L-I characteristics of fiber Bragg grating stabilized 980-nm pump lasers

Light versus current (L-I) characteristics, of fiber Bragg grating stabilized 980-nm pump lasers, is experimentally studied and theoretically modeled. It is shown that a conventional design of such laser modules can result in sudden transitions between a coherence-collapse multimode emission, and a coherent single-mode state of operation.

I. Introduction

THE INCREASING number of wavelength channels in dense wavelength-division-multiplexing (DWDM) applications requires tight control of the erbium-doped fiber amplifier (EDFA) gain flatness. This, in turn, is related to the pump laser specifications and, in particular, to its wavelength stabilization and control over an extended operating range and over a large variety of pump lasers. To this end, the locking of 980-nm pumps to external cavity fiber Bragg gratings (FBGs) has been considered and successfully employed [1]. Thus, FBG stabilization reduces thermal wavelength drift, eliminates chip-to-chip wavelength variations, and enables to combine several pump sources, within one single EDFA, to provide more pump power.