| 摘要 |
PURPOSE:To improve the reliability and to reduce the cost by distributing a part of an optical signal at a subscriber side, reflecting the residual optical signal as it is and modulating a data signal from the subscriber side so as to eliminate the need for an E/O converter having been provided on the subscriber side. CONSTITUTION:As soon as a data sent from a terminal station is modulated by a signal whose center frequency is f1, a light illuminated from a light emitting element 3 by a signal having a frequency f2 different from the frequency f1 is luminance-modulated, and the subscriber side distributes a part of the light and extracts only the signal of the frequency f1 and demodulates a data from the terminal station side. The residual light not distributed is reflected as it is at the terminal station side, a data signal from the subscriber side is modulated, the result is sent to the terminal station side, the terminal station side extracts the signal of the frequency f2 and it is demodulated and the data from the subscriber side is extracted. Thus, even when a light emitting element (E/O converter) having been installed to the subscriber side is eliminated, the optical fiber bidirectional transmission is implemented and the reduction in cost is remarkably attained. |
