According to the present invention, there is provided apparatus for providing protection of an optical link. The apparatus comprises a first port for coupling to the optical link and a second port for coupling to a further optical link. The apparatus further comprises a third port configured to receive an upstream optical signal to be transmitted over the optical link, and to output a downstream optical signal received over the optical link. The apparatus further comprises protection switching apparatus operable to selectively couple the third port to the first port or to the second port. The apparatus further comprises modifying apparatus configured to modify the upstream optical signal, received at the third port, before it is output from the first port, such that the switching upstream optical signal has a distinctive physical characteristic. The apparatus further comprises detecting apparatus, coupled between the first port and the third port, configured to receive a portion of an incoming optical signal, received at the first port, and to selectively detect the presence of the upstream optical signal or the downstream optical signal in the portion of the incoming signal based on the distinctive physical characteristic. The apparatus further comprises control circuitry configured to provide a control signal to the protection switching apparatus based on an output from the detecting apparatus.

A cluster of optronic modules includes an optronic circuit comprising a printed circuit formed by an insulating plate having conductive tracks; and optronic modules. The optronic modules include metal pins comprising at least one digital signal input/output pin, a ground pin and a power supply pin; and at least one optical connector for the input/output of a bidirectional light signal.

Assemblies include a micronode having an optical connector, a coaxial connector port and a housing that includes a plurality of mounting bores. The assembly further includes a filter having a housing that underlies the micronode housing, the filter housing including a plurality of mounting bores, the mounting bores of the filter housing aligning with the mounting bores of the micronode housing. The filter further includes a first optical connector configured to receive an optical drop cable, a second optical connector configured to receive an optical cable and an optical pigtail cord that is connected to the optical connector of the micronode.

A node in a wavelength division multiplexing (WDM) system is provided, which includes: a colorless optical transmitter, a first arrayed waveguide grating, a first waveband filter configured to divide an input optical signal into M sub-signals of different wavebands and output to a first optical switch, and a first optical coupler/a first optical combiner. A transmit end of the colorless optical transmitter is coupled to an input end of the first waveband filter via the first arrayed waveguide grating. The first optical switch is configured to connect an output end of the first waveband filter to an input end of the first optical coupler/the first optical combiner according to a control signal. An output end of the first optical coupler/the first optical combiner is coupled to an optical transmission path.

Methods, systems, and apparatus, for an external cavity FP laser. In one aspect, an apparatus is provided that includes a FP laser diode; a Faraday rotator (FR) coupled to receive an optical output of the FP laser diode and that rotates a polarization of the optical output; an optical fiber coupled at a first end to receive the output of the FR; a WDM filter coupled to a second end of the optical fiber to receive the optical signal from the optical fiber; and a FRM coupled directly or indirectly to an output of the WDM filter, wherein an optical output of the WDM filter is partially reflected by the FRM such that the polarization of a reflected beam is rotated, and wherein the reflected optical signal then passes through the FR with its polarization being rotated by the FR before it is injected back into the FP laser diode.

In an example embodiment, a WDM array includes an optical filter, N common ports, N reflection ports, and N pass ports. The N common ports may be positioned to a first side of the optical filter. N may be greater than or equal to two. The N reflection ports may be positioned to the first side of the optical filter. The N pass ports may be positioned to a second side of the optical filter opposite the first side.

A method and system for selective and per-node XPM compensation may separate wavelengths into short traveling wavelengths (STW) and long traveling wavelengths (LTW) based on transmission distance over their respective optical paths. XPM compensation at ROADM nodes may be selectively performed for the LTW, while the STW may be passed through without XPM compensation, among other functionality at the ROADM nodes.

A method and system for multi-channel optical XPM compensation may include a DCM to improve performance of a feed-forward control loop in an optical path in an optical network. Additionally, various spectral overlap schemes may be used with multi-channel WDM optical signals using XPM compensators in parallel, such as at a ROADM node. Polarization diversity may also be supported for XPM compensation including a DCM.

We disclose a transceiver module having two optical transceivers, each connectable to a different respective optical line, and a pluggable electrical connector that can be mated with a matching electrical connector in a connection slot of the host network device. The transceiver module also has an electrical interface circuit that can transfer data between the optical transceivers and the host network device in a manner that provides a route for transferring data between two optical transceivers without crossing the electrical connectors. This architecture advantageously enables the optical-line rates to not be limited by the electrical data rate of data transfer through the electrical connectors. In some embodiments, the transceiver module is configurable in a manner that can change the optical-line rates of the optical transceivers and/or the electrical data rate. The latter feature enables the transceiver module to be compatible with both older and newer network devices.

An optical remodulator includes: a polarization diversity modulator configured to modulate an input optical signal to generate an output optical signal by using a first optical modulator implemented for a first polarization state and a second optical modulator implemented for a second polarization state that is orthogonal to the first polarization state; a photo detector configured to optical-to-electrical convert the input optical signal or the output optical signal or both of the optical signals into an electric signal; and a drive signal generator configured to generate a first drive signal that drives the first optical modulator and a second drive signal that drives the second optical modulator based on the electric signal generated by the photo detector.