Abstract: The invention concerns a device for temporal subsampling of an OTDM optical signal at a predetermined subsampling frequency, comprising a generator (10) for generating clock pulses transmitted at the predetermined subsampling frequency and at a conversion wavelength ?H and a wavelength converter device (16) adapted to receive at its input the OTDM optical signal and the clock pulses in order to deliver at its output a subsampled OTDM optical signal at the conversion wavelength. The converter device comprises a linear optical amplifier (18) adapted to receive the OTDM optical signal and the clock pulses propagating in the opposite direction, the maximum linear power of the conversion being adjusted so that it can be less than the peak power of the OTDM optical signal, and a converter (20) of phase modulation into amplitude modulation.

Abstract: The invention concerns a device for temporal subsampling of an OTDM optical signal at a predetermined subsampling frequency, comprising a generator (10) for generating clock pulses transmitted at the predetermined subsampling frequency and at a conversion wavelength ?H and a wavelength converter device (16) adapted to receive at its input the OTDM optical signal and the clock pulses in order to deliver at its output a subsampled OTDM optical signal at the conversion wavelength. The converter device comprises a linear optical amplifier (18) adapted to receive the OTDM optical signal and the clock pulses propagating in the opposite direction, the maximum linear power of the conversion being adjusted so that it can be less than the peak power of the OTDM optical signal, and a converter (20) of phase modulation into amplitude modulation.

Abstract: A device for monitoring a modulation frequency of an optical signal,—in particular a device for monitoring the modulation frequency of an optical signal modulated at a microwave or millimetric frequency—, the device being characterized in that it comprises a photorefractive crystal (7), a photodetector (6), and means (8a, 8b, 8c; 9a, 9b, 9c) for applying to said crystal (7) firstly at least a fraction of the modulated optical signal and secondly a write optical signal for photoinducing a Bragg grating on said crystal (7), the orientations of the modulated optical signal and of the write optical signal relative to said crystal (7) being such that at a given wavelength of the optical signal the photodetector (6) detects an intensity for the signal reflected by the crystal (7) that reaches a maximum when the optical signal is modulated at the modulation frequency to be detected.

Abstract: The present invention relates to a process for the preparation of mono-crystalline 3-5 semi-insulating materails by doping, characterized in that the starting charge of type .rho. is doped with at least one deep donor due to a transition element. It relates also to the use of the semi-insulating materials obtained in the fields of optoelectronics and of rapid electronics.