Input polarization-independent multi-channel switching using cascaded long-period fiber grating and polarization-maintaining fiber

Chang-Seok Kim,Young-Geun Han,Jin U Kang,John S Nelson,Bernard Choi

doi:10.1117/12.589710

Abstract

Novel multi-wavelength switching filters based on cascaded long-period fiber grating (LPG) and polarization-maintaining fiber (PMF) in a Sagnac loop configuration are proposed and experimentally demonstrated. While the multi-channel spectrum of PMF Sagnac loop filter is controlled by the polarization state in the loop, the polarization-independence of the LPG filter is used to drop one channel. The polarization-independence of the cascaded LPG filter is also used for the fixed periodic loss spectrum to drop multiple channels in the loop. Although the polarization state of the optical wave filter is switched by the electro-optic modulator in the loop, the device is independent of the polarization state of the input light due to the bi-directional polarization compensation of the Sagnac loop interferometer. This device can be used to achieve all-channel gating and odd/even-channel switching with fine channel selectivity and high speed response.

Highlights

Multi-channel switching devices have received considerable attention in recent years for their applications in wavelength-division-multiplexed (WDM) communications, wavelength-domain biomedical imaging systems, and sensor applications [1,2,3]
In the polarization maintaining fiber (PMF) Sagnac loop (PSL) filter, the spacing of multi-wavelength channels can be simultaneously controlled by the multiple PMF sections and relative polarization state in the loop the Sagnac loop is independent of the polarization state of input light [4]
Unique advantages of both cascaded long-period fiber grating (LPG) and PMF Sagnac loop are combined in novel configurations for polarizationindependent multi-wavelength channel switching filter

Summary

INTRODUCTION

Multi-channel switching devices have received considerable attention in recent years for their applications in wavelength-division-multiplexed (WDM) communications, wavelength-domain biomedical imaging systems, and sensor applications [1,2,3]. Fiber-based interferometer, such as polarization maintaining fiber (PMF) Sagnac loop filter [4] and long-period fiber gratings (LPGs) filter [5], have been independently developed for multi-wavelength filtering applications. In the PMF Sagnac loop (PSL) filter, the spacing of multi-wavelength channels can be simultaneously controlled by the multiple PMF sections and relative polarization state in the loop the Sagnac loop is independent of the polarization state of input light [4]. Multi-wavelength channel can be achieved with cascaded LPGs pair. Unique advantages of both cascaded LPGs and PMF Sagnac loop are combined in novel configurations for polarizationindependent multi-wavelength channel switching filter. The proposed device has a lot of advantages like the rapid response time and fine channel selectivity

PMF SAGNAC LOOP FILTER

COMBINED FILTER

CONCLUSION