Gain flattening of an erbium-doped fiber amplifier using a high-birefringence fiber loop mirror

We propose a flexible method for flattening the gain profile of an erbium-d oped fiber amplifier (EDFA). The method is based on a high-birefringence fi ber loop mirror (HiBi-FLM), which contains a number of high-birefringence f iber sections and polarization controllers. We show that, by setting the po larization controllers properly, the reflection spectrum of the loop mirror can be adjusted to compensate for the variations in the gain profile of th e EDFA. The method is demonstrated experimentally by using a single-section HiBi-FLM and a two-section HiBi-FLM, respectively. With a two-section HiBi -FLM, we are able to flatten the gain profile of an EDFA to within +/- 0.9 dB over a bandwidth of 33 mn at the center wavelength of 1543 mn, under dif ferent operating conditions of the EDFA.