An optical fiber sensor includes a first single mode fiber, a second single mode fiber, and a multimode fiber positioned between, and coupled to, the first single mode fiber and the second single mode fiber. The multimode fiber includes a graded-index core with an outer diameter between about 35 m and about 45 m. A numerical aperture of the core is between about 0.15 and about 0.25. The multimode fiber includes a cladding with an outer diameter between about 70 m and about 90 m. A coupling strength of an LP.sub.01 mode of the first single mode fiber to each of an LP.sub.02 mode and an LP.sub.03 mode of the multimode fiber is at least about 0.25.

An optical interconnect device may include a multi-fiber connector at a first end of the optical interconnect device. The optical interconnect device may include an edge coupled connector at a second end of the optical interconnect device. The optical interconnect device may include a plurality of optical fibers disposed inside the multi-fiber connector and the edge coupled connector to optically couple the multi-fiber connector to the edge coupled connector, wherein the multi-fiber connector and the edge coupled connector rigidly interconnect to structurally support the optical interconnect device.

Embodiments disclosed herein generally relate to optical coupling between a highly-confined waveguide region and a low confined waveguide region in an optical device. The low confined waveguide region includes a trench in a substrate of the optical device in order to provide additional dielectric layer thickness for insulation between the substrate of the optical device and waveguides for light signals having a low optical mode. The low confined waveguide region is coupled to the highly-confined waveguide region via a waveguide overlap and in some embodiments via an intermediary coupling waveguide.

An integrated mode converter and multiplexer (/demultiplexer) is disclosed, which combines a multimode interference coupler (100), at least one phase-shifter (200) and a symmetrical Y-junction (300). The dispersion of the multimode interference coupler (100) is engineered through subwavelength structures in order to achieve a very wide bandwidth. Several phase-shifter (200) topologies for further bandwidth enhancement are disclosed, as well as architectures for multiplexing a greater number of optical modes.

A class of fibers is described that have a non-circular cross section on one or both ends that can by optimized to capture the optical radiation from a laser diode or diode array and deliver the light in the same or different shape on the opposite end of the fiber. A large multimode rectangular waveguide may be provided which can accept the radiation from a high-power diode bar and transform it into a circular cross section on the opposite end, while preserving brightness.

Under one aspect, a method for performing an operation is provided. The method can include receiving, by different physical locations of a multi-mode waveguide, an input signal and a plurality of coefficients imposed on laser light. The method also can include generating, by the multi-mode waveguide, a speckle pattern based on the different physical locations, the input signal, and the plurality of coefficients. The method also can include adjusting at least one of the coefficients based on the speckle pattern.

Under one aspect, a method for performing an operation is provided. The method can include receiving, by different physical locations of a multi-mode waveguide, an input signal and a plurality of coefficients imposed on laser light. The method also can include generating, by the multi-mode waveguide, a speckle pattern based on the different physical locations, the input signal, and the plurality of coefficients. The method also can include adjusting at least one of the coefficients based on the speckle pattern.

An optical demultiplexer/multiplexer, comprising: a multimode interference waveguide; at least one first coupling waveguide which meets the multimode interference waveguide at least one first location and a plurality of second coupling waveguides which meet the multimode interference waveguide at a plurality of second locations which are spaced in a direction of transmission in relation to the at least one first location, with the at least one first coupling waveguide and the second coupling waveguides together with the multimode interference waveguide providing a first angled multimode interferometer which operates to demultiplex a first optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a first optical signal having optical channels of the plurality of wavelengths; at least one third coupling waveguide which meets the multimode interference waveguide at least one third location and a plurality of fourth coupling waveguides which meet the multimode interference waveguide at a plurality of fourth locations which are spaced in a direction of transmission in relation to the at least one third location, with the at least one third coupling waveguide and the plurality of fourth coupling waveguides together with the multimode interference waveguide providing a second angled multimode interferometer which operates to demultiplex a second optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a second optical signal having optical channels of the plurality of wavelengths; whereby the demultiplexer/multiplexer provides for the demultiplexing/multiplexing of first and second optical signals having optical channels of a plurality of wavelengths. In a further embodiment the first coupling waveguide of an optical demultiplexer/multiplexer comprising a first angled multimode interferometer is stepped or tapered in order to couple a signal having a broadened spatial, or spectral, profile. In another embodiment of an optical demultiplexer/multiplexer comprising a first angled multimode interferometer a plurality of first coupling waveguides are coupled to a photonic structure which provides a plurality of output signals having substantially equal intensity and a phase difference, also in order to couple a signal or signals having a broadened spatial, or spectral, profile. In yet another embodiment of an optical demultiplexer/multiplexer comprising a first angled multimode interferometer the multimode interference waveguide includes a reflector at one end.

An optical system includes a silicon (Si) substrate, a buried oxide (BOX) layer formed on the substrate, a silicon nitride (SiN) layer formed above the BOX layer, and a SiN waveguide formed in the SiN layer. In some embodiments, the optical system may additionally include an interposer waveguide adiabatically coupled to the SiN waveguide to form a SiN-interposer adiabatic coupler that includes at least the tapered section of the SiN waveguide, the optical system further including at least one of: a cavity formed in the Si substrate at least beneath the SiN-interposer adiabatic coupler or an oxide overlay formed between a top of a SiN core of the SiN waveguide and a bottom of the interposer waveguide. Alternatively or additionally, the optical system may additionally include a multimode SiSiN adiabatic coupler that includes a SiN taper of a SiN waveguide and a Si taper of a Si waveguide.

An optical fiber sensor includes a first single mode fiber, a second single mode fiber, and a multimode fiber positioned between, and coupled to, the first single mode fiber and the second single mode fiber. The multimode fiber includes a graded-index core with an outer diameter between about 35 m and about 45 m. A numerical aperture of the core is between about 0.15 and about 0.25. The multimode fiber includes a cladding with an outer diameter between about 70 m and about 90 m. A coupling strength of an LP.sub.01 mode of the first single mode fiber to each of an LP.sub.02 mode and an LP.sub.03 mode of the multimode fiber is at least about 0.25.