| 摘要 |
<p>PURPOSE:To easily remove excessive Fresnel reflecting light and unnecessary back scattering signal component to prevent the deterioration of the characteristics of an electric circuit by using light frequencies for measurement, locality and dummy, and most suitably establishing these three kinds of light frequencies. CONSTITUTION:A pattern generator 13 generates signals P2 for a dummy, and a composing device 14 composes them to issue composite signals PP having the values of voltages V1-V3 for generating signal lights L1-L3 for measurement, locality and dummy. A frequency modulating circuit 15 gives frequency shift proportional to each of the voltages V1-V3 to a light source 3. An optical heterodyne detection is executed on signal lights L1-L3 having these three values to obtain a beat signal SO' composed of the three kinds of frequency components. The beat signal, after optical detection, obtained by back scattering light and signal light for locality which are based on the signal light L1 for measurement is then taken out of the obtained beat signals SO' for measuring the back scattering light.</p> |
