Method for manufacturing phase-shift optical fiber grating by modulating optical fiber local temperature

Abstract

The invention is based on an existing fiber grating producing technique. The invention combines a device which is used for producing common even fiber Bragg gratings and an outer heat source. Temperature distribution on a fiber can be changed through an outer heating method, compared with left and right portions of the fiber, a large temperature rising is provided with an axial partial of the fiber, a Bragg grating is evenly written on the fiber, under normal temperature, the Bragg grating can be changed into a fiber grating whose partial is provided with an uneven period, the partial uneven period produces phase shifts effects on grating spectra properties, a heating device is arranged on a moving platform which is controlled through a computer and can be moved axially along the fiber, heating for different points in a fiber grating producing area can be realized, and thereby we can introduce the phase shifts to the different points of the fiber conveniently. The invention method can be realized conveniently, the invention has popular adaptability for various methods of producing the even fiber Bragg gratings, different phase shifts can be introduced through controlling suitably heating points and heating temperatures, and thereby different phase shift fiber gratings can be produced.

Description

1. Technical field [0001] A method for fabricating a phase-shifting fiber grating through local temperature modulation of an optical fiber belongs to the technical field of fiber grating manufacturing. 2. Technical background [0002] Phase-shifted fiber grating is a fiber grating with a sudden change in the axial refractive index change period. It opens one or more transmission windows with extremely narrow line width in the stop band of the Bragg reflection spectrum, so that the grating is sensitive to a certain wavelength or multiple wavelengths. With higher selectivity, it has received extensive attention in the fields of filtering, wavelength division multiplexing, and gain flattening of erbium-doped fibers, especially fiber DFB lasers based on π-phase-shifted fiber gratings, which have outstanding features of narrow linewidth and stable frequency. The advantage is that it is an ideal device for making single-frequency fiber lasers and has been developed rapidly. [00...

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Problems solved by technology

[0004] At present, there are basically four methods for producing phase-shifted fiber gratings: the first displacement method uses a precision translation stage to precisely control the exposure position and introduce phase shift by moving the optical fiber or fiber Bragg grating mask to produce high-quality phase-shifted optical fiber grating, but this method requires high precision of the movement of the stage, and it is necessary to use an expensive nano-scale precision moving platform to produce a high-quality phase-shifted fiber grating; Exposure introduces phase shift into the secondary exposure method. Since the production of a phase shift grating needs to adjust the optical path back and forth, the production efficiency is low, and the consistency of the produced phase shift grating is poor; the third method is to directly write the phase shift into the phase shift mask. This method is suitable for the production of large quantities of phase-shifting fiber gratings of uniform type, but only one phase-shifting grating corresponding to the phase mask can be produced, and the phase-shifting mask is expensive, and a mask can only Manufacturing a certain number of fiber gratings results in limited types of gratings and high production costs; the fourth is the equivalent phase shift method that introduces equivalent phase shifts, which introduces phase shifts by changing the sampling period of the sampled gratings, but this method produces Compared with the ideal situation, the spectral characteristics of the equivalent phase shift grating are quite different

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