator and the optical sheet are ultrasonically cleaned by alcohol, then the smooth end surface of the capillary collimator is tightly attached to the optical sheet, and the capillary collimator and the optical sheet are connected with the optical sheet; inserting the optical fiber into the capillary collimator, observing the spectrum in real time, and fixing the optical fiber and the capillary collimator when a preset spectrum appears; and step three, placing the manufactured optical fiber temperature sensor into a high-temperature furnace, and testing the temperature sensitivity and the response curve of the optical fiber temperature sensor to the temperature.