Abstract: Apparatus of the invention includes:a diffraction grating for angularly separating the spectrum components of a beam to be processed;a grating that is conjugate with the other grating, and that makes the components parallel again; anda stair-shaped mirror for reflecting the components back to the same gratings while imposing different path lengths on the respective components.The invention is particularly applicable to compensating for the dispersion of a line fiber in a very long link between a transmitter and a receiver.

Abstract: An amplifying optical fiber amplifies a plurality of wavelength-multiplexed carrier waves. The invention enables the gain as seen by each of the carrier waves to be maintained, in particular when the total input power varies. For that purpose, amplified spontaneous "reverse" emission light is servo-controlled in power. After being filtered in a filter and detected by a photodiode, said light controls the powering current supplied to two laser diodes for pumping the fiber. The invention applies in particular to implementing optical transmission networks.

Abstract: An electrical power supply (20, 22) powers a semiconductor laser chip (2) under gain switching conditions so as to make the chip emit light pulses. The light pulses are compressed in a fiber (30) having negative dispersion, so that they constitute solitons. Their spectrum width is decreased by the fact that a gain segment powered by the power supply constitutes only a portion of the length of the resonant cavity of the chip. The invention applies to transmitting data over optical fibers.

Abstract: Transmission line sections in a connection comprise passive portions transmitting the signal without compensating for its natural attenuation and occupying 15% to 65% of the length of the section. They also include active portions that amplify the signal. The invention is particularly applicable to making intercontinental connections.

Abstract: An optical communication link with correction of non-linear effects comprises an optical fiber transmission line subject to chromatic dispersion and non-linear effects and correction means for limiting the disadvantageous consequences of this dispersion and/or these non-linear effects. The correction means comprise at the output of the transmission line a dispersion compensator adapted to apply dispersion in the opposite direction to and of lower absolute value than the dispersion due to the transmission line.

Abstract: The source includes an electro-absorption modulator receiving a continuous light wave supplied by a laser emitter 10. The characteristic response curve of the modulator has a threshold so that the modulator transmits an optical pulse having a duration which is less than the duration of an electrical control pulse which is applied to the modulator by a control generator. Soliton-type optical pulses obtained in this way are transmitted via a line fiber to a receiver. Application to optical transmission.

Abstract: A photodiode (26) receives an optical input signal (P1) and an internal optical signal (P2) and supplies in response thereto an internal electrical signal (I2), which in turn controls a laser (4) which effects amplification and supplies the internal optical signal and an output signal (P3). The feedback loop formed by this photodiode and laser leads to a strong non-linearity in the variation of the output signal as a function of the input signal. The invention is useful especially in optical fiber telecommunications systems.

Abstract: A semiconductor laser (2) constitutes a monolithic source whose intensity is modulated at a frequency lying in the microwave frequency range, typically 10-20 GHz to 100 GHz. It is based on coupling between the longitudinal modes of the laser, with intensity modulation being given by beats between the various modes of the laser. Optimization and control of the laser are made possible by splitting the optical cavity (6, 8, 10) of the laser into successive sections (20, 22, 24). The invention is particularly suitable for telecommunications applications.

Abstract: A femtosecond dye laser comprises a dye amplifier assembly (30) pumped by a mode-locked neodymium YAG laser (35) operating with frequency doubling. The main dye laser cavity as defined on one side of the amplifier assembly (30) by a linear prism structure (11 and 14) leading to an outlet mirror (15), and on the other side of the amplifier assembly by an assembly (20) constituting an anti-resonant mirror disposed about a saturable absorption device (40). An error signal is tapped by leakage from one of the mirrors (22) and is spectrally analyzed and compared with a reference wavelength (at 50) enabling a high tension amplifier (60) to be controlled to act on a piezo-electric stack (19) in order to fix the position of the outlet mirror (15) so as to adjust the optical length of the cavity as a function of the spectral characteristics of the pulses it produces.