Polarization-independent transmission on a single mode fiber using coherence modulation of light

A polarization-independent transmission link on a single mode fiber at 1300-nm wavelength is demonstrated using coherence multiplexing. The use of a source with a very short coherence length (about 200 μm) allows an easy implementation of the suitable optical delays (some millimeters) using LiNbO₃ modulators matched to fiber interferometers. Experiments were conducted with transmission of analog signals and baseband TV signals on a 2500-m-long single mode fiber. The polarization-independence of the method is obtained at the cost of relatively high losses. The high losses are introduced by the interferometers that are required at both ends of the link (theoretical losses of -3 dB/interferometer). They are physically inherent in the coding and detection process, which requires optical delays greater than the coherence length, and hence cannot be decreased