Multiwavelength Erbium-Doped Fiber Laser Employing Cavity Loss Modulation

A novel and simple multiwavelength erbium-doped fiber laser is proposed and demonstrated. The combination of a polarization scrambler and a polarizer is employed to induce polarization-dependent-loss modulation. The loss modulation induced multiwavelength lasing by alleviating the mode competition caused by homogeneous gain broadening of the erbium-doped fiber. As a result, 11-wavelength lasing operation with wavelength spacing of 0.8 nm has been achieved. The output power distribution is quite uniform and the power fluctuation of each wavelength is smaller than 0.6 dB.

I. Introduction

Multiwavelength erbium-doped fiber lasers (EDFLs) attract much interest due to their potential applications in fiber sensing, component testing, optical signal processing, and wavelength-division-multiplexing optical communication systems. Different techniques have been proposed to realize multiwavelength oscillations at room temperature in EDFLs. These include the introduction of polarization hole burning effect by using polarization-dependent elements in the laser cavities [1]–[3], and nonlinear optical approaches by inducing various nonlinear effects such as four-wave mixing [4] and stimulated Brillouin scattering [5] in the laser cavity. Room-temperature multiwavelength operation in an EDFL has been also reported in [6] by inserting a frequency shifter in the laser cavity to prevent steady-state oscillations. Other methods of incorporating in the laser cavity a length of multimode fiber [7] or a multimode fiber Bragg grating [8], employing specially designed erbium-doped fibers (EDFs) [9] or cavity structures [2], [10] were also reported. Recently, multiwavelength single frequency operation was also obtained by dual-pumping a distributed Fabry–Pérot (F-P) feedback structure[11].