Patent ID: 9509411
Filing Date: 2016-11-29
CPC Classification: H04B

Claim Text:
1. A phase shift keying optical modulation apparatus comprising: an optical phase shifting apparatus arranged to receive an optical carrier signal and arranged to selectively apply a preselected optical phase shift to the optical carrier signal in dependence on a symbol of a 2N-level phase shift keying modulation format to be encoded onto the optical carrier signal; and an optical modulator arranged to receive the optical carrier signal from the optical phase shifting apparatus and arranged to apply a phase modulation to the optical carrier signal in dependence on the symbol, the phase modulation being a phase-modulation of an N-level phase shift keying modulation format, to thereby encode the symbol onto the optical carrier signal, a first optical path arranged to apply a first phase shift to the optical carrier signal; a second optical path comprising an optical phase shifter arranged to apply the reselected optical phase shift, relative to the first optical phase shift, to the optical carrier signal; and an optical switch arranged to receive the optical carrier signal and arranged to selectively route the optical carrier signal into one of the first optical path and the second optical path; and wherein the phase shift keying optical modulation apparatus further comprises a controller arranged to generate and transmit to the optical switch a control signal arranged to cause the optical switch to route the optical carrier signal in dependence on the symbol, and arranged to generate and transmit to the optical modulator a drive signal arranged to cause the optical modulator to apply the phase-modulation to the optical signal, to thereby encode the symbol onto the optical carrier signal.