Abstract: A system and method including a parity bit encoder for encoding each n bits of data to be transmitted with a parity check bit to produce blocks of n+1 bits (n information bits plus one parity bit associated with the n information bits). Each of the blocks of n+1 bits are Gray mapped to a plurality of associated QAM symbols that are modulated onto an optical wavelength and transmitted to a receiver. A maximum a posteriori (MAP) decoder is used at the receiver to correct for cycle slip. Phase errors of 180 degrees may be detected by independently encoding odd and even bits prior to Gray mapping, and identifying errors in decoding odd numbered bits at the receiver.

Abstract: A repeater that enables both bi-directional optical time domain reflectometry (OTDR) and loop gain monitoring techniques that may be employed, for example, in particularly long repeater spans. In one embodiment, the repeater includes high loss loopback (HLLB) paths configured to couple test signals between incoming and outgoing fiber paths. The HLLB paths are coupled from the outputs to the inputs of amplifiers within the repeater and couple both OTDR and loopback signals from an outgoing fiber path to an incoming fiber path so that may be returned to line monitoring equipment that transmitted the test signals.

Abstract: A multiple conductor optical cable may be coupled to an undersea device, such as a cable joint, branching unit, or repeater, with one or more isolated bypass conductive paths being provided across the undersea device. At least one conductor may be terminated within a housing of the undersea device and at least one conductor may be coupled to a conductive bridge member that provides the isolated bypass conductive path across the device. Multiple conductor optical cables may be coupled to undersea devices in optical networks using independent power paths, for example, to deliver power to different powered components at different voltage potentials.