Patent ID: 8315516

Claim:
A signal transmitter comprising: a main transmission line-transmitting portion that transmits optical signals through a plurality of main transmission lines; a backup transmission line-transmitting portion that transmits the optical signals through backup transmission lines paired with the main transmission lines; a selector that selects a transmission line to be used for transmitting the optical signals from any of the transmission lines through which the optical signals are transmitted by the main transmission line-transmitting portion and the backup transmission line-transmitting portion; a control signal transmission portion that transmits a first control signal to a signal receiver through a first control line different than the plurality of main transmission lines and backup transmission lines; a control signal reception portion that receives a second control signal from the signal receiver through a second control line different than the plurality of main transmission lines and backup transmission lines; and a controller that, in response to the second control signal indicating that a fault has occurred on at least one of the main transmission lines, sends the first control signal identifying a switching command to the signal receiver, and outputs the switching command to the selector, based on information received in the second control signal identifying the main transmission line with the fault which is received from the signal receiver receiving the optical signals, which causes the main transmission line-transmitting portion to stop transmitting the optical signals to the main transmission line with the fault, while causing the backup transmission line-transmitting portion to transmit the optical signals being transmitted to the main transmission line with the fault to the backup transmission lines.