To reduce the size while being able to accurately monitor light of a plurality of wavelengths. An optical multiplexing circuit includes: a plurality of branching units each configured to divide light output from a corresponding one of a plurality of input waveguides; a multiplexing unit configured to multiplex beams each being one beam of the light divided by each of the plurality of branching units; an output waveguide configured to output the light multiplexed by the multiplexing unit; and a plurality of monitoring waveguides each configured to output another beam of the light divided by each of the plurality of branching units, wherein at least one monitoring waveguide of the plurality of monitoring waveguides includes a bent waveguide constituted by a rib-shaped waveguide.

A semiconductor photodetector comprising a closed loop configured to receive light from an external source adapted to trap light within said closed loop until absorption by the semiconductor.

An integrated optical polarizer for generating linear polarizing light may be formed in a photonic integrated circuit (PIC) for applications that require stable output state of polarization. The integrated polarizer may be built by using the same materials already present in the PIC without use of other additional layers and claddings, and without other additional structural modification to the waveguide profile. The integrated polarizer comprises a plurality of bending waveguides of a pre-determined radius that are connected to each other in sequence. The bending waveguide has a high birefringence and a loose confinement to conduct one polarization mode and attenuate the other polarization mode. The polarization discrimination is controlled with the degree of the mode confinement, the bending radius, and the number of the bending waveguides that are connected in series.

To reduce the size while being able to accurately monitor light of a plurality of wavelengths. An optical multiplexing circuit includes: a plurality of branching units each configured to divide light output from a corresponding one of a plurality of input waveguides; a multiplexing unit configured to multiplex beams each being one beam of the light divided by each of the plurality of branching units; an output waveguide configured to output the light multiplexed by the multiplexing unit; and a plurality of monitoring waveguides each configured to output another beam of the light divided by each of the plurality of branching units, wherein at least one monitoring waveguide of the plurality of monitoring waveguides includes a bent waveguide constituted by a rib-shaped waveguide.

An optical circuit for routing a signal includes a coupler and first and second waveguides. The coupler has an input for the signal and has first and second outputs. The first waveguide has a first optical connection to the first output, and the second waveguide has a second optical connection to the second output. Both waveguides have the same propagation length. The first and second waveguides include different widths at the respective optical connections to the respective outputs. This coupler can be used with another input couplers, two additional waveguides, and two 2×2 output couplers to provide a 90-degree hybrid for mixing signal light and local oscillator light in a coherent receiver or the like.

Embodiments of the disclosure provide a photonic integrated circuit (PIC) structure with a passage for a waveguide through a barrier structure. The PIC structure includes a barrier structure on a substrate, having a first sidewall and a second sidewall opposite the first sidewall. A passage is within the barrier structure, and extends from a first end at the first sidewall of the barrier structure to a second end at the second sidewall of the barrier structure. A shape of the passage includes a reversal segment between the first end and the second end. A waveguide within the passage and extends from the first end to the second end of the barrier structure.

An optical circuit for routing a signal includes a coupler and first and second waveguides. The coupler has an input for the signal and has first and second outputs. The first waveguide has a first optical connection to the first output, and the second waveguide has a second optical connection to the second output. Both waveguides have the same propagation length. The first and second waveguides include different widths at the respective optical connections to the respective outputs. This coupler can be used with another input couplers, two additional waveguides, and two 2×2 output couplers to provide a 90-degree hybrid for mixing signal light and local oscillator light in a coherent receiver or the like.

An optical semiconductor device includes a first optical coupler including a first input port and a second input port, a first optical branching device including a first output port and a second output port, a second optical coupler including a third input port and a fourth input port, a second optical branching device including a third output port and an fourth output port, a first single mode waveguide configured to connect the second input port and the first output port, a second single mode waveguide configured to connect the second output port and the third input port, a third single mode waveguide configured to connect the fourth input port and the third output port, and a fourth single mode waveguide configured to connect the fourth output port and the first input port.

An apparatus for an attenuation adjustment tool, the attenuation adjustment tool includes a body with an adjustment arm positioned at a first side of the body, where an actuator is configured to extend and retract the adjustment arm. The attenuation adjustment tool further includes an input port and an output port positioned at the first side of the body, wherein an input prong and an output prong of a wrap plug are each respectively insertable into the input port and the output port. The attenuation adjustment tool further includes the adjustment arm configurable to engage with a mechanism on the wrap plug, wherein the mechanism is configurable to alter a shape of a signal cable in the wrap plug.

According to an aspect of the present disclosure, an edge coupler for a photonic chip is provided. The edge coupler includes a substrate having a top surface, a sealed cavity in the substrate, a waveguide core, and a back-end-of-line stack. The sealed cavity has varying depths relative to the top surface of the substrate. The waveguide core is over the sealed cavity. The back-end-of-line stack includes a side edge, an interlayer dielectric layer, and an assisting waveguide. The assisting waveguide is on the interlayer dielectric layer adjacent to the side edge. The assisting waveguide and the waveguide core have an overlapping arrangement with the sealed cavity in the substrate.