Optical implementation of a space-time-trellis code for enhancing the tolerance of systems to polarization-dependent loss.

We propose a space-time coding scheme designed to increase the tolerance of fiber-optic communications systems to polarization-dependent loss (PDL). A notable increase in the tolerable amount of average link PDL is achieved without affecting the complexity of the overall optical communications link. Other advantages include seamless integration with the broadly deployed blind equalization modules relying on the constant modulus algorithm.

Beneficial use of spectral broadening resulting from the nonlinearity of the fiber-optic channel.

We discuss the possibility of exploiting spectral broadening resulting from fiber nonlinearity for the transmission of information. The spectral broadening induced by nonlinearity combined with the appropriate waveform can turn quadrature amplitude modulation-like constellations into frequency-shift-keying constellations over a much larger dimension. Thus, the Kerr effect can be thought of as a large dimensional mapper/modulator. A simple single-span fiber-optic link implemented over dispersion shifted fiber is assumed for the demonstration of the principle. It is shown that for a particular constellation the achievable data rates in the presence of nonlinearity can be significantly higher than the capacity characterizing a linear channel with the same input bandwidth.

Use of space-time coding in coherent polarization-multiplexed systems suffering from polarization-dependent loss.

We evaluate the advantage of using space-time coding in order to increase the tolerance of fiber-optic communications systems to polarization-dependent loss (PDL). Focusing on three particular codes, the Golden Code, the Silver Code (SC), and the Alamouti Code (AC), we calculate the amount of average PDL that can be tolerated for a given signal-to-noise ratio margin that is designed into the system. The SC is shown to be optimal in the case of low to moderate PDL, whereas, in the case of extreme PDL, the AC shows the best performance.

Capacity limitations in fiber-optic communication systems as a result of polarization-dependent loss.

We characterize the effect of polarization dependent loss (PDL) on the information capacity of fiber-optic channels. The reduction in the outage capacity owing to the PDL is quantified as well as the signal-to-noise ratio margin that needs to be allocated for the PDL in order to avoid loss of capacity.