Chirp spectral pattern cavity-less optical fiber Fabry-Perot filter and manufacturing method thereof

Abstract

The invention discloses a chirp spectral pattern cavity-less optical fiber Fabry-Perot filter. The filter is characterized in that the filter comprises a multi-mode micro-nano optical fiber cladding,a multi-mode micro-nano optical fiber core and a Bragg grating; the multi-mode micro-nano optical fiber cladding is an outermost layer. According to the along-axis cross section of the multi-mode micro-nano optical fiber cladding, transition is realized from a uniform region with a constant radius to a micro-nano region with a gradually-changed radius, and again transition is realized from the micro-nano region with the gradually-changed radius to the other uniform region with a constant radius. The multi-mode micro-nano optical fiber core is an inner layer and is covered by the multi-mode micro-nano optical fiber cladding. According to the along-axis cross section of the multi-mode micro-nano optical fiber core, transition is realized from a uniform region with a constant radius to a micro-nano region with a gradually-changed radius, and again transition is realized from the micro-nano region with the gradually-changed radius to the other uniform region with a constant radius. The Bragg grating is a continuously-inscribed and equal-period Bragg grating which covers all the micro-nano region of the multi-mode micro-nano optical fiber core. With the chirp spectral pattern cavity-less optical fiber Fabry-Perot filter provided by the invention adopted, a chirp spectral pattern which can change in a free spectral range can be realized within a relatively large wavelength range, anda relatively large chirp rate can be realized. The chirp spectral pattern cavity-less optical fiber Fabry-Perot filter has the advantages of compact structure and easiness in manufacture.

Description

technical field [0001] The invention relates to the research field of optical devices, in particular to a chirp spectrum type cavityless optical fiber Fabry-Perot filter and a manufacturing method thereof. Background technique [0002] The chirped spectral multi-wavelength filter is a multi-wavelength device with non-uniform wavelength intervals, which is often used in the field of chirped signal generation. For example, in pulse compression technology, the use of frequency-time mapping technology and chirped spectral The spectral shaping technology of the optical filter can obtain the frequency-swept microwave pulse signal. [0003] In order to realize the chirped spectrum fiber shaping filter device, a feasible solution is to cascade fiber Bragg gratings with different bandwidths and interferometric fiber devices with specially designed phases. For fiber Bragg gratings cascaded with different bandwidths, it is very difficult to write because the grating period and modulat...

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Problems solved by technology

[0005] However, due to the existence of the cavity area, there will be two problems

First, since the effective refractive index does not vary greatly with the diameter in the two cone regions, the chirp rate of the interference spectrum is not very high

In addition, because the chirped gratings written in the two sections of the cone cannot guarantee complete symmetry, the wavelength ranges cannot be completely matched. Therefore, for the chirped interference spectrum, there will be a certain phase mismatch in the short-wave region, which will cause Destroy the chirp characteristics of the interference spectrum, so that there is a non-interference region, or a region where the chirp characteristics are reversed, which will affect its application effect

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