| 摘要 |
PROBLEM TO BE SOLVED: To sustain a constant frequency for a long time by detecting the phase difference between an external signal and a clock signal for driving an optical modulator and automatically controlling the resonator length, depending on the detected phase difference, such that the repetitive frequency of a laser pulse oscillator is synchronized with that of the external signal. SOLUTION: An optical fiber 1 is pumped by a pumping source 2 through a photocoupler 3 to cause oscillations of continuous light in the forward direction of an optical isolator 5. Laser output is then taken out through an beam splitter 4 and partially fed to a clock extractor 9 through an optical splitter 8. A clock signal from the clock extractor 9 is fed along with an electric signal from a synthesizer 12 passed through a phase shifter 13, to a phase comparator 14 where the phase difference is detected. Depending on the phase difference thus detected, a phased locked loop comprising an electric filter 15 and an electric amplifier 16 controls the resonator length, such that the repetitive frequency of a laser pulse oscillator is synchronized with that of the external signal. |
