Passive optical repeater bypass for optical fiber systems

A data transmission system that comprises an optical fiber transmission line and at least first and second repeaters that receive incoming optical information signals from the transmission line, wherein the second repeater is situated downstream of the first repeater with respect to a data stream in the transmission line, the second repeater includes means for collecting data from a sensor and injecting said data into said data stream, and each of the first and second repeaters comprises means for generating and amplifying electrical information signals in response to said incoming signals, generating outgoing optical signals in response to said electrical information signals, and injecting said outgoing signals into the transmission line, the first repeater comprising:

• a) a receiver for generating and amplifying the electrical information signals;
• b) a clock recovery unit for receiving the electrical information signals from the receiver and re-timing digital data within said signals, said unit comprising a local clock source for generating, on demand, a system startup frame that will enable the second repeater to continue to operate in the event that there is a fault in the transmission line upstream of the first repeater;,
• c) a laser transmitter for receiving said signals after they have been processed by the clock recovery unit, and for generating the outgoing optical signals;
• d) a bypass line for directing a portion of the incoming optical signals into the transmission line as outgoing optical signals without conversion of said portion to electrical signals;
• e) a power supply electrically connected to the receiver, clock recovery unit, and transmitter;
• f) a monitor distinct from, and electrically connected to the power supply, receiver, clock recovery unit, and transmitter;
• and
• g) passive optical coupling means for receiving outgoing optical signals from the laser transmitter and the bypass line, coupling a portion of said outgoing optical signals into the transmission line, and diverting a portion of said outgoing optical signals directly into the monitor, wherein:
• h) the monitor includes control means for making transitions from one to another of respective internal states selected from a plurality of states, said plurality including a NORMAL state, a DISABLE state, and a STARTUP state;
• i) the first repeater includes means for turning off the laser transmitter when the DISABLE state is entered;
• j) the control means are adapted to make a transition from the NORMAL state to the DISABLE state when the monitor receives a faulty diagnostic signal from the receiver, the clock recovery unit, or the power supply;
• k) the control means are further adapted to make a transition from the DISABLE state to the STARTUP state when the optical input to the monitor from the passive optical coupling means drops below a threshold;
• and
• l) means, activated when the STARTUP state is entered, for causing the clock recovery unit to generate a system start-up frame using the local clock source, and for transmitting said start-up frame, whereby at least the second repeater is allowed to operate.