Highly efficient all-fiber tunable polarization filter using torsional acoustic wave

Kwang Jo Lee,Byoung Yoon Kim,Hyun Chul Park

doi:10.1364/oe.15.012362

Abstract

We demonstrate an all-fiber tunable polarization filter with high coupling efficiency based on acousto-optic coupling between two optical polarization modes of the LP(01) mode propagating in a highly birefringent single mode optical fiber. An over-coupling between the two polarization modes is realized over the wavelength range from 1530 nm to 1610 nm using traveling torsional acoustic wave. The measured 3-dB optical bandwidth of the filter was 4.8 nm at the wavelength around 1550 nm. The details of the filter transmission and the coupling characteristics are discussed.

Highlights

Tunable optical filters are key components in optical communication networks and optical sensor systems
It has been known that AO coupling between two optical polarization modes in a highly birefringent (HB) optical fiber can be realized using traveling torsional acoustic wave, which is one of the three acoustic modes propagating in a cylindrical optical fiber without cutoff when the acoustic wavelength is much longer than the dimension of the fiber core [4, 5]
We demonstrate, for the first time to our knowledge, that a full coupling can be achieved in an all-fiber acousto-optic tunable polarization filter (AOTPF) using the lowest torsional acoustic mode traveling in a HB single mode optical fiber

Summary

Introduction

Tunable optical filters are key components in optical communication networks and optical sensor systems. Practical AOTFs with a simple structure for various applications such as optical switches and wavelength tuning devices have been realized as notch type [2] or bandpass type [3]. (AO) devices are based on wavelength selective AO coupling between several spatial modes of light propagating in an optical fibers using traveling flexural acoustic wave. We demonstrate, for the first time to our knowledge, that a full coupling can be achieved in an all-fiber acousto-optic tunable polarization filter (AOTPF) using the lowest torsional acoustic mode traveling in a HB single mode optical fiber. The complete optical power transfer between two polarization modes is realized over the wavelength range from 1530 nm to 1610 nm by employing a newly designed transducer that efficiently generates torsional acoustic wave in the fiber. The coupling characteristics between two optical polarization modes by the lowest torsional acoustic mode and the transmission characteristics of the fabricated filter are discussed in detail

Principles of operation

Experiment and analysis

Findings

Conclusion