Polarization effects on ultralong distance signal transmission in amplified optical-fiber loops

Abstract
The authors report on the transmission mode of an optically amplified loop caused by polarization-dependent loss and optical filtering within the loop. A 2-Gb/s optical pulse stream was propagated over 400000 km in the low-pass polarization eigenstate of a 100-km amplified optical-fiber loop. The low-error-rate transmission distance was limited to 9000 km by signal-spontaneous beat noise. Other transmission modes of amplified loops are described.