Abstract

Soliton effects have been proposed as a means of attaining high contrast, complete pulse effects in waveguide (probably fiber based) devices.¹ We present the central concept which is that the integrity of solitons provides a nonlinear phase coherence (i.e., a nonlinear phase shift which applies throughout the pulse) thus allowing processing on the entire pulse in phase sensitive configurations. The generality of this concept is demonstrated by means of a simple but accurate model where the soliton phase is shown to be simply related to intensity and proportional to intensity. Examples of nonlinear interferometers in the Sagnac and Mach-Zehnder configurations are presented. The all-fiber realization of the Sagnac interferometer, the nonlinear optical loop mirror (NOLM), will emerge as a potentially useful device. In addition it is clearly shown that nonlinear directional couplers (e.g., twin cored fibers) fit in with the general concept. The simple model is shown to apply and conditions for achieving soliton switching are calculated. An experimental realization based on the NOLM is presented and results showing over 90% energy switching for subpicosecond pulses are displayed. Limitations imposed by the self-Raman effects are shown and an optimized configuration is presented.

© 1989 Optical Society of America