| 摘要 |
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.
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