Tunable multimode-interference bandpass fiber filter
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Updated: Jun 16, 2026

Writing Bragg Gratings in Multicore Fibers
Published on: April 20, 2016
J E Antonio-Lopez1, A Castillo-Guzman, D A May-Arrioja
1Photonics and Optical Physics Laboratory, Optics Department, Instituto Nacional de Astrofísica,Optica y Electrónica, Tonantzintla, Puebla 72000, Mexico.
Abstract:
We report on a wavelength-tunable filter based on multimode interference (MMI) effects. A typical MMI filter consists of a multimode fiber (MMF) spliced between two single-mode fibers (SMF). The peak wavelength response of the filter exhibits a linear dependence when the length of the MMF is modified. Therefore a capillary tube filled with refractive-index-matching liquid is used to effectively increase the length of the MMF, and thus wavelength tuning is achieved. Using this filter a ring-based tunable erbium-doped fiber laser is demonstrated with a tunability of 30 nm, covering the full C-band.
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