Abstract

Improving receiver sensitivity under direct detection has become possible with recent progress in Er-doped fiber amplifiers (EDFAs).¹ Although a backward pumped EDFA has lower insertion loss than a forward pumped EDFA, the previous experiments^2,3 have been carried out using forward pumped EDFAs. This is because of the difficulty in achieving low noise and high-gain characteristics simultaneously in backward pumping.⁴ However, if low noise operation could be obtained under backward pumping, substantially higher sensitivity could be achieved.

© 1992 Optical Society of America