Patent ID: 8401398

Claim:
A frequency-shift keying modulator for optical communications comprising: a first interferometer having a first arm with a first electro-optic modulator and a second arm, the first and second arms of the first interferometer having a differential delay therebetween that is modulated by the first electro-optic modulator in response to a first control signal having a time-dependent signal value determined according to a communications signal to be transmitted; and a second interferometer in optical communication with the first interferometer and having a first arm with a second electro-optic modulator and a second arm, the first and second arms of the second interferometer having a differential delay therebetween that is modulated by the second electro-optic modulator in response to a second control signal that has a time-dependent signal value determined according to the communications signal to be transmitted, the differential delay of the second interferometer being one-half the differential delay of the first interferometer, the second control signal having a number of time-dependent signal values that is twice a number of time-dependent signal values of the first control signal, wherein a tone of a multi-tone optical signal received at one of the interferometers is selected for transmission through the first and second interferometers according to the time-dependent signal values of the first and second control signals.