Cascade long-period fiber grating device, manufacturing method thereof, and humidity sensing system

A fiber grating and long-period technology, which is applied in the field of sensor measurement, can solve the problem of low resolution of long-period fiber gratings, and achieve the effect of improving resolution

Inactive Publication Date: 2009-12-02
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0007] In order to overcome the problem of low resolution caused by a single long-period fiber grating due to the grating spectral width, the purpose of the present invention is to provide

Method used

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  • Cascade long-period fiber grating device, manufacturing method thereof, and humidity sensing system
  • Cascade long-period fiber grating device, manufacturing method thereof, and humidity sensing system
  • Cascade long-period fiber grating device, manufacturing method thereof, and humidity sensing system

Examples

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Embodiment 1

[0052] The cascaded long-period fiber grating device according to this embodiment includes a first long-period fiber grating, a second long-period fiber grating, and an optical fiber. The first long-period fiber grating is used to receive the optical signal and divide it into two paths, one path is transmitted through the fiber core, and the other path is coupled to the fiber cladding for transmission. The light intensities of the two paths separated by the first long-period fiber grating are equal, and it is preferable to make the two paths of light intensities equal during the manufacturing process, and it is also possible to be unequal, but the interference contrast will be relatively poor. The second long-period fiber grating is used to receive the transmitted two-way optical signals through the optical fiber, and couple the optical signals transmitted in the optical fiber cladding back to the optical fiber core. The distance between the center of the first long-period fib...

Embodiment 2

[0060] In this embodiment, the hydrogel humidity sensitive film is coated on the surface of the cascaded long-period fiber grating device in embodiment 1 to form a humidity sensor, which includes two asymmetric long-period fiber gratings separated by a certain distance, and Hydrogel humidity sensitive membrane.

[0061] One of the preferred implementations of the humidity sensor, such as image 3 As shown, the humidity sensor includes: two first long-period fiber gratings 301 and a second long-period fiber grating 302 whose transmittance is 3dB, the distance between the two gratings is L, and the fiber cladding between the two gratings The surface is coated with a hydrogel humidity sensitive film 303 to realize the perception of changes in the humidity of the external environment.

[0062] Such as Figure 4 It is a structural diagram of another embodiment of the cascaded long-period fiber grating humidity sensor. Its structure is basically the same as that of Example 1, exce...

Embodiment 3

[0065] Such as Figure 5 As shown, the humidity sensor includes two asymmetric long-period fiber gratings 501 and 502 separated by a certain distance L with a transmittance of 3 dB, and a hydrogel humidity sensitive film 503 . The hydrogel humidity-sensitive film 503 is produced by the method of soaking combined with ultraviolet lamp irradiation film formation. First, a layer of hydrogel is coated on the surface of the optical fiber cladding by the soaking method, and then the hydrogel-coated cascade length The two ends of the periodic fiber grating device are fixed with optical fiber clamps 504 to ensure that the entire optical fiber is in a straight state, and the entire optical fiber is placed under an ultraviolet lamp 505, and polymerization is initiated by ultraviolet light irradiation to obtain a hydrogel humidity sensitive film 503 .

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Abstract

The invention relates to a cascade long-period fiber grating device, a manufacturing method thereof, a humidity sensor and a humidity sensing system. The humidity sensing system comprises a broadband light source, a Mach-Zehnder interferometer, a humidity sensitive film, a spectrum collection unit and a data processing unit, wherein the Mach-Zehnder interferometer is formed by connecting two long-period fiber gratings alternately in certain distance; two ends of the interferometer are connected with the broadband light source and the spectrum collection unit; the humidity sensitive film is used for sensing information of environment humidity variations; the spectrum collection unit is used for collecting the information of the environment humidity variations; and the data processing unit is used for analyzing and processing collected optical interference signals containing environment humidity information, and acquiring environment humidity to be detected finally. The spectrum has finer structure and narrower line width, solves the problems of low sensitivity and resolution in the prior art, can perform remote real-time online monitoring, and has accurate measurement and low cost.

Description

technical field [0001] The invention relates to the field of sensor measurement, in particular to a cascaded long-period optical fiber grating device and a manufacturing method thereof, a humidity sensor and a humidity-sensitive sensing system using the cascaded long-period optical fiber grating device. Background technique [0002] Long-period fiber gratings are a type of grating with a period of tens to hundreds of microns. It forms a periodic geometric structure change or refractive index modulation along the fiber axis through ultraviolet irradiation, arc discharge, and laser thermal effects. This kind of fiber grating is characterized by coupling the forward propagating core mode to the forward propagating cladding mode, resulting in transmission loss at the corresponding wavelength, and one or more loss peaks appear in the transmission spectrum. Long-period fiber grating is a fiber sensor with excellent performance. Compared with the wide application of fiber Bragg gra...

Claims

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Application Information

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IPC IPC(8): G02B6/02G01N21/45
Inventor 于秀娟张敏陈明华廖延彪居剑靳伟
Owner TSINGHUA UNIV
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