Polarization effects in wavelength-stabilized pump laser modules

Fiber Bragg grating (FBG) stabilized 980 nm LD pump laser modules are key components for erbium-doped fiber amplifier systems (EDFAs). For EDFA designers it is important to understand the effects of varying effective feedback on the pump laser properties. We present a new model, based on an extension of the well-known traveling-wave amplifier model that allows us to calculate polarization-dependent contributions to the power from fiber, back-facet power, and fiber coupling losses. Both TE- and TM-polarized fractions of the light fed back into the laser cavity are fully taken into account. The model is experimentally verified using the set-up and method As an important result, we find that for a given FBG reflectivity both the threshold current and the back-facet power strongly depend on the effective feedback level, whereas the power from fiber is much less affected.