A system and method including polarization modulation of supervisory signals for reducing interference with data signals in a wavelength division multiplexed optical communication system. At least one supervisory signal for monitoring a transmission path and/or elements coupled to the transmission path is fast polarization modulated and launched with data signals onto the path. Polarization modulating of the supervisory signal reduces impact of the supervisory signal on the data signals and improves system performance.

Methods, systems, and devices for network communications to reduce optical beat interference (OBI) in upstream communications are described. For example, a fiber node may provide a seed source to injection lock upstream laser diodes. Therefore, upstream communications from each injection locked laser diode may primarily include the wavelength associated with each seed source. The seed sources may be unique to each end device and configured to minimize OBI. That is, the upstream laser diodes may be generic, but the collected seed source may enable upstream communications at varying wavelengths. The end device may provide upstream communications by externally modulating a signal generated by the injection locked laser diode.

Methods, systems, and devices for network communications to reduce optical beat interference (OBI) in upstream communications are described. For example, a fiber node may provide a seed source to injection lock upstream laser diodes. Therefore, upstream communications from each injection locked laser diode may primarily include the wavelength associated with each seed source. The seed sources may be unique to each end device and configured to minimize OBI. That is, the upstream laser diodes may be generic, but the collected seed source may enable upstream communications at varying wavelengths. The end device may provide upstream communications by externally modulating a signal generated by the injection locked laser diode.

An optical receiver that includes an input port configured to receive intensity modulated optical signal with multipath interference (MPI); a detector configured to convert the intensity modulated optical signal with multipath interference to an electrical signal; a high pass filter (HPF) configured to filter the electrical signal and suppress carrier-carrier beat noise induced by the MPI to produce a filtered electrical signal; and an output port configured to transmit the filtered electrical signal.

A transceiver separates wavelength-division-multiplexing (WDM) components into two groups, one of which is more sensitive to temperature than the other group. The temperature-sensitive group of optical components is implemented on a first substrate in the transceiver that has a lower thermo-optic coefficient than a second substrate in the transceiver, which contains the group of optical components that is less temperature sensitive. In particular, the first substrate, which may be glass, may include WDM components that convey optical signals having multiple carrier wavelengths. Moreover, the second substrate, such as a silicon substrate (e.g., a silicon-on-insulator platform), may include multiple parallel optical paths with optical components, in which a given optical path conveys an optical signal having a given carrier wavelength.

A transceiver separates wavelength-division-multiplexing (WDM) components into two groups, one of which is more sensitive to temperature than the other group. The temperature-sensitive group of optical components is implemented on a first substrate in the transceiver that has a lower thermo-optic coefficient than a second substrate in the transceiver, which contains the group of optical components that is less temperature sensitive. In particular, the first substrate, which may be glass, may include WDM components that convey optical signals having multiple carrier wavelengths. Moreover, the second substrate, such as a silicon substrate (e.g., a silicon-on-insulator platform), may include multiple parallel optical paths with optical components, in which a given optical path conveys an optical signal having a given carrier wavelength.

An example apparatus includes a mode selective detector, a measurement module, a difference calculator and a threshold and alarm module. The mode selective detector detects a plurality of modes of a spatially multiplexed signal. The measurement module measures a parameter for the plurality of modes of the spatially multiplexed signal, wherein the parameter is a power or a signal to noise ratio (SNR). The difference calculator compares the measured parameter among a subset modes and/or among a known set of unperturbed parameters and determines a differential, the subset including at least one mode. The threshold and alarm module sets an alarm indicator when the differential is out of bounds.

An example apparatus includes a mode selective detector, a measurement module, a difference calculator and a threshold and alarm module. The mode selective detector detects a plurality of modes of a spatially multiplexed signal. The measurement module measures a parameter for the plurality of modes of the spatially multiplexed signal, wherein the parameter is a power or a signal to noise ratio (SNR). The difference calculator compares the measured parameter among a subset modes and/or among a known set of unperturbed parameters and determines a differential, the subset including at least one mode. The threshold and alarm module sets an alarm indicator when the differential is out of bounds.

A simple, compact and low-cost passive optical transceiver device with four terminals may be used in an optical transmission system with polarization-diversity coherent detection scheme. The transceiver is composed of a first polarization splitter/combiner, a non-reciprocal polarization rotator and a second polarization splitter/combiner. The device simultaneously operates as a transmitter and a receiver with optical signals propagating along opposite directions wherein non-reciprocal polarization rotation leads to distinct effects. The received optical signal is thus split into two orthogonal polarization components directed towards two separate ports.

A simple, compact and low-cost passive optical transceiver device with four terminals may be used in an optical transmission system with polarization-diversity coherent detection scheme. The transceiver is composed of a first polarization splitter/combiner, a non-reciprocal polarization rotator and a second polarization splitter/combiner. The device simultaneously operates as a transmitter and a receiver with optical signals propagating along opposite directions wherein non-reciprocal polarization rotation leads to distinct effects. The received optical signal is thus split into two orthogonal polarization components directed towards two separate ports.