| 摘要 |
PROBLEM TO BE SOLVED: To prevent the deterioration of a signal level and an SN ratio with a long distance call by making an analog sound signal into a pulse, converting it into an optical pulse signal by a light transmitter, transmitting it through one optical fiber, converting the optical pulse signal received in an optical coupler through the same optical fiber into an analog electric signal by a light receiver and interrupting a high pass frequency component. SOLUTION: A sound signal inputted by a microphone 1 becomes a pulse modulation signal by a pulse width modulator 5 and it is converted into an optical pulse signal by the light transmitter 6. The optical pulse signal is transmitted to the optical fiber 14 through the optical coupler 7. The optical pulse signal from an opposite party is received in the optical coupler 7 and it is converted into the analog electric signal by the light receiver 8. A high band interruption filter 9 interrupts the high frequency component of the analog electric signal for more than audible sound. Information is transmitted while placing it on the width of the pulse, a repetitive frequency and a position. Since the signals of transmission and reception are separated in the optical coupler, bi-directional communication is realized by one optical fiber. |
