An optical transmission module includes a photonic integrated circuit, a processor that controls the power state of the photonic integrated circuit, and a current source circuit that supplies electric current to a light source used for the photonic integrated circuit. The photonic integrated circuit has an optical multiplexer block including a plurality of multiplexers connected in a n-level tree structure (n is an integer greater than 1), 2{circumflex over ( )}n optical modulators connected to inputs of the optical multiplexer block, and a photodetector connected to an input or an output of each of the plurality of the multiplexers. The light source emits a light beam to be incident onto a corresponding one of the 2{circumflex over ( )}n optical multiplexers. The processor controls the current source circuit for each of the plurality of the multiplexers, based on the monitored value acquired from the photodetector provided to each of the plurality of the multiplexers.

A wavelength division multiplexing structure comprises a first wavelength division multiplexer and a second wavelength division multiplexer, each comprises N filtering units, a branch side interface connected to each filtering units, and a line side interface, N being a positive integer; each filtering unit corresponds to one central wavelength; the line side interface of the first wavelength division multiplexer and that of the second wavelength division multiplexer are connected by an optical fiber, the N filtering units are divided into multiple filtering unit groups, and the multiple filtering unit groups are cascaded in series or cascaded in a series-parallel combination; filter units in each filtering unit group are cascaded in series; and a cascade mode and/or cascade position corresponding to each filter unit in the first wavelength division multiplexer and the second wavelength division multiplexer is at least related to the center wavelengths corresponding to the filter unit.

Photonic devices, photonic integrated circuits, optical elements, and techniques of making and using the same are described. A photonic device includes an input region adapted to receive an optical signal including a multiplexed channel characterized by a distinct wavelength, a dispersive region optically coupled with the input region to receive the optical signal, the dispersive region including a plurality of sub-regions defined by an inhomogeneous arrangement of a first material and a second material, and a plurality of output regions optically coupled with the input region via the dispersive region. The plurality of sub-regions can include an input channel section, one or more coupler sections, and one or more branching sections. The plurality of sub-regions together can configure the photonic device to demultiplex the optical signal and to isolate the multiplexed channel at a first output region of the plurality of output regions.

Photonic devices, photonic integrated circuits, optical elements, and techniques of making and using the same are described. A photonic device includes an input region adapted to receive an optical signal including a multiplexed channel characterized by a distinct wavelength, a dispersive region optically coupled with the input region to receive the optical signal, the dispersive region including a plurality of sub-regions defined by an inhomogeneous arrangement of a first material and a second material, and a plurality of output regions optically coupled with the input region via the dispersive region. The plurality of sub-regions can include an input channel section, one or more coupler sections, and one or more branching sections. The plurality of sub-regions together can configure the photonic device to demultiplex the optical signal and to isolate the multiplexed channel at a first output region of the plurality of output regions.

A passive optical network includes a central office providing subscriber signals; a fiber distribution hub including an optical power splitter and a termination field; and a drop terminal. Distribution fibers have first ends coupled to output ports of a drop terminal and second ends coupled to the termination field. A remote unit of a DAS is retrofitted to the network by routing a second feeder cable from a base station to the hub and coupling one the distribution fibers to the second feeder cable. The remote unit is plugged into the corresponding drop terminal port, for example, with a cable arrangement having a sealed wave division multiplexer.

An optical amplifier includes: a pump-light source unit outputting pump light beams having respective phases modulated; a polarization multiplexer/demultiplexer having first, second, and third ports, demultiplexing a light beam, input from the first port, into polarization components and outputting the demultiplexed light components from the second port and the third port; a first polarization-sensitive optical amplifying fiber unit connected to the second port of the polarization multiplexer/demultiplexer; a second polarization-sensitive optical amplifying fiber unit connected to the third port of the polarization multiplexer/demultiplexer; optical multiplexers/demultiplexers connected to the first polarization-sensitive optical amplifying fiber unit and the second polarization-sensitive optical amplifying fiber unit, respectively; an optical discharge unit, connected between the first polarization-sensitive optical amplifying fiber unit and the second polarization-sensitive optical amplifying fiber unit, discharging the pump light beams to outside the optical loop; and an optical circulator, having first, second, and third ports, outputting a signal light beam.

A passive optical network includes a central office providing subscriber signals; a fiber distribution hub including an optical power splitter and a termination field; and a drop terminal. Distribution fibers have first ends coupled to output ports of a drop terminal and second ends coupled to the termination field. A remote unit of a DAS is retrofitted to the network by routing a second feeder cable from a base station to the hub and coupling one the distribution fibers to the second feeder cable. The remote unit is plugged into the corresponding drop terminal port, for example, with a cable arrangement having a sealed wave division multiplexer.

A wavelength-division multiplexing (WDM) optical assembly with increased lane density is disclosed herein. The WDM optical assembly includes a WDM optical core subassembly including an optical signal router for routing an optical signal between a first side and a second side of a substrate. The WDM optical core subassembly further includes a first WDM filter having a first passband and a second WDM filter having a second passband. The WDM optical core subassembly forms a first optical path between a first common port, the first WDM filter, and a first channel port, and to form a second optical path between the second WDM filter, a second common port, and a second channel port. The WDM optical core subassembly increases lane density while decreasing size and complexity by including a plurality of common ports in optical communication with the same plurality of WDM filters.

According to examples, an apparatus may include a wavelength division multiplexing (WDM) module including a WDM housing having a WDM front panel and a WDM component housed within the WDM housing. The apparatus may also include an optical time-domain reflectometer (OTDR)/switch module integrated with the WDM module, the OTDR/switch module including an OTDR housing having an OTDR front panel and an OTDR/switch component housed within the OTDR housing. The WDM housing may be connectable with the OTDR housing to cause respective side edges of the WDM front panel and the OTDR front panel to be adjacent to each other when the WDM housing is connected to the OTDR housing.

A wavelength division multiplexing structure comprises a first wavelength division multiplexer and a second wavelength division multiplexer, each comprises N filtering units, a branch side interface connected to each filtering units, and a line side interface, N being a positive integer; each filtering unit corresponds to one central wavelength; the line side interface of the first wavelength division multiplexer and that of the second wavelength division multiplexer are connected by an optical fiber; the N filtering units are divided into multiple filtering unit groups, and the multiple filtering unit groups are cascaded in series or cascaded in a series-parallel combination; filter units in each filtering unit group are cascaded in series; and a cascade mode and/or cascade position corresponding to each filter unit in the first wavelength division multiplexer and the second wavelength division multiplexer is at least related to the center wavelengths corresponding to the filter unit.