Subpicosecond pulse propagation in fiber optic transmission systems

Abstract

The speed of advanced fiber optic transmission systems demonstrated in research laboratories has been limited by the speed of optoelectronic components, but not yet by fiber dispersion. As optoelectronic speeds approach and exceed 50 Gbit/s the optical bandwidth is so large that fiber dispersion will limit transmission distances even at the minimum dispersion wavelength k0. In this paper we map the ultimate theoretical limits due to the combined effects of dispersion, self-phase modulation, and fiber loss in an ideal transmission channel. We employ the techniques used in ultrashort pulse research but cast them in a unified approach more familiar to system designers. We also show that the limitations imposed by second- and third-order fiber dispersion may be eliminated by dispersion compensation with a grating pair. Second- and third-order dispersion compensation may be accomplished for wavelengths a few nanometers longer than k0. Numerical evaluation of precompensated pulse propagation in fibers using the modified nonlinear Schrodinger equation shows that subpicosecond pulses may be transmitted, distortion free, for many tens of kilometers in an ideal fiber. Grating compensation of fiber dispersion will be especially significant in ultrabroadband systems such as wavelength multiplexing and femtosecond multiple access schemes.