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AssigneeFrance Telecom
InventorsDidier Herve, René Coquille, Jean-François Cadiou
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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.
A monitor device for monitoring a modulation frequency of an optical signal, the device being characterized in that it comprises a photorefractive crystal (7), a photodetector (6), and means (8a, 8b, 8c;
A device according to any preceding claim, characterized in that it has three fiber collimators (8a, 8b, 8c) which are fixed in position relative to said crystal (7) and which are connected respectively one to an optical fiber whereby a portion of the modulated optical signal is applied to the crystal (7), another to an optical fiber whereby the write optical signal is applied to the crystal (7), and the third to an optical fiber whereby the filtered signal as reflected by the crystal (7) is delivered to the photodetector (6).
A device according to any preceding claim, characterized in that the crystal (7) is a crystal of InP:Fe.
A device for monitoring the modulation frequency of an optical signal modulated at a microwave or millimetric frequency, characterized in that it is constituted by a device according to any preceding claim.
A device for monitoring the frequency of an oscillator whose output signal is used for modulating an optical signal, the device being characterized in that it comprises a servo-control loop which comprises:
Dependencies are inferred from the claim text.