Power unbalanced polarization-division-multiplexing for efficient bandwidth utilization

Summary form only given. There has recently been a capacity explosion of optical fiber links due to techniques such as WDM. However, WDM high-capacity systems are straining to accommodate either smaller channel wavelength spacing or wider wavelength range in order to continue the growth in capacity. Channel spacings are limited by many factors, including: optical filters, wavelength drifts, signal bandwidth, EDFA bandwidth, and dispersion and nonlinearities. One method of readily increasing the utilization of the available bandwidth is polarization-division-multiplexing (PDM), in which independent signals are simultaneously transmitted on orthogonal polarizations. However, PDM has traditionally been thought to be fairly impractical because of randomly varying fiber birefringence that scrambles a signal's state-of-polarization (SOP) during propagation. Under such conditions, two data streams on two orthogonal polarizations cannot be demultiplexed at the receiver since the input SOP is not easily recoverable. We propose and experimentally implement a method of multiplexing two orthogonal polarizations of the same wavelength in a power ratio of 1:2 to facilitate the straightforward decoding of the two data channels. Our technique effectively replicates a 4-ray optical signal, and does not require the demultiplexing of the two orthogonal polarizations and the recovery of the input SOP at the receiver.