Patent ID: 7064840

Claim:
An optical sampling method for monitoring repeatedly entered high speed signal lights, comprising the steps of: generating optical pulses with an optical pulse width shorter than an inverse of a frequency variation of the signal lights, which has a period slightly different from a repetition period of the signal lights, from an optical pulse generation unit; splitting each of the signal lights and the optical pulses into two parts by respective splitters; delaying a split part of either the signal lights or the optical pulses for a prescribed period of time by a delay unit; inputting one split part of the signal lights and one split part of the optical pulses into a first optical hybrid, while inputting the delayed split part of the signal lights or the optical pulses and the other split part of either the signal lights or the optical pulses whichever was not delayed into a second optical hybrid; receiving output lights from the first optical hybrid at first and second balanced optical receivers, and outputting first and second currents; receiving output lights from the second optical hybrid at third and fourth balanced optical receivers, and outputting third and fourth currents; and obtaining a frequency modulation component of the signal lights by calculation processing using values of the first to fourth currents by a calculation processing device.