Abstract

Over the past several years, many methods have been explored for the generation of high-repetition-rate trains of the nearly-transform-limited, sech-like pulses required for soliton transmission. To date, however, almost all methods that have been proposed for such pulse-train generation tend to have one or more drawbacks, such as excessive timing jitter, extreme chirp, difficulty of alignment, poor mechanical stability, high cost, and sensitivity to modulator bias drift. By contrast, a recently invented method,¹ involving nothing more than selection of the upper- or lower-frequency sidebands of a sinusoidally-phase-modulated cw source, suffers none of those drawbacks. In particular, it has been demonstrated, both theoretically and experimentally, that this simple and inexpensive method allows one to obtain nearly-transform-limited (chirp- free) pulses, at a repetition rate determined by the phase modulation frequency. Furthermore, because only the (time) derivative of the phase modulation matters, the generated pulse trains are completely unaffected by the bias drift inherent in most practical modulators, and so the pulse trains exhibit a high degree of long-term stability. The only potential drawback of this technique is the need to use optical filters with sharp response and to track the wavelength tuning of the cw laser and of the filters.

© 1995 Optical Society of America