Composite structure long-period fiber grating

Abstract

The invention discloses a composite structure long-period fiber grating which comprises a fiber core, a fiber cladding and a fiber coating, wherein the fiber cladding coats the outside of the fiber core, the fiber coating coats the outside of the fiber cladding, and the fiber core belongs to the long-period fiber grating formed by a vertically staggered composite structure. The composite structure long-period fiber grating has a fine environmental response characteristic and a fine polarization characteristic, refractivity is vertically distributed in a staggered manner, and a fiber grating structure is enriched.

Description

technical field [0001] The invention relates to an optical fiber grating, in particular to a compound structure long-period optical fiber grating. Background technique [0002] Fiber Bragg Grating has the advantages of simple manufacturing process, low insertion loss, full compatibility with optical fibers, small size, and can be embedded in smart materials. It has been widely used in the fields of optical fiber communication and optical fiber sensing. Long-period fiber grating refers to a fiber grating with a grating period greater than 1 micron. Its coupling feature is the energy exchange between the fundamental mode transmitted in the core and the cladding modes of different orders transmitted in the cladding, resulting in a The related transmission loss is a very good band-stop filter device, and has the advantages of small additional loss, small back reflection, small size, etc., and can be widely used in optical fiber communication and sensing. [0003] Since the adve...

AI Technical Summary

Problems solved by technology

In recent years, with the development of the Internet of Things, long-period fiber gratings and core sensor devices have been vigorously developed. The basic sensing principle of long-period fiber gratings as optical fiber sensors is: when external environmental parameters such as temperature, strain, pressure, When the refractive index of the environment changes, the parameters of the resonant wavelength of the grating (generally referred to as the harmonic peak) such as wavelength position, amplitude, and polarization state change, so as to detect the change of the external environmental parameter by measuring the change of the harmonic wavelength parameter size, which realizes the measurement of environmental parameters. On the other hand, the period of the long-period fiber grating is relatively long, and the phase-matching condition is satisfied by the core fundamental mode and cladding mode propagating in the same direction, which will lead to long-period fiber The parameters of the resonant wavelength of the grating are very sensitive to changes in the external environment, so it has good sensitivity to temperature, strain, bending, twist, lateral load, concentration and refractive index. With the development of integration and miniaturization of optical fiber devices, There is an urgent need for long-period fiber gratings with multiple functions and multi-performance. Although there are different methods for writing long-period fiber gratings, the grating distribution (that is, the distribution of refractive index along the cross-section of the fiber core) has a single structure, which affects the long-period fiber grating. Development of Periodic Fiber Bragg Gratings

[0004] At present, there are mainly two forms of long-period fiber grating structures in the world according to the distribution of the refractive index of the cross-section of the grating. One is a uniform long-period fiber grating, that is, the refractive index changes uniformly along the cross-section of the optical fiber. The environmental response characteristics, that is, the sensing characteristics, but because the refractive index is uniformly distributed along the cross-section of the fiber and has no polarization-related characteristics, it is not suitable for some special purposes, such as long-wavelength fiber lasers, etc.; the other is tilted long-period fiber gratings, Since the refractive index distribution of the grating is non-uniform along the cross-section of the optical fiber, it has good polarization-dependent characteristics; however, due to the uneven distribution of the refractive index of the tilted grating and the need to accurately control the tilt angle, the difficulty of making the grating increases. Not easy to mass produce

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