Abstract: In the world of high speed communications where the use of return-to-zero modulation format is advantageous, there is a need for being able to exert electrical control, in a relatively simple manner, over the duty cycle of the optical pulses being generated without the undesirable effects of chirp, whilst providing good extinction between pulses. The invention proposes an optical pulse generator and methods of generating and shaping optical pulses using an arrangement of cascaded Mach-Zehnder type interferometers. The pulse generator has a signal generator that produces sinusoidal electrical modulation signals for application to the electrical inputs of cascaded Mach-Zehnder type interferometers. The first Mach-Zehnder type interferometer in the series is responsive to the sinusoidal electrical modulation signal being applied, to generate a series of optical pulses having controllable chirp.

Abstract: The optical modulator comprising an optical input signal waveguide, first and second interferometric waveguide arms, a modulated output signal waveguide, a splitter for dividing the input signal between the first and second arms, and a combiner for recombining the signals, transmitted along each of the first and second arms into the output signal waveguide. The first and second electrodes each of a segmented structure having a plurality of elements each extending from a respective one of the first and second electrodes and each terminating at position adjacent a length of corresponding one of the first and second arms wherein only a proportion of the elements terminate at positions such as to have an electro-optic effect on a signal transmitted through the corresponding one of the arms. Thus, only proportion of the elements are in active in the sense that only they induce a phase shift in the signal transmitted through the respective one of the arms.