France Telecom

France Telecom Etablissement Autonome De Droit Public

Fabrice Devaux

Francis Pirio

Abderrahim Ramdane

Abdallah Ougazzaden

An inline modulator device for an optical transmission system, the device comprising: detector means suitable for detecting a portion of the signal transmitted on the line; modulator means; and a control circuit adjustable for synchronization, serving to extract the clock from the signal coming from the detector means and, on the basis of said clock, generating a modulation control signal which it applies to the modulator means, wherein the detector means and the modulator means are constituted respectively by the inlet section and the outlet section of an electro-absorbent modulator constituted by a two-section integrated component, such that said detector means and modulator means can be placed in the line in the form of a single insertion. The present invention also provides optical telecommunications systems using such an inline modulator device.

Inline modulator device for an optical transmission system

An integrated monolithic laser-modulator component having a multiple quantum well structure. This component includes an InP substrate, a laser (L) formed from a stack of semiconductor layers epitaxied on the substrate, including an active and absorbent layer and a periodic Bragg grating fixing the emission wavelength of the laser to a value slightly above an optimum wavelength of the laser gain peak. An electrooptical modulator (M) is formed from the same stack of semiconductor layers, with the exception of the Bragg grating, the active layer of the laser and the absorbing layer of the modulator being formed by the same epitaxied structure having several constrained or unconstrained quantum wells, the modulator functioning according to a confined Stark effect. The semiconductor layers of the laser and those of the modulator are electrically controlled.

Integrated monolithic laser-modulator component with multiple quantum

Apparatus for reshaping a train of light pulses includes an electro-absorbent modulator to which the train of pulses is applied for the purpose of being resynchronized and reshaped. A periodic signal generator that is adjustable in phase and frequency applies a periodic signal to the modulator to voltage control said modulator. Servo-control means control said generator in phase and in frequency to minimize the mean photocurrent delivered by the modulator while it is both in its absorbent state and receiving a light pulse. The apparatus may also be used to recover a periodic signal that is synchronized on a train of modulated light pulses. The invention is applicable to long distance telecommunications by transmitting soliton pulses along optical fibers.

Apparatus for re-shaping a train of light pulses, and apparatus for

The light pulse generator includes a source for generating a light beam, an electroabsorbent modulator for modulating the light beam into light pulses, and means for applying voltage control to the modulator. The electroabsorbent modulator includes at least two doped layers and between them at least one intermediate layer that is made of a material that is not intentionally doped, and that has an electroabsorbent material included therein. The absorbent or transparent state of the intermediate layer is controlled by a voltage applied between two of the doped layers that have doping of the same sign, the transmissivity of the modulator as a function of the voltage controlling it being at a maximum in the vicinity of zero volts and being symmetrical thereabout.

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Paris, France

Fabrice Devaux