SWITCHABLE DELAYS OPTICAL FIBRE TRANSPONDER WITH OPTICAL GENERATION OF DOPPLER SHIFT

摘要

The invention concerns an optical modulator, comprising an input suitable to receive an optical carrier, a high- frequency microwave input and an output suitable to transmit an optical signal, the optical modulator comprising two Mach-Zender (1,2) modulators in parallel between the input and output so as to constitute two different optical paths within a third Mach-Zender modulator (3), the optical modulator being characterised in that: - the first Mach-Zender modulator (1) is provided with an electrode suitable to apply two microwave signals (RFl, RF2) obtained by the sum of the two tones fR and fD of equal power, the signals being dephased by pi/2, the modulator (1) being further provided with an electrode (Bias 1) for realising a single side band modulation of the tones fR and fp; - the second Mach-Zender modulator (2) is provided with an electrode (Bias 2) to vary the phase and the amplitude of the optical carrier; the third Mach-Zender modulator (3) comprises an electrode • (Bias 3) suitable to realise the summation of the signals deriving from the first (1) and the second (2) Mach-Zender modulator before the output, so as to suppress the optical carrier and thus obtain only the tones fR and fo in the optical spectrum. The invention further concerns an optical generator of Doppler frequency, an optical link for the generation of a variable optical delay and a transponder, in particular for the calibration, the test and the performances test of a radar, in particular a phased-array radar, that uses the optical modulator according to the invention.