In accordance with the invention, a modulated RZ pulse source comprises a modulated light source optically coupled to a stabilized Bragg grating filter and one or more optical taps. The light source is preferably modulated in power and frequency and has an adjustable channel wavelength . The Bragg grating filter has a reflectivity bandwidth having a high slope reflectivity cutoff and is preferably tunable. A feedback arrangement responsive to the taps keeps the source channel wavelength on the edge of the reflectivity bandwidth for shaping RZ pulses. When the Bragg grating is stabilized, the feedback system maintains at a value linked to the grating reflectivity edge and, by overlapping at least part of the optical spectrum of the source, converts the modulated source light into RZ pulses with high extinction ratio (12 dB). The result is a high power, jitter-free RZ pulse source that is compact, inexpensive and power efficient.