Multi-wavelength fiber ring laser with switchable fiber Bragg gratings

Abstract

Various techniques have been suggested to build a fiber ring laser using a fiber Bragg gratings (FBG) as a lasing wavelength selection filter. For most of FBG filter, a circulator has been used as a key component to convert the reflection characteristic of FBG to the transmission spectrum, but it has been hard to tune the spectral reflectance or transmittance of FBG intrinsically. In this research, a multi-wavelength fiber ring laser is proposed based on a novel switchable bandpass filter to show tunable multiple lasing spectra with high extinction. The proposed switchable bandpass filter consists of multiple FBG's incorporating Sagnac loop interferometer configuration. Transmission spectra of bandpass filter can be greatly varied for more than 20 dB as changing the phase of polarization controller in the Sagnac loop. We experimentally demonstrate the lasing wavelength is easily selected by the switchable FBG's at multiple spectral positions.