| 摘要 |
PURPOSE:To improve the efficiency in measuring an optical fiber cable by setting the frequency of the local oscillator of the reception unit before the arrival of the modulated wave of the corresponding frequency, and automatically and stepwisely setting the local oscillator to the subsequent frequencies after detecting said modulated wave. CONSTITUTION:The transmission end of an optical fiber 3 is provided with a sweep-type signal generator 1 and a laser source 2. The RF output signal from the signal generator 1 optically modulates the laser source 2, and the optically modulated wave is made incident on the optical fiber 3 being measured. At the reception end of the optical fiber 3, an out going ray of light is converted into electricity in a light detector 4, and the optically modulated wave component is detected. The frequency of the output of the detector 4, which varies with the lapse of sweep time, is detected and outputted only when the signal of the frequency determined according to the local-oscillated frequency f1 and the intermediate frequency is inputted to a heterodyne detector 6. Then, in the similar manner, the local-oscillated frequency is discretely varied, and the detection output and the local-oscillated frequency are recorded on a display 10. |
