Polarization-coupling all-fiber acousto-optic tunable filter insensitive to fiber bend and physical contact

Kwang Jo Lee,Hyun Chul Park,In-Kag Hwang,Byoung Yoon Kim

doi:10.1364/oe.17.006096

Abstract

We show that an all-fiber acousto-optic tunable filter based on polarization mode coupling using torsional acoustic wave is immune to the fiber bend and physical contact in the acousto-optic interaction region. We also propose and demonstrate a novel strain-free and size-reduced tunable filter with a 4-m-long fiber acousto-optic interaction region looped into a 5- cm-diameter coil.

Highlights

Tunable wavelength filters are key components for optical sensors and communication systems
We show that an all-fiber acousto-optic tunable filter based on polarization mode coupling using torsional acoustic wave is immune to the fiber bend and physical contact in the acousto-optic interaction region
We report our new findings in that the optical and acoustic properties of the torsional mode acousto-optic tunable filters (AOTFs) are surprisingly insensitive to fiber bending and physical contact in the AO interaction region

Summary

Introduction

Tunable wavelength filters are key components for optical sensors and communication systems. It should be noted that a small non-circularity of the fiber cross-section introduces acoustic birefringence for flexural wave that results in complexity in output filter spectrum [8] These advantageous features of torsional mode AOTFs are important for realizing robust and high-performance optical devices for practical applications. We report our new findings in that the optical and acoustic properties of the torsional mode AOTF are surprisingly insensitive to fiber bending and physical contact in the AO interaction region This is in great contrast to the case of the flexural mode AOTF, for which the bending and the physical contact of the fiber result in significant deterioration of the output filter spectrum and coupling efficiency [10,11,12,13]. We propose and demonstrate a novel strain-free and compact all-fiber torsional mode AOTF by coiling the fiber in the AO interaction region

Perturbation effects in all-fiber torsional mode AOTF

Conclusion