A photonic integrated chip device having a common optical edge interface is provided and specifically a device comprising: a photonic integrated circuit (PIC) chip comprising: an optical circuit; and an electrical interface configured to receive electrical signals for controlling the optical circuit; and, a common optical interface side of the PIC chip comprising: at least one input configured to receive light into the PIC chip to the optical circuit; and at least one output configured to convey at least one optical signal from the optical circuit out of the PIC chip, the electrical interface located on one or more electrical interface sides of the PIC chip different from the common optical interface side.

TDM circuitry that includes a rotary multiplexer and a memory circuit is provided. A first rotary multiplexer circuit may receive N-bit wide data in accordance to a time division multiple access (TDMA) scheme. The N-bit wide data includes multiple sets of M-bit wide data. The first rotary multiplexer may rotate these sets of the M-bit wide data. The memory circuit is coupled to the first rotary multiplexer circuit. The memory circuit stores each of rotated set of M-bit wide data. A second rotary multiplexer circuit may read k-th bits of the each of the stored M-bit wide data from the memory circuit and may rotate these k-th bits before outputting these k-th bits serially, where k is an integer having a value greater than 0.

A demultiplexing unit that is provided in an optical device and performs demultiplexing into a plurality of optical signals having wavelengths different from each other includes a plurality of optical filters that are coupled in multiple stages and in which a period of a peak wavelength of a transmission spectrum differs among different stages, a monitoring optical filter coupled to one of the plurality of optical filters, a monitoring photodetector coupled to the output side of the monitoring optical filter, and a plurality of wavelength adjustment units that are provided individually for the plurality of optical filters and the monitoring optical filter and cause wavelength shifts of an equal amount in a same direction.

A method and apparatus are provided. The method includes receiving, at a TE.sub.0 mode add/drop filter, a TE.sub.0 mode optical signal having a first wavelength and a second wavelength, and transmitting, from the TE.sub.0 mode add/drop filter, the TE.sub.0 mode optical signal having the first wavelength and the second wavelength towards a Bragg grating, without converting the TE.sub.0 mode optical signal having the first wavelength and the second wavelength to another mode. The method further includes receiving, at the TE.sub.0 mode add/drop filter, a reflected TE.sub.1 mode optical signal having the first wavelength from the Bragg grating, and transmitting, from the TE.sub.0 mode add/drop filter, the reflected TE.sub.1 mode optical signal having the first wavelength towards a photodetector, without converting the reflected TE.sub.1 mode optical signal having the first wavelength to another mode.

A reconfigurable optical add/drop multiplexer using a wavelength selective switch (WSS) component to multiplex wavelength channels into a wavelength division multiplexed (WDM) signal. When a given channel is dropped, an amplified spontaneous emission (ASE) injection signal is multiplexed as a ghost channel into the WDM signal. The ASE injection channel can mitigate polarization hole burning and can provide a fuller power spectrum density. However, the ASE injection channel also defines a monitoring window. As an optical channel monitor (OCM) monitors the WDM signal, the OCM can detect, within the monitoring window, any underlying characteristic of the given wavelength channel. In this instance in response to the detected characteristic, the WSS component switches from multiplexing the ghost channel into the WDM signal to multiplexing the given wavelength channel into the WDM signal.

Novel tools and techniques are provided for implementing optical frequency spectral optimization in dense wavelength division multiplexing (DWDM) flex grid systems. In various embodiments, based on a determination that one or more gaps of optical spectrum exist in a range of optical spectrum that contains one or more media channels that support transmission of corresponding one or more first signals, a computing system may determine a network wavelength service frequency assignment for shifting frequency of at least one media channel among the one or more media channels to optimize one or more spacings among the one or more media channels in the range of optical spectrum for supporting transmission of one or more second signals; and may cause one or more optical signal devices to shift a center frequency of each of the at least one media channel, based on the determined network wavelength service frequency assignment.

An add-drop network element (100) for an optical communications network. The add-drop network element comprises an optical amplifier (102) having an input port and an output port. The add-drop network element comprises also comprises an optical coupler (104) and an optical splitter (106). The optical coupler (104) comprises an add input port, a through input port and an output port, the output port of the optical coupler (104) being connected to the input port of the optical amplifier. The optical splitter (106) comprising a drop output port, a through output port and an input port, the input port of the optical splitter (106) being connected to the output port of the optical amplifier.

In general, a branching configuration used in a wavelength division multiplexed (WDM) optical communication system, consistent with an embodiment of the present disclosure, includes a branch path with two or more optical paths cross-coupled to each other to provide redundant add and/or drop channel wavelengths to a branch terminal on each cross-coupled path. Accordingly, a fault condition affecting some of the cross-coupled optical paths may occur physically downstream from the cross-coupling, e.g., within a subsea umbilical cable or associated termination equipment. However, so long as at least one of the cross-coupled optical paths remains operational, then branch terminal equipment in the branch terminal may continue to receive channel wavelengths associated with a faulted optical path via an operational optical path by virtue of cross-coupling. Thus, the cross-coupled configuration reduces or otherwise eliminates the necessity of allocating spare optical paths within the subsea umbilical cable.

The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate respective subcarrier frequencies which represent subchannels of an ITU channel to which client signals can be mapped. In one embodiment, subchannels are polarization interleaved to reduce crosstalk. In another embodiment, polarization multiplexing is used to increase the spectral density. Client circuits can be divided and combined with one another before being mapped, independent of one another, to individual subchannels within and across ITU channels. A crosspoint switch can be used to control the client to subchannel mapping, thereby enabling subchannel protection switching and hitless wavelength switching. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of the client circuits mapped to these subchannels across the nodes of a WDM network.

Optical fiber data communications are described. A controller can determine chromatic dispersion of an optical signal that is to be demodulated using coherent detection. The controller can then determine the chromatic dispersion of another optical signal that is to be demodulated using direct detection. The chromatic dispersion of the other optical signal can then be adjusted to account for chromatic dispersion experienced by the other optical signal when it propagated through an optical fiber.