Optical signal processing device and method for controlling same
An optical signal processing device is described herein for reducing electric wirings in an optical switch or an optical filter realized using an optical waveguide. The optical signal processing device includes an optical waveguide formed on a substrate. In the optical signal processing device, the optical waveguide includes at least one input port and at least one output port, a plurality of driven elements are provided including a phase shifter that produces a phase shift to an optical signal from the input port, each of the driven elements includes at least two control terminals, control wirings are provided to have control signals being time-division synchronized applied between the two control terminals, and the control wiring for accessing the driven element is shared by the plurality of driven elements.
1. A method of controlling an optical signal processing device, the optical signal processing device comprising:
an optical waveguide formed on a substrate, the optical waveguide including at least one input port and at least one output port; and
a plurality of driven elements including a phase shifter, the phase shifter producing a phase shift to an optical signal from the input port,
each of the driven elements including
two control terminals, and
control wirings provided to have control signals applied between the two control terminals, the control signals being time-division synchronized, wherein any of the control wirings for accessing the driven element is shared by the plurality of driven elements,
the method comprising:
applying the control signals to the two control terminals, each of the control signals is a time division control signal having a time waveform being time-division synchronized in a predetermined time slot, the time waveform being repeated in a predetermined pattern over a plurality of switching cycles T, the switching cycle T including a plurality of time slots; and
addressing any of the plurality of driven elements according to the control signals,
wherein a modulation format of the optical signal is a quadrature amplitude modulation signal, and a relation ψ<θ is established, wherein θ is defined as a phase difference corresponding to a distance between respective symbol points of the quadrature amplitude modulation signal and ψ is defined as a residual fluctuation component at a switching frequency fs (=1/T) of the time division control signal in a frequency response of the phase shifter.
2. The method of controlling the optical signal processing device according to claim 1 , wherein
the switching cycle T of the time division control signal is shorter than a time constant τ of the phase shifter.