Electrically tunable dual-wavelength switching in a mutually injection-locked erbium-doped fiber ring laser and distributed-feedback laser diode

Wavelength switching in a mutually injection-locked erbium-doped fiber ring laser and distributed-feedback laser diode (DFBLD) is experimentally demonstrated. By adjusting the power and the polarization state of injected light, three stable oscillation regimes were observed: Fabry-Pe/spl acute/rot (FP) mode oscillation, main distributed-feedback (DFB) mode oscillation, and dual-wavelength oscillation. Wavelength switching of 0.8 nm from one of the FP oscillation modes to the main DFB mode of the DFBLD is accomplished when the bias current to the DFBLD is varied from 9 to 14 mA. We also show that these wavelengths can be tuned as much as 2.48 nm when the temperature of the DFBLD is changed by 20/spl deg/C.

I. Introduction

There has been a lot of effort to realize optical switching in applications of wavelength-division-multiplexed optical networks [1], [2]. Fig. 1. Configuration of a mutually injection-locked laser system with an EDFRL and a DFBLD. For fast wavelength switching, distributed Bragg reflector lasers [3] and an external cavity Fabry–Pérot laser diode (FPLD) with a cascaded fiber Bragg grating [4] were developed. Wavelength switching in an erbium-doped fiber laser by using loss modulation of one of lasing modes was demonstrated with an optical chopper [5], cascaded fiber gratings [6], and fiber Sagnac loop reflectors [7]. Compared to multiwavelength switching, dual-wavelength switching is desired for some applications such as differential absorption spectroscopy (DAS) [8]. In this letter, we report a tunable dual-wavelength switching laser realized by a mutually injection-locked laser system composed of an erbium-doped fiber ring laser (EDFRL) and a distributed-feedback laser diode (DFBLD). Mutually injection-locked laser system with an EDFRL and a DFBLD was first demonstrated by Liou et al. [9]. Another mutually injection-locked system with an EDFRL and an FPLD was investigated in detail [10] later. Compared to those previous results, we obtained a delicate operation condition for the three stable oscillation regimes by controlling polarization states and the feedback power level too. Wavelength switching between two wavelengths is demonstrated by changing the bias current to the DFBLD by only 5 mA. The linewidth and the wavelength tuning range of the laser system before and after switching is also investigated.