Abstract

In the last few years, the erbium-doped fiber amplifiers (EDFAs) have been investigated extensively for both their superior amplification characteristics and the compatibility to optical fiber communication systems. Long-distance transmissions with EDFAs have been successfully demonstrated[l]. If we apply an EDFA in front of the receiver as an optical preamplifier, we can improve the receiver sensitivity by increasing signal level above the receiver noise level. This preamplification technique is very effective, particularly for higher bit rate systems. This is because the receiver noise increases with increasing bit rates, and the presently-available APDs have difficulty in simultaneously satisfying sufficient multiplication and bandwidth. We have previously shown the effectiveness of the EDF preamplifier at 10 Gb/s under 1.48 μm pumping[2]. In order to get higher sensitivity, how ever, the 0.98 μm pumping will be preferable to the 1.48 μm pumping owing to lower noise property, and this has been tested at bit rates less than 2.5 Gb/s by using a Ti:Sapphire laser as a pump light source[3].

© 1991 Optical Society of America