PURPOSE: To improve discrimination capability, by allowing a filter, which is inserted to a transmission line to be tested, to transmit the light of a wavelength for signal transmission through but reflect lights of wavelengths for monitor other than said light.
CONSTITUTION: A filter 2 which transmits the light of a wavelength for signal transmission through but reflects lights of other wavelengths is inserted to the end part of an optical transmission line 1. The light of a wavelength for signal transmission is transmitted to the transmission line 1 and passes through the filter 2 and is converted to an electric signal by a photoelectric converter 3 and is subjected to the signal processing, and meanwhile, the light of a wavelength for monitor which is not used for signal transmission is incident to the transmission line 1 and is reflected by the filter 2 and is returned to a light receiving device 6. The time from the incidence of this light to the return to the device 6 and the reflection quantity are measured to calculate the distance from the incidence end to the filter 2 and the reflectance; and thus, the reflectance of the filter 2 for the light of a wavelength to be reflected is set to 100% approximately to detect the break of the transmission line 1 on the basis of the measurement of the reflection quantity.
MINOWA JIYUNICHIROU
SATOU KENICHI
| JPS53130053A | 1978-11-13 |