Narrowband, polarization insensitive all-fiber acousto-optic tunable bandpass filter

Kwang Jo Lee,Byoung Yoon Kim,Dong-Il Yeom

doi:10.1364/oe.15.002987

Abstract

We demonstrate an all-fiber acousto-optic tunable bandpass filter exhibiting narrow optical bandwidth and negligible polarization dependence by employing a novel ultraviolet (UV)-induced core-mode blocker written in a high numerical aperture (NA) fiber. It was demonstrated that the device had the measured 3-dB optical bandwidth of 0.65 nm, the polarization-dependent center-wavelength splitting of 0.05 nm and the extinction ratio of -22dB at the wavelength around 1550 nm. The details of the transmission characteristics and the loss mechanism of the core-mode blocking element inscribed in the high NA fiber are discussed.

Highlights

Tunable bandpass filters are key components in optical communication networks and optical sensor systems
We demonstrate an all-fiber acousto-optic tunable bandpass filter exhibiting narrow optical bandwidth and negligible polarization dependence by employing a novel ultraviolet (UV)-induced core-mode blocker written in a high numerical aperture (NA) fiber
Some key features required for a practical acousto-optic tunable bandpass filter (AOTBF) include availability of narrow linewidth, negligible polarization dependence, low loss, small form factor, high extinction ratio, environmental stability, and in some cases, no frequency shift

Summary

Introduction

Tunable bandpass filters are key components in optical communication networks and optical sensor systems. Some key features required for a practical acousto-optic tunable bandpass filter (AOTBF) include availability of narrow linewidth, negligible polarization dependence, low loss, small form factor, high extinction ratio, environmental stability, and in some cases, no frequency shift. We demonstrate an AOTBF that satisfies all of the desired properties mentioned above having narrow bandwidth (0.65 nm), low polarization dependent loss (0.18dB), low insertion loss (1dB), small form factor, and zero frequency shift. These properties were made possible by using a newly developed ultraviolet (UV)-induced coremode blocker and a dispersion compensating fiber (DCF) [7]. The narrow bandwidth results from highly dispersive core mode, and the polarization insensitivity comes from the reduced thermal stress effect caused by the small core and depressed cladding structure [8]

Experiment and analysis

Findings

Conclusion