An optical fiber sensor extends coaxially with a controllable heater to provide high-resolution axial measurement of thermal properties such as thermal convection of the surrounding, Heat removal by either conduction or convection may be used to deduce material height in a tank, or velocity of flow when coupled with localized heating, or other aspects of the material based on thermal conductivity.

A single-ended output circulator includes a three-core optical fiber head having first, second, and third optical fiber cores; a walk-off crystal having a first surface facing towards the second end of the three-core optical fiber head tube and a second surface facing away from the second end of the three-core optical fiber head tube; a plurality of half-wave plates each having a first surface coupled to the second surface of the walk-off crystal and a second surface facing away from the second surface of the walk-off crystal; a collimating lens having a first end and a second end; a reflection mirror configured to reflect light beams from the collimating lens; an optical prism between the collimating lens and the reflection mirror and configured to transmit a light beam along a propagation direction according to a polarization direction of the light beam; and a polarization rotator.

To provide an optical communication system and an optical communication method able to achieve a high reliable access network capable of long haul distance transmission considering the optical energy efficiency even if the user distribution is biased. An uneven branch optical splitter included in an optical communication system according to the present invention can output the optical intensities different for each output port by adjusting the branching configuration and the branching ratio. For example, a reach transmission distance of the farmost user can be extended or the number of connectible users can be increased by adjusting the branching configuration of the uneven branch optical splitter or the branching ratios such that the near minimum reception sensitivity is given for the ONU installed near the telecommunications carrier.

Methods and systems for eliminating polarization dependence for 45 degree incidence MUX/DEMUX designs may include an optical transceiver, where the optical transceiver comprises an input optical fiber, a beam splitter, and a plurality of thin film filters arranged above corresponding grating couplers in a photonics die. The transceiver may receive an input optical signal comprising different wavelength signals via the input optical fiber, split the input optical signal into signals of first and polarizations using the beam splitter by separating the signals of the second polarization laterally from the signals of the first polarization, communicate the signals of the first polarization and the second polarization to the plurality of thin film filters, and reflect signals of each of the plurality of different wavelength signals to corresponding grating couplers in the photonics die using the thin film filters.

The present disclosure is directed to photonic wavelength division multiplexing (WDM) receivers with polarization diversity and/or low reflectance. In embodiments, a WDM receiver is provided with a splitter, a plurality of waveguides and a plurality of photodetectors in series. The waveguides having particular equal path lengths relationship from the splitter to respective ones of the photodetectors. In other embodiments, the WDM receiver is provided with a splitter, a looped waveguide, a plurality of photodetectors, and a plurality of variable optical attenuators (VOAs). The VOAs are configured to suppress reflection of signal beams back to the transmitter. In various embodiments, the WDM receiver is a receiver sub-assembly of a silicon photonic transceiver disposed in a silicon package. Other embodiments may be described and/or claimed.

Structures for a polarization splitter and methods of fabricating a structure for a polarization splitter. First and second waveguide cores of the polarization splitter are located adjacent to each other in a coupling region. A third waveguide core is located over the second waveguide core in the coupling region. The third waveguide core is composed of a material having a variable refractive index.

An optical coupling apparatus includes: a coupling and polarization beamsplitter, a phase shifter, a 22 adjustable beamsplitter, a photoelectric detector, and a microprocessor. Light in any polarization direction can be coupled from an optical fiber into a waveguide, an extra insertion loss is small, intrinsic insertion losses for light in different polarization directions are the same, a structure is simple, and miniaturization is easy to be implemented.

An optical multiplexer includes a polarizer, a receptacle, a rotator disposed between the polarizer and the receptacle to rotate polarization planes of a pair of linearly polarized light beams in a forward direction and a polarization plane of a light beam in an opposite direction by 45 degrees, the forward direction being from the polarizer toward the receptacle, the opposite direction being from the receptacle to the polarizer, and a birefringent prism disposed between the rotator and the receptacle to multiplex the pair of linearly polarized light beams in the forward direction and to split the light beam in the opposite direction into an ordinary ray and an extraordinary ray. The rotator and the birefringent prism are fixed to the receptacle.

Methods and systems for CWDM MUX/DEMUX designs for silicon photonics interposers are disclosed and may include an optical transceiver including a silicon photonics interposer, a polarization splitter, a lens array, and a prism with a coarse wavelength division multiplexing (CWDM) coating and a high reflectivity (HR) coating. The polarization splitter, lens array, and prism are coupled to the silicon photonics interposer. An input optical signal of a plurality of different wavelengths and polarizations may be received. Signals of different polarization may be spatially separated using the polarization splitter and signals of a first wavelength range may be reflected into the lens array using the CWDM coating while signals in a second wavelength range may be passed through. Signals of the second wavelength range may be reflected to the lens array using the HR coating, and optical signals may be coupled into the silicon photonics interposer using the lens array.

The present disclosure relates to a waveplate having a substrate forming an optic. The substrate may have an integral portion forming a plurality of angled columnar features on an exposed surface thereof. The plurality of angled columnar features may further be aligned parallel with a directional plane formed non-parallel to a reference plane, with the reference plane being normal to a surface of the substrate. The metasurface forms a birefringent metasurface.