CN113029426A

CN113029426A - Method for testing metal coating air pressure of femtosecond laser direct writing FBG

Info

Publication number: CN113029426A
Application number: CN202011431475.8A
Authority: CN
Inventors: 张雯; 祝连庆; 何巍; 董明利; 李红; 庄炜; 何彦霖
Original assignee: Beijing Information Science and Technology University
Current assignee: Beijing Information Science and Technology University
Priority date: 2020-12-07
Filing date: 2020-12-07
Publication date: 2021-06-25

Abstract

The invention relates to a femtosecond laser direct-writing Fiber Bragg Grating (FBG) metal coating air pressure probe. The sensor firstly uses a femtosecond laser direct writing technology to prepare the FBG, the optical fiber with the coating layer is arranged on a three-dimensional moving platform to ensure clear visual field, femtosecond laser facula is focused to a fiber core, and the FBG is prepared in a fiber core area by adopting a direct writing mode. And cutting off the fiber grating by using an optical fiber precision cutting device, and performing metal coating on the end face of the fiber grating to prepare the optical fiber air pressure probe. The metal coating air pressure probe of the femtosecond laser direct writing FBG manufactured by the technical scheme provided by the invention is of an all-fiber structure, can avoid electromagnetic interference, is high-temperature resistant, and has simple structure and manufacturing process, good reliability and high sensitivity.

Description

Method for testing metal coating air pressure of femtosecond laser direct writing FBG

Technical Field

The invention belongs to the field of optical fiber sensing devices, and particularly relates to a metal coating air pressure testing method of a femtosecond laser direct writing FBG.

Background

The optical fiber sensor has a plurality of excellent characteristics, can realize the measurement work under the complex environment and has very wide application value. The optical fiber has the characteristics of electromagnetic interference resistance, radiation resistance, high sensitivity, light weight, insulation, explosion resistance, corrosion resistance and the like, and the optical fiber has small size and good optical transmission performance. The Fiber Bragg Grating (FBG) is a common sensing device, has the advantages of simple structure, small volume, large dynamic range, high sensitivity and the like, and is widely concerned in important fields of aerospace, bridge water conservancy, perimeter security, biomedicine and the like. An FBG is a grating-like structure with a periodic distribution of spatial phases formed in the core, which essentially functions to form a narrow band filter or mirror in the core.

However, how to change the limitation of single-point detection of the conventional fiber FBG sensor and extend the range of the detection object is the development direction of the fiber sensor. The common optical fiber FBG sensor is of a cylindrical structure and cannot directly detect the pressure characteristics of the surrounding environment. Through carrying out metal coating at fiber grating's section, when the pressure size of external environment changed, the reflectivity of metal coating changed, leads to fiber grating reflection end's light intensity to change to realize the sensing of external atmospheric pressure environment.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a metal coating air pressure testing method of a femtosecond laser direct writing FBG.

In order to solve the technical problems, the invention adopts the technical scheme that: a preparation method of a metal coating air pressure probe of a femtosecond laser direct writing FBG (fiber Bragg Grating) specifically comprises the following steps:

(a) preparing a fiber Bragg grating by femtosecond laser, and placing a single-mode fiber with a coating layer on a three-dimensional mobile platform to ensure clear visual field in step a 1; a2, focusing femtosecond laser spots on a fiber core of the single-mode fiber, and preparing a fiber Bragg grating in the fiber core area by adopting a direct writing mode;

(b) preparing an optical fiber air pressure probe, and b1, positioning the optical fiber air pressure probe to the position of the fiber Bragg grating prepared by the femtosecond laser by adopting optical fiber precision cutting equipment, and cutting the optical fiber Bragg grating from the grating region to the cut position to form an end face; and b2, performing pressure sensitive metal coating on the end face to manufacture the optical fiber air pressure probe.

A femtosecond laser direct writing FBG metal coating air pressure test method specifically comprises the following steps: step 201, placing an optical fiber air pressure probe in a sealed air chamber, and connecting the optical fiber air pressure probe with a light source and an optical fiber sensing analyzer through an optical fiber circulator; step 202, changing the gas pressure in the environment to be tested of the optical fiber pressure probe, and carrying out a pressure sensing test; and 203, transmitting the reflection interference spectrum of the fiber Bragg grating to the optical fiber sensing analyzer by the optical fiber circulator, wherein the optical fiber sensing analyzer forms a reflection spectrum line.

Preferably, the light source adopts ASE light source with the wave band range of 1520 and 1610 nm.

Compared with the prior art, the invention has the beneficial effects that: the metal coating air pressure probe of the femtosecond laser direct writing FBG manufactured by the technical scheme provided by the invention is of an all-fiber structure, can avoid electromagnetic interference, is high-temperature resistant, and has the advantages of simple structure and manufacturing process, good reliability and high sensitivity.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Drawings

Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a process for preparing FBG based on femtosecond laser;

FIG. 2 is a structure of FBG fabricated in a core region by a direct writing method;

fig. 3 shows the reflection spectrum of FBG prepared in the core region by direct writing.

Fig. 4 shows the structural change of the FBG fabricated in the core region by the direct writing method when the air pressure of the external environment changes.

FIG. 5 is a diagram of the femtosecond laser direct-write FBG metal plating air pressure test system.

Fig. 6 is a reflection spectrum generated by the metal plating air pressure testing system of the femtosecond laser direct writing FBG of the present invention when the air pressure of the external environment is changed.

Detailed Description

The objects and functions of the present invention and methods for accomplishing the same will be apparent by reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The nature of the description is merely to assist those skilled in the relevant art in a comprehensive understanding of the specific details of the invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps.

The invention provides a femtosecond laser direct writing FBG metal coating air pressure probe, which is characterized in that the FBG structure is directly written on an optical fiber structure with a coating layer through femtosecond laser, a precise cutting device is used for cutting off an optical fiber grating, and metal coating is carried out on the end surface of the optical fiber grating, so that the optical fiber air pressure probe is manufactured.

In order to achieve the above-listed purposes, the technical scheme adopted by the invention is as follows:

a processing schematic diagram of FBG prepared based on femtosecond laser is shown in fig. 1, and the specific steps are as follows: the optical fiber with the coating layer is placed on a three-dimensional moving platform, the visual field is clear, femtosecond laser spots are focused to a fiber core, the FBG is prepared in the fiber core area in a direct writing mode, the structure is shown in figure 2, and the reflection spectrum is shown in figure 3.

And positioning the fiber grating position prepared by the femtosecond laser by adopting fiber precision cutting equipment, cutting off the grating region from the cut position, and performing pressure sensitive metal coating on the end surface of the grating region to prepare the fiber air pressure probe. When the air pressure of the external environment changes, the reflectivity of the metal coating changes, which results in the change of the bragg wavelength of the femtosecond laser direct-writing FBG (as shown in fig. 4). By demodulating the change of the wavelength, the sensing of the external environment air pressure can be realized.

The air pressure testing system for the metal coating of the femtosecond laser direct writing FBG is shown in figure 5. The optical fiber air pressure probe is arranged in the sealed air chamber and is connected with the light source and the optical fiber sensing analyzer through the optical fiber circulator. The light source adopts an ASE light source with the wave band range of 1520 and 1610nm, and the spectral analysis device adopts a spectral analyzer produced by Yokogawa company to collect the reflection spectrum in the experiment; the optical fiber circulator transmits the reflection interference spectrum of the optical fiber FBG to the optical fiber sensing analyzer. The optical fiber air pressure probe is arranged in the closed air chamber, and is used for controlling the air pressure in the environment to be tested to carry out air pressure sensing test.

The reflectance spectrum in the experiment is shown in FIG. 6. When the air pressure of the external environment changes, the reflectivity of the metal coating changes along with the change, so that the Bragg wavelength of the femtosecond laser direct writing FBG changes. By demodulating the change of the wavelength, the sensing of the external environment air pressure can be realized.

The invention has the beneficial effects that: the metal coating air pressure probe of the femtosecond laser direct writing FBG manufactured by the technical scheme provided by the invention is of an all-fiber structure, can avoid electromagnetic interference, is high-temperature resistant, and has the advantages of simple structure and manufacturing process, good reliability and high sensitivity.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A preparation method of a metal coating air pressure probe of a femtosecond laser direct writing FBG is characterized by comprising the following steps:

(a) preparing the fiber Bragg grating by femtosecond laser,

a1, placing the single-mode optical fiber with the coating layer on a three-dimensional moving platform to ensure clear visual field;

a2, focusing femtosecond laser spots on a fiber core of the single-mode fiber, and preparing a fiber Bragg grating in the fiber core area by adopting a direct writing mode;

(b) preparing an optical fiber air pressure probe, and preparing a probe,

b1, positioning the fiber Bragg grating prepared by the femtosecond laser by adopting fiber precision cutting equipment, and cutting the fiber Bragg grating from the cut part of the grating region to form an end face;

and b2, performing pressure sensitive metal coating on the end face to manufacture the optical fiber air pressure probe.

2. A femtosecond laser direct writing FBG metal coating air pressure test method is characterized by comprising the following steps:

step 201, placing an optical fiber air pressure probe in a sealed air chamber, and connecting the optical fiber air pressure probe with a light source and an optical fiber sensing analyzer through an optical fiber circulator;

step 202, changing the gas pressure in the environment to be tested of the optical fiber pressure probe, and carrying out a pressure sensing test;

and 203, transmitting the reflection interference spectrum of the fiber Bragg grating to the optical fiber sensing analyzer by the optical fiber circulator, wherein the optical fiber sensing analyzer forms a reflection spectrum line.

3. The method as claimed in claim 2, wherein the light source is ASE light source with a wavelength range of 1520 and 1610 nm.