A temperature-insensitive erbium-doped fiber amplifier for terrestrial wavelength-division-multiplexing systems

We have evaluated a variation in the temperature dependence of an erbium-doped fiber gain spectrum by a pump wavelength in the 980-nm band for the first time. By optimizing both the pump wavelength in the 980-nm band and a temperature-sensitive gain flattening filter, the gain change of an erbium-doped fiber amplifier was successfully suppressed to 0.18 dB/sub pp/ in the temperature range between 0/spl deg/C and 65/spl deg/C and the wavelength range of 37.0 nm.

I. Introduction

Increasing the transmission capacity and reach of wavelength-division-multiplexing (WDM) systems has prompted erbium-doped fiber amplifiers (EDFAs) to expand their gain bandwidth and maintain a flat gain spectrum. Fig. 1. Experimental setup for measurement of EDF gain spectra Furthermore, the EDFAs recently have been required to decrease electric power consumption for cost-effectiveness. In long-haul terrestrial WDM systems, the temperature of erbium-doped fiber (EDF) is controlled so as to be constant, because the gain profile of EDF is varied by temperature [1]–[3]. In order to reduce the electrical power consumption of the EDFAs, the gain variation by temperature must be suppressed without the electrical temperature control scheme. It has been proposed to employ a temperature-sensitive gain flattening filter (GFF) which compensates the temperature dependence of EDF gain [4], [5].