Optical sender and method for deciding modulation timing correctness

A method for deciding whether modulation timing correctness in an optical sender that modulates an optical pulse train having a predetermined period for data sending, the method comprising:

• by a first modulator, performing intensity modulation on the optical pulse train to output a first optical pulse train, wherein the intensity modulation is performed at least between a reference intensity and a zero intensity;
• by an asymmetric interferometer, inputting the first optical pulse train and outputting a second optical pulse train of double pulses, wherein each double pulse is generated by temporally separating each optical pulse of the first optical pulse train;
• by a second modulator, performing send-data modulation for each pulse pair of the second optical pulse train to output a third optical pulse train;
• by an optical intensity measuring device, measuring an optical intensity of the third optical pulse train;
• and
• by a controller,
• a) controlling the intensity modulation of the first modulator
• for generating each double pulse of the second optical pulse train having the reference intensity or the zero intensity depending on the intensity modulation according to an intensity modulation pattern;
• b) controlling the send-data modulation of the second modulator for generating each pulse pair of the second optical pulse train with either pulse of the pulse pair having the zero intensity depending on the send-data modulation according to a send-data modulation pattern;
• and
• c) deciding whether or not the pulse pair is the double pulse, based on an optical intensity of the third optical pulse train when changing either of the intensity modulation pattern and the send-data modulation pattern.

A non-transitory computer readable storage medium storing a program for functioning a computer as a controller of an optical sender including:

• a first modulator that performs intensity modulation on the optical pulse train to output a first optical pulse train, wherein the intensity modulation is performed at least between a reference intensity and a zero intensity;
• an asymmetric interferometer that inputs the first optical pulse train and outputs a second optical pulse train of double pulses, wherein each double pulse is generated by temporally separating each optical pulse of the first optical pulse train;
• a second modulator that performs send-data modulation for each pulse pair of the second optical pulse train to output a third optical pulse train;
• and an optical intensity monitor that measures an optical intensity of the third optical pulse train,
• the program which, when executed by a processor of the optical sender, performs a method comprising:
• a) generating each double pulse of the second optical pulse train having the reference intensity or the zero intensity depending on the intensity modulation according to an intensity modulation pattern;
• b) generating each pulse pair of the second optical pulse train with either pulse of the pulse pair having the zero intensity depending on the send-data modulation according to a send-data modulation pattern;
• and
• c) deciding whether or not the pulse pair is the double pulse, based on an optical intensity of the third optical pulse train when changing either of the intensity modulation pattern and the send-data modulation pattern.