| 摘要 |
A modulator arrangement for modulating an optical signal using a differential quadrature phase shift key for use in an optical wavelength division multiplex (WDM) optical communications system comprising a laser 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 ). The phase modulators ( 6, 8 ) are adapted to modulate the phase of the signal in dependence on a respective drive voltage and the phase of the output of at least one modulator is shiftable. The split signals are recombined by an optical recombiner ( 12 ) to form an optical phase shift key output. The arrangement further comprises a phase modulator ( 20 ) adapted to chirp the optical phase shift key output.
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