Optics and Photonics 1 Dispersion Managed Solitons and Polarization Mode Dispersion

Communication systems utilizing dispersion managed solitons, still may not be deployed in spite of their excellent potential performance, because “linear propagation” using wavelength multiplexing has made enormous progress. However, bit-rates in individual channels are pushed upward, 40 Gb/s being under development. At high bit-rates, polarization mode dispersion (PMD) affects linear propagation adversely, putting a limit on the maximum transmissible bit-rate. PMD is caused by the unavoidable group velocity birefringence (two orthogonal polarizations travel at different group velocities). The principal polarizations vary randomly along the fiber. We have studied the effect of first order PMD on solitons and dispersion managed solitons and found that they display superior characteristics with regard to PMD. PMD excites internal oscillations of the soliton. The relative positions and the relative carrier frequency displacements of the two orthogonal polarizations behave like the position and momentum of a noise drive harmonic oscillator. The oscillations build up to a maximum level when the rate of excitation equals the rate of loss due to radiation (via the continuum). The soliton breaks up when the relative displacement approaches the width of the soliton. This puts an upper limit on the permissible PMD. This upper limit is independent of the bit-rate, unlike the case of linear propagation.