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Proceedings Paper

Steep and flat bandpass filter using linearly chirped and apodized fiber Bragg grating
Author(s): Xunqi Wu; Joël Jacquet; Guanghua Duan
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Paper Abstract

The development of new optical systems requires the design of novel components that fulfill the market constraints. In particular, low loss, high optical rejection and low cost narrowband filters can play an important role for the introduction of the Wavelength Division Multiplexing (WDM) technology in the local network. So, a novel fiber filter is proposed in this article, with a special combined apodized Linearly Chirped Fiber Bragg Grating (LCFBG) which presents the preferable flat-top and steep-edge characteristics. In the design, we use a continuum cavity condition which is obtained when the effective round-trip phase of oscillated wavelength band is kept identical over the whole Bragg wavelength range. And the transmission spectra are calculated by the reconstruction of the matrixes with the continuum oscillation condition. Therefore, our works show that the ideal square shaped filter is obtained with a lower chirp value relatively together with symmetric reflectivity on both mirrors. The coupling coefficient of the FBG is adjusted to get the same reflectivity values and then to get a transmission filter close to unity. We have then introduced an apodization function of the filter to get a flatter transfer function. Various apodizations schemes have been tested. In this paper, we design and analyze a type of continuum fiber filter with the cavity formed between mirror and apodized LCFBG as reflectors. We calculate firstly the reflectivity, the transmissivity and the group time delay of LCFBG modeled by a simple and practical Transfer Matrix Method (TMM), and then the cavity is reconstructed by TMM, the length of the oscillated cavity is calculated by the continuum oscillation condition, so the output of transmission from the side of LCFBG is continuous in the corresponded reflected bandwidth of LCFBG. We obtain the results and discuss some characteristics of this type of continuum fiber filter.

Paper Details

Date Published: 25 February 2010
PDF: 11 pages
Proc. SPIE 7598, Optical Components and Materials VII, 75981Y (25 February 2010); doi: 10.1117/12.842689
Show Author Affiliations
Xunqi Wu, Supélec, Lab. Matériaux Optiques Photonique et Systèmes, CNRS (France)
Joël Jacquet, Supélec, Lab. Matériaux Optiques Photonique et Systèmes, CNRS (France)
Guanghua Duan, Alcatel-Thalès III-V Lab. (France)

Published in SPIE Proceedings Vol. 7598:
Optical Components and Materials VII
Shibin Jiang; Michel J. F. Digonnet; John W. Glesener; J. Christopher Dries, Editor(s)

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