Methods and Apparatus for Detecting a Fault in an Optical Communication Network

A remote unit for communication with a main unit in an optical communication network, wherein the main unit and the remote unit are configured to detect a fault in the optical communication network, the remote unit comprising:

• a modulation converter configured to receive a first optical signal from the main unit on the optical communication network, wherein the first optical signal has a first modulation type;
• wherein the modulation converter is configured to convert the first optical signal having the first modulation type to a second optical signal having a second modulation type, wherein the second modulation type is different to the first modulation type;
• wherein the modulation converter is a passive device;
• and
• wherein the remote unit is configured to send the second optical signal having the second modulation type to the main unit using the optical communication network.

A main unit for communication with a remote unit in an optical communication network, wherein the main unit and the remote unit are configured to detect a fault in the optical communication network, the main unit comprising:

• processing circuitry;
• and
• memory containing instructions executable by the processing circuitry whereby the main unit is operative to:
• transmit a first optical signal from the main unit on the optical communication network, wherein the first optical signal has a first modulation type;
• receive an optical signal from the remote unit;
• and
• identify a presence of a second optical signal in the received optical signal to detect a fault in the optical communication network;
• the second optical signal having a second modulation type on the optical communication network, wherein the second modulation type is different to the first modulation type.

A method, in a remote unit, for communicating with a main unit in an optical communication network, wherein the main unit and remote unit are configured for detecting a fault in the optical communication network, the method comprising the remote unit:

• modulation converting a first optical signal received from the main unit on the optical communication network, wherein the first optical signal has a first modulation type;
• wherein the modulation conversion converts the first optical signal having the first modulation type to a second optical signal having a second modulation type, wherein the second modulation type is different to the first modulation type;
• wherein the modulation converting uses a passive device;
• and
• sending the second optical signal having the second modulation type to the main unit using the optical communication network.

A method in a main unit for communicating with a remote unit in an optical communication network, wherein the main unit and remote unit are configured for detecting a fault in the optical communication network, the method comprising the main unit:

• transmitting a first optical signal from the main unit on the optical communication network, wherein the first optical signal has a first modulation type;
• receiving an optical signal from the remote unit;
• and
• identifying a presence of a second optical signal in the received optical signal to detect a fault in the optical communication network;
• the second optical signal having a second modulation type on the optical communication network, wherein the second modulation type is different to the first modulation type.