An Electronically Wavelength Tunable Mode-Locked Fiber Laser Using an All-Fiber Acousto-Optic Tunable Filter

Abstract

Ultra short pulse generation from a fiber laser is a challenging subject for applications in all-fiber optic telecommunications. The wavelength tuning capability of the short pulse fiber lasers has recently gathered much attention for its potential application in WDM systems. Mollenauer et al. have demonstrated a tunable soliton laser utilizing a Fabry-Perot filter and a frequency shifter [1]. This method is based on the continuous frequency shifting and spectral filtering of the light in the laser cavity with an advantage of Gordon-Hous jitter reduction. A sliding frequency soliton laser with an all-fiber configuration has been reported by incorporating with an acousto-optic filter/frequency shifter based on a null coupler [2]. The all-fiber filter/frequency shifter have much low insertion loss compared to the bulk-optic counterparts such as the Fabry-Perot filter and the Bragg-cell used in Ref. 1. However, with this all-fiber device, continuous wavelength tuning has been achieved over only few nanometers because of the nonuniform spectral transmission characteristics of the device showing sidelobes beside the central peak, and relatively long pulses of 18 ps width have been generated. In this paper, we demonstrate a wavelength tunable sliding frequency mode-locked laser operation of a nonlinear amplifying loop mirror — Faraday rotator mirror (NALM-FRM) laser by using an all-fiber acousto-optic tunable filter (AOTF)/frequency shifter based on two-mode fiber. Stable and high peak powered subpicosecond-long pulses are obtained over a wide tuning range.