Pulse propagation in inhomogeneous optical waveguides. Final report, September 15, 1992--March 14, 1996

Abstract

Accomplishments include two Ph.D. dissertations, twenty-six archival journal publications that have appeared in print, six articles that have appeared in conference or summer school proceedings, sixteen regular conference presentations, and eleven invited conference presentations. A complete record of the publications and presentations may be found in Sec. II.E. The areas in which the author has been working--randomly varying optical fiber birefringence, passively modelocked lasers, and quasi-phase matched second harmonic generation--are all still of great current interest. Recent progress in soliton transmission has been nothing short of outstanding with the recent achievement of single channel 15 Gbit/sec, nearly error-free transmission over 35,000 km. At the same time, remarkable progress with the presently used NRZ (non-return-to-zero) transmission mode makes it less clear that solitons will ultimately be used. The author has contributed in important respects to all these areas. In long-distance transmission systems, the length scale on which the birefringence varies randomly (30--100 m) is short compared to the nonlinear and dispersive scale lengths (100--1,000 km). Consequently, it is crucial to understand and characterize this randomly varying birefringence when studying long-distance evolution in optical fibers. That has been done in a series of studies that has also led to the proposal of a numerical scheme for modeling these systems that should be orders of magnitude faster than the schemes presently being used. In the studies of the fiber ring and figure-8 lasers, the author proposed that nonlinear polarization rotation is the mechanism responsible for fast saturable absorption in the fiber ring lasers--a result that was later verified experimentally. He also explored a new approach to determining the conditions for modelocking and self-starting in these lasers that uses the computer to determine the linear stability of both the pulsed and cw solutions. In all this work, the author has worked closely with leading experimentalists and their groups. Section 2 of this report describes in more detail some of the specific accomplishments.