Flat-Topped Spectral Response in a Ladder-Type Interferometric Filter

Seok-Hwan JEONG
Shinji MATSUO
Yuzo YOSHIKUNI
Toru SEGAWA
Yoshitaka OHISO
Hiroyuki SUZUKI

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C    No.8    pp.1747-1754
Publication Date: 2005/08/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.8.1747
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Optoelectronics
Keyword: 
optical filters,  flattened filter response,  waveguide device,  multimode interference coupler,  

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Summary: 
We propose and demonstrate a novel ladder interferometric filter that exhibits flat-topped spectral response for use in wavelength-division-multiplexing (WDM) based photonic networks. We numerically analyze the flattened spectral response in a ladder-type filter by modifying the transfer matrix of ladder interferometer. Conventional parabolic-shaped and flat-topped-designed ladder interferometric filters are fabricated, and characterized. We demonstrate a flat-topped filter response in the fabricated device. The shape factor, which is defined by the ratio of -1 dB bandwidth to -10 dB bandwidth, is improved from 0.32 to 0.54. The tunability and the increase in filter extinction ratio of the proposed device are also discussed.