Angle modulator

An angle modulator for converting an input modulating signal into an angle-modulated signal through homodyne detection, comprising:

• a light source emitting a light;
• an optical branching part branching the light emitted by said source into a first light and a second light;
• an optical frequency shifter performing frequency conversion or frequency shifting of an optical frequency of said first light for a predetermined amount fc, and outputting as a first optical signal;
• an optical angle modulator performing optical angle modulation on said second light with said input modulating signal, and outputting an optical-angle-modulated signal as a second optical signal;
• an optical coupler coupling said first and second optical signals;
• and
• a photo-detector with a square-law detection characteristic converting an optical signal outputted from said optical coupler into an electrical signal and outputting the electrical signal as said angle-modulated signal having a carrier frequency fc.

A method for converting an input modulating signal into an angle-modulated signal through homodyne detection, comprising the steps of:

• branching light emitted by a light source into a first light and a second light;
• generating a first optical signal including a signal component of an optical frequency shifted from an optical frequency of said first light for a predetermined amount fc;
• generating a second optical signal through optical angle modulation on said second light with the input modulating signal;
• coupling said first optical signal and said second optical signal;
• and
• converting the coupled optical signals into an electrical signal through homodyne detection and outputting said angle-modulated signal having a carrier frequency fc.