PROBLEM TO BE SOLVED: To generate optical pulses whose optical wavelength differs very slightly between adjacent optical pulses. ;SOLUTION: A DC power supply 12 supplies a DC current for oscillation of continuous laser to a semiconductor laser 10 and simultaneously a high frequency oscillation circuit 14 supplies a sine wave AC current whose frequency is fs (e.g. 10MHz) to the semiconductor laser 10. The amplitude of the output light from the laser 10 is fluctuated at a period of 1/fa by the AC drive from the high frequency oscillation circuit 14 and the wavelength is fluctuated at a period of 1/fa within a prescribed optical wavelength range. An optical modulator 16 absorbs a laser beam outputted from the semiconductor laser 10 continuously with a clock frequency fb (e.g. 10GHz) selectively to generate optical pulses at a period of 1/fb with a prescribed pulse width (e.g. 15ps). The optical pulse train outputted from the optical modulator 16 differs slightly from the optical wavelength between adjacent optical pulses.;COPYRIGHT: (C)1997,JPO
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