Wavelength-switchable erbium-doped fiber ring laser employing chirped Moiré fiber grating and tunable Sagnac loop interferometer filter

Abstract

Abstract A simple, cost-effective and switchable five-wavelength fiber ring laser based on a chirped moire fiber grating (CMFG) and a wavelength-tunable Sagnac loop interferometer (FSI) f ilter is proposed and experimentally demonstrated. To serve as wavelength selective element, the CMFG possesses excellent comb-like filtering characteristics including stable wavelength interval and ultra-narrow passband, and its fabrication method is easy and flexible. The usage of the FSI filter helps remove the high-cost optical circulator and improve the output performance of optical signal-to-noise ratio from 50dB to 70dB. With this laser configuration, the output power fluctuation of each wavelength is less than 0.5 dB within a one-hour period, and the output power of different chan nels is almost identical (difference less than 1dB) within the tunable range. Key Words: fiber laser; chirped moire grating; Sagnac effect 1. INTRODUCTION Fiber lasers exhibit many attractive features such as inherent single transversal mode and compatibility with optical fiber systems. In recent years, there is a surge of interest in multi-wavelength and wavelength-switchable fiber lasers, since they are potentially useful for dense wavelength division multiplexed (DWDM) fiber communication systems, optical fiber sensor networks and instrumentation. The most important key component of these fiber lasers is a wavelength selection filter. Among versatile techniques to realize the wa velength selection filter, a fiber Bragg grating (FBG) is an ideal intra-cavity device to select the lasing wavelength, for example, the FBGs written in multimode fiber