Remote monitoring of an optical transmission system using line monitoring signals

An optical transmission system for transmitting optical signals, said system comprising:

• a first terminal and a second terminal;
• optical paths coupled to said first and second terminals;
• and
• one or more repeaters spaced along said optical paths;
• wherein said first terminal generates a first line monitor signal and a second line monitor signal and transmits the first line monitor signal on an optical path and wherein said second line monitor signal is delayed by a round trip delay from the first terminal to a first repeater;
• wherein each of said repeaters generates a return line monitor signal in response to receiving the first line monitor signal and transmits the return line monitor signal on an optical path;
• and
• wherein said first terminal receives the return line monitor signal and demodulates the return line monitor signal with the second line monitor signal.

A terminal for an optical transmission system that comprises one or more repeaters and an optical path coupled to said repeaters and said terminal that transmits a plurality of optical carriers, said terminal comprising:

• a line monitor signal generator circuit coupled to said optical path;
• and
• a line monitor signal receive circuit coupled to said optical path and said line monitor signal generator circuit;
• wherein said line monitor signal generator circuit comprises
• a first and second modulator;
• a first oscillator coupled to said first modulator and a second oscillator coupled to said second modulator;
• a binary pseudo random sequence generator coupled to said first modulator;
• and
• a delay device coupled to said binary pseudo random sequence generator and coupled to said second modulator.