Abstract: This invention relates generally to custom optical filters such as filters relating to, flat-top WDM multiplexer/demultiplexers, flat-top and peaky comb filters or reconfigurable add & drop filters. The embodiment disclosed below is based on mid-dispersion wavelength bands processing, wherein the optical spectrum is dispersed in two steps; in-between these two steps, the wavelength bands are manipulated in the focal plane, for example by being moved, reflected, absorbed, inverted, magnified or reduced to achieve a particular result. A masked mirror or masked transmissive element selects wavelength by position. The mask shape for relatively complex filtering functions is much simpler than currently used for collimated beams because of the correlation between position and wavelength. Inversion of channel bands or movement of channel bands in two dimensions in the focal plane, in particular, enables the construction of numerous useful devices.

Abstract: An optical preamplifier device for a light receiver, the device including a first optical amplifier. The first optical amplifier is coupled to an input of an optical filter centered around a fixed wavelength .lambda..sub.o via a wavelength conversion device for converting wavelength to the fixed wavelength .lambda..sub.o of the filter, thereby enabling the device to be made independent of the wavelength .lambda..sub.i of the signal.

Abstract: A semiconductor optical amplifier includes in integrated form a linear response attenuation segment in series between first and second amplification segments. The amplifier can be used to implement a high-speed wavelength converter that can be used with advantage in an optical telecommunication system.

Abstract: A semiconductor substrate includes an active waveguide to guide optical signals to be amplified occupying signal channels within a gain band of the waveguide. A stabilizer system comprises two Bragg reflectors tuned to a resonant wavelength in the gain band but outside the signal channels. It includes a gain segment in a resonant cavity. Two rejector Bragg reflectors sandwiching the resonant cavity between them are tuned to the resonant wavelength. Applications include telecommunication systems.