A polarization rotator and a polarization stabilizer. The polarization rotator includes a rib waveguide. The rib waveguide including: a slab portion; and a ridge portion, which is disposed along a surface of the slab portion. The slab portion has a first slab region whose width, as measured in a direction perpendicular to a guiding direction of the waveguide, increases from a first slab width to a second slab width along a first length, and the ridge portion has a first ridge region whose width, as measured in the same direction as the slab widths, decreases from a first ridge width to a second ridge width along the same first length; such that the rotator is configured to rotate the polarization of light during its transmission through the rib waveguide.

A two-fiber Quad Small Form-factor Pluggable electro-optical transceiver (QSFP) currently connects to two optical fibers, one for transmission and one for reception. In accordance with an embodiment of the disclosure, a three-port optical circulator may be employed in order to achieve bidirectional transmission (BiDi) on a single fiber. The disclosure provides in accordance with an embodiment of the disclosure a miniature optical circulator that clips onto the two-fiber QSFP without protruding from the QSFP extraction lever, and is configured to mate with the two QSFP fiber connectors on one side and a single optical fiber on the other. Another embodiment provides an integrated bidirectional QSFP that is configured to mate with a single bidirectional fiber.

Examples herein relate to polarization diversity optical interface assemblies including a single mode optical fiber and first and second grating couplers disposed on a substrate. The first and second grating couplers are coupled to first and second waveguides, respectively. The assemblies further includes an optical connector to couple light between the single mode optical fiber and each of the first and second grating couplers. The optical connector includes a ferrule and a walk-off crystal. The ferrule is coupled to a portion of the single mode optical fiber. The walk-off crystal is configured to spatially separate the light into first and second orthogonal polarization modes prior to passing through the respective first and second grating couplers and/or combine the first and second polarization modes of the light prior to passing through the single mode optical fiber.

Examples herein relate to polarization diversity optical interface assemblies including a single mode optical fiber and first and second grating couplers disposed on a substrate. The first and second grating couplers are coupled to first and second waveguides, respectively. The assemblies further includes an optical connector to couple light between the single mode optical fiber and each of the first and second grating couplers. The optical connector includes a ferrule and a walk-off crystal. The ferrule is coupled to a portion of the single mode optical fiber. The walk-off crystal is configured to spatially separate the light into first and second orthogonal polarization modes prior to passing through the respective first and second grating couplers and/or combine the first and second polarization modes of the light prior to passing through the single mode optical fiber.

A polarization rotator and a polarization stabilizer. The polarization rotator includes a rib waveguide. The rib waveguide including: a slab portion; and a ridge portion, which is disposed along a surface of the slab portion. The slab portion has a first slab region whose width, as measured in a direction perpendicular to a guiding direction of the waveguide, increases from a first slab width to a second slab width along a first length, and the ridge portion has a first ridge region whose width, as measured in the same direction as the slab widths, decreases from a first ridge width to a second ridge width along the same first length; such that the rotator is configured to rotate the polarization of light during its transmission through the rib waveguide.

A polarization rotator structure includes: a first core structure formed at a first layer, extending from the first end to a second end, and a second core structure formed at a second layer that is at a different depth than the first layer and formed in proximity to the first core structure. The first core structure and the second core structure provide mode hybridization between at least two orthogonally polarized waveguide modes of the PRS. An optical splitter structure is optically coupled at a first end to the second end of the PRS, and optically coupled at a second end to at least two optical waveguides, and includes: a first core structure that is contiguous with at least one of the first or second core structures of the PRS, and a second core structure that is separate from both of the first and second core structures of the PRS.

A bidirectional optical transmission apparatus includes a first optical waveguide device, a second optical waveguide device, and a polarization-maintaining optical fiber that connects the first optical waveguide device and the second optical waveguide device. A direction of a slow axis of the polarization-maintaining optical fiber with respect to a first substrate at a connecting portion between the first optical waveguide device and the polarization-maintaining optical fiber and a direction of the slow axis of the polarization-maintaining optical fiber with respect to the second substrate at a connecting portion between the second optical waveguide device and the polarization-maintaining optical fiber are substantially orthogonal to each other.

An optical waveguide (100) is disclosed, for guiding light in a photonic circuit comprising a layer of phase change material (101) for modulating the phase of the guided light. The phase change material (101) is switchable between at least a stable crystalline state and a stable amorphous state each with different refractive indexes. The phase change material (101) exhibits an extinction coefficient of less than 0.1 in both states for wavelengths greater than 1000 nm.

A bricked sub-wavelength periodic waveguide and a modal adapter, power divider and polarization splitter that use the waveguide. The waveguide includes blocks disposed periodically with a period L.sub.z on a substrate and which alternate with a covering material. The first blocks have a width a.sub.x and the second blocks have a width b.sub.x, alternating on the substrate according to a period L.sub.x the second blocks being shifted a distance d.sub.z the first blocks in the direction of propagation. A modal adapter, a power divider and a polarization splitter all use the periodic waveguide and can operate with larger wave periods without leaving the sub-wavelength regime.