UNIMPAIRED TRANSMISSION THROUGH A BIDIRECTIONAL ERBIUM-DOPED FIBER AMPLIFIER NEAR LASING THRESHOLD

We present transmission experiments with an erbium doped fiber amplifi er (EDFA) without optical isolators, designed for bidirectional transm ission. The combination of high gain and reflections/Rayleigh backscat tering may result in laser action of the EDFA at the maximum-gain wave length 1531 nm. It was demonstrated that wavelength-selective transmis sion at 1537 nm was unimpaired for G(1531)(2) R(1)R(2) less than or eq ual to -15 dB. The gain saturation due to laser action and the multipl e-reflection penalty were both less than 0.5 dB. A specification for t he allowable maximum gain of a bidirectional EDFA is derived.