Wavelength control of erbium-doped fiber ring lasers by means of π-shifted variable long-period fiber gratings

Abstract

In this paper, fiber ring resonators are composed of an erbium-doped fiber amplifier (EDFA) with a π-shifted long-period fiber grating (PS-LPFG) to control the lasing wavelength. The PS-LPFG forms the passband inside the rejection band in the transmission spectrum, and the passband is shifted to longer wavelengths by stretching a coil spring that presses the fiber with an electromagnet. The oscillation wavelength is shifted from 1532.8 to 1565.1 nm depending on the variable grating period by using the C-band EDFA. By replacing to the L-band EDFA, the tunable wavelength range is moved to the range from 1586.8 to 1613.8 nm. The laser emission spectra exhibit the 3 dB spectral bandwidth of ~0.1 nm with a side-mode suppression ratio of ~40 dB.