Optical pulse position detecting circuit and an optical pulse generating apparatus and their methods

An optical pulse generating apparatus comprising:

• a light source for outputting an optical signal with a determined wavelength;
• an oscillator for outputting an electric clock signal with a determined frequency;
• a first optical modulator connected to the oscillator for modulating a power of the optical signal with the electric clock signal and outputting a first modulated optical signal;
• a second optical modulator for modulating a power of the first modulated optical signal outputted from the first optical modulator with the electric clock signal and outputting a second modulated optical signal;
• an optical multiplexer for receiving one of the first modulated optical signal inputted to the second optical modulator and the second modulated optical signal outputted from the second optical modulator, outputting a part of a multiplexed optical signal and branching a part of the multiplexed optical signal;
• a photo detector for converting the multiplexed optical signal from the optical multiplexer to an electric signal;
• a phase changing unit for changing a phase of an optical signal;
• and
• a controlling circuit for receiving the electric signal outputted from the photo detector and the electric clock signal outputted from the oscillator, and controlling a phase change amount of the phase changing unit to match a phase of the electric signal and a phase of the electric clock signal.