Abstract:
A method and apparatus is provided for controlling the bias point of a Mach-Zehnder modulator. The method begins by applying a dither signal to a DC bias that is applied to a Mach-Zehnder modulator. A component of an optical output signal provided by the Mach-Zehnder modulator that is synchronous with the dither signal is detected. The dither signal is adjusted to maintain the detected component of the optical output signal at a substantially constant value.
Abstract:
A quantum-confined Stark effect quantum-dot optical modulator (115) includes an interferometer (130) having a beam splitter (135), first and second parallel optical branches (140a,140b) fed by the beam splitter (135) and a beam combiner (145) fed by the first and second parallel optical branches and a laser (110) for feeding a laser beam to the beam splitter. First and second optical phase shifters (150a,150b) are provided in respective ones of the first and second parallel optical branches. Each optical phase shifter includes an intrinsic semiconductor crystalline planar layer and p-type and n-type planar semiconductor layers on opposite faces of the intrinsic semiconductor crystalline planar layer, the intrinsic layer lying in a plane parallel to a direction of propagation of the laser beam in the respective optical branch. The intrinsic layer has plural layers of planar arrays of quantum dots therein. A reverse bias D.C. voltage source (320,325) is connected across the p-type and n-type layers.
Abstract:
A semiconductor Mach-Zehnder modulator comprises a pair of phase modulator arm waveguides (8A-1, 8A-2) for a push-pull modulation. A first electrode (13-1) connected to p-type cladding layer (4-1) of modulator arm (8A-1) is maintained at a negative potential V π , a second electrode (13-2) connected to n-type cladding layer (2-1a) of modulator arm (8A-1) and p-type cladding layer (4-2) of modulator arm (8A-2) is driven by a drive voltage, and a third electrode (13-3) connected to n-type cladding layer (2a-2) of modulator arm (8A-2) is maintained at a ground potential. The drive voltage changes between V π , and V π/2 for push-pull modulation by both modulator arms (8A-1, 8A-2).
Abstract:
Ce séparateur est par exemple réalisé sur LiNbO₃:Ti en coupe X, propagation Z et comprend, en série, un embranchement en Y passif (66), un déphaseur actif (68) et un coupleur directif actif (70), indépendant de la polarisation, apte à constituer un coupleur 3 dB. Ainsi, lorsqu'on envoie à l'entrée de l'embranchement en Y une onde lumineuse et que le coupleur constitue un coupleur 3dB, on obtient les modes TM et TE de l'onde d'entrée respectivement aux sorties du coupleur en polarisant convenablement le déphaseur. Application aux capteurs à fibres optiques et à la transmission cohérente d'informations par fibres optiques monomodes.