Interferometric noise in lightwave systems with optical preamplifiers

Penalties from multi-path interference in transmission systems employing optical preamplifiers have been investigated experimentally as well as theoretically. Calculations of the fraction of errors originating from the four possible combinations of received and interfering bit are carried out to identify the dominant cause of the power penalties. With perfect extinction ratio, the penalties from phase noise induced intensity noise (PIIN) are significant only at moderate levels of relative crosstalk (-30 dB to -18 dB), whereas the error floors (infinite penalty) are caused by beat noise originating from crosstalk and amplified spontaneous emission and a reduction in extinction ratio. Nonperfect extinction ratios increases the sensitivity to PIIN.