An optical network device receives an optical signal, to which polarization information is added, from a transmitter via a transmission line. The receiver generates electric-field-information signal of the optical signal. The processor acquires, for respective polarization rotation amounts, the electric-field-information signal during a period specified by the polarization information. The processor calculates, for respective polarization rotation amounts and based on the electric-field-information signal, evaluation values corresponding to powers of the optical signal at a plurality of positions on the transmission line. The processor calculates, for respective positions, variations in the evaluation values corresponding to the polarization rotation amounts. The processor output information that indicates a first position when the variation in the evaluation values for the first position is larger than that for a second position where the second position is adjacent to the first position on a transmitter side.

An optical network device receives an optical signal, to which polarization information is added, from a transmitter via a transmission line. The receiver generates electric-field-information signal of the optical signal. The processor acquires, for respective polarization rotation amounts, the electric-field-information signal during a period specified by the polarization information. The processor calculates, for respective polarization rotation amounts and based on the electric-field-information signal, evaluation values corresponding to powers of the optical signal at a plurality of positions on the transmission line. The processor calculates, for respective positions, variations in the evaluation values corresponding to the polarization rotation amounts. The processor output information that indicates a first position when the variation in the evaluation values for the first position is larger than that for a second position where the second position is adjacent to the first position on a transmitter side.

An echo cancellation method includes steps of (a) extracting phase-distortion estimates, (b) reconstructing an echo signal, (c) generating a clean signal, and (d) producing a primary signal. Step (a) includes extracting, from a first phase signal, a plurality of phase-distortion estimates, the first phase signal having been estimated from an echo-corrupted signal received at a first coherent transceiver of a coherent optical network. Step (b) includes reconstructing an echo signal from the plurality of phase-distortion estimates and a transmitted signal transmitted by the first coherent transceiver. Step (c) includes generating a clean signal as a difference between the reconstructed echo signal and the first phase signal. Step (d) includes producing a primary signal by mapping each of a plurality of clean-phase estimates of the clean signal to one of a plurality of constellation symbols associated with a modulation scheme of the primary signal.

A polarization scrambler using a retardance element (RE) is disclosed. The polarization scrambler may include an optical fiber input to transmit an optical signal, and a beam expander to receive and expand the optical signal to create an expanded optical signal. The polarization scrambler may include a retardance element (RE) to cause a polarization scrambling effect on the expanded optical signal and to create a scrambled expanded optical signal. The polarization scrambler may include a beam reducer to receive and reduce the scrambled expanded optical signal to create a scrambled optical signal. The polarization scrambler may include an optical fiber output to receive scrambled optical signal. The optical fiber output may transmit the scrambled optical signal to one or more downstream optical components.

Provided is an optical transmission method including: executing mapping processing (112) so that information of one unit of one system, or one unit of each of a plurality of systems, is mapped in a pattern of two or more Stokes vectors orthogonal between slots of a multi-time slot; generating an optical signal from an electric signal processed by the mapping processing; and transmitting the optical signal. A reception side receives the optical signal and converts the received optical signal into an electric signal, and executes de-mapping processing (322) for conversion into the information of one unit of one system, or one unit of each of a plurality of systems, by selecting high-likelihood bit information in association with the mapping processing in which the information is mapped in the pattern of Stokes vectors orthogonal between the slots of the multi-time slot.

A full duplex communication network includes a first coherent optics transceiver having (i) a first receiver, and (ii) a first transmitter configured to transmit a first dual polarized signal. The network further includes a second coherent optics transceiver having (i) a second receiver configured to receive the first dual polarized signal, and (ii) a second transmitter configured to transmit a second dual polarized signal. The network further includes an optical transport medium operably coupling the first coherent optics transceiver to the second coherent optics transceiver, and a first compensation module configured to filter (i) crosstalk between orthogonal components of the first dual polarized signal, and (ii) reflections between the first dual polarized signal and the second dual polarized signal.

An optical transceiver includes: a receiver and a processor. The receiver receives a polarization multiplexed optical signal that includes a first polarization signal and a second polarization signal so as to output reception electric-field information that indicates an electric field of the polarization multiplexed optical signal. The processor calculates, according to the reception electric-field information, a variation monitor value that indicates an amount of leakage of signal components between the first polarization signal and the second polarization signal. When the variation monitor value exceeds a specified threshold, the processor analyzes, according to the reception electric-field information, a state of an optical transmission line through which the polarization multiplexed optical signal propagates.

A hybrid optical transceiver is provided. An optical component disposed on a substrate, the optical component comprising a transmitter section and a receiver section. Transmitter section comprises a plurality of vertical cavity surface emitting laser (VCSEL) arrays communicatively coupled to a plurality of multiplexers, configured to launch multiplexed optical signals into the lowest order mode group of a multimode fiber or the lowest order mode of a single mode fiber. Receiver section comprises a photodetector array comprising a plurality of optical detectors, and configured to receive demultiplexed optical signals of unknown polarization without routing waveguides. In various embodiments, each section being independently removable from a substrate.

An optical communication apparatus includes a first monitor that monitors a first signal carried on a first polarization and outputs a first monitor value representing a transmission characteristic of the first signal, a second monitor that monitors a second signal carried on a second polarization orthogonal to the first polarization and outputs a second monitor value representing a transmission characteristic of the second signal, and a transmitting circuit that notifies a transmitting source of the first signal and the second signal of the first monitor value and the second monitor value.

An integrated optical device includes: a housing; a liquid-crystal optical power attenuator, an optical splitter, and an optical power monitor housed inside the housing; and first and second optical fibers housed inside the housing. The first optical fibers input an optical signal from outside the housing to the optical power attenuator. In a polarized state, the optical power attenuator attenuates the optical signal from the first optical fibers. The second optical fibers output the attenuated optical signal from the optical power attenuator to outside the housing. The optical splitter generates a split signal by splitting at least one of: the optical signal input to the optical power attenuator from the first optical fibers, and the attenuated optical signal propagated from the optical power attenuator to the second optical fibers. The optical power monitor receives the split signal and detects a power of the split signal.