METHODS AND DEVICES FOR ALTERING OPTICAL POLARISATION

摘要

A23567 OPTICAL POLARISATION CONTROL The invention provides methods and devices for processing an optical signal. In one embodiment an optical device (101) for scrambling an Input optical signal comprises an optical switch (10) which switches the optical signal between two intermediate optical paths (13,14) under control of a scrambling signal from A control circuit (12). The polarisation of the signal in one of the intermediate optical paths (13) is rotated by a TE-TM converter (15). The polarisations of the two intermediate signals are thereby made mutually orthogonal. These mutually orthogonal signals are then recombined by a directional coupler (16) to provide a combined output optical signal with a scrambled polarisation alternating between othogonal states according to the frequency of the scrambling signal. The invention may be applied to improve signal reception, for example, in coherent optical transmission systems. Figure 3