Patent ID: 9122084
Filing Date: 2015-09-01
Classification: G02F,H04B

Abstract:
1. A phase modulation apparatus comprising: a light source which outputs continuous light having a constant optical phase; a first phase modulator and a second phase modulator which modulate respective first and second optical phases of first and second continuous lights, obtained by branching an output of the light source, based on first and second electrical data signals, respectively; a π/2 phase shifter which shifts the optical phase of an output of one the first and second phase modulators by π/2; a multiplexer which combines an output of the π/2 phase shifter and an output of the other one of the first and second phase modulators to provide a combined light output; an intensity modulator which intensity-modulates the combined light output of the multiplexer with an electrical clock signal synchronized with at least one of the first and second electrical data signals; a first and a second phase shifter which are disposed in one of (a) first and second electrical paths, respectively, through which the first and second electrical data signals propagate to the first and second phase modulators, respectively, (b) said first electrical path and a third electrical path through which the electrical clock signal propagates to the intensity modulator, and (c) said second and third electrical paths, and which shift the Phase of at least one of the first and second electrical data signals or the phase of the electrical clock signal; and a phase control circuit which controls, based on the phase of the first and second electrical data signal or the phase of the electrical clock signal in the electrical path in which a phase shifter is not disposed, the phase of the first and or second electrical data signal or the phase of the electrical clock signal in the electrical path in which the phase shifter is disposed so that the intensity of the optical output from the intensity modulator is maximum.