INCREASING REPEATER SPAN IN HIGH-SPEED BIDIRECTIONAL WDM TRANSMISSION-SYSTEMS USING A NEW BIDIRECTIONAL EDFA CONFIGURATION

When fiber-optic systems contain erbium-doped fiber amplifiers (EDFA), reflections are enhanced by the gain of the amplifiers and severe sys tem performance degradations and bit-error-rate (BER) doors can be obs erved, This provides a very restrictive limit on the usable amplifier gain, We present a new configuration for a bidirectional EDFA that all ows for a significantly higher maximum allowable gain while introducin g a very small BER penalty, A 2.5 Gb/s, 300 Km bidirectional wavelengt h-division multiplexing (WDM) transmission experiment using the new bi directional EDFA is reported, Experimental results show that allowable gain of the new EDFA is significantly increased while the associated EER penalty remains negligible.