| 摘要 |
A modulator arrangement for modulating an optical signal using a quadrature phase shift key for use in an optical wavelength division multiplex (WDM) optical communications system comprising a laser ( 2 ) for producing an optical signal of a selected wavelength, which signal is split by a splitter ( 4 ), each part of said split signal being applied to a respective phase modulator ( 6, 8 ) each for which phase modulators is adapted to modulate the phase of the signal in dependence on a respective drive voltages. The phase of the output of at least one modulator ( 6 ) is shiftable at least in part by a phase shifter ( 10 ), the split signals being recombined by an optical recombiner ( 12 ) to form an optical phase shift key output, wherein the output power is monitored by a detector ( 20 ), the detector signal then being used to drive a feedback arrangement to control electrodes of the phase modulators ( 6, 8 ) and/or phase shifter ( 10 ). |
