An MCF of the present embodiment has eight or more cores. A diameter of a common cladding is not more than 126 m. Optical characteristics of each core are as follows: a TL at a predetermined wavelength of 1310 nm is not more than 0.4 dB/km; an MFD at the predetermined wavelength is from 8.0 m to 10.1 m; a BL in a BR of not less than 5 mm or in the BR of not less than 3 mm and, less than 5 mm is not more than 0.25 dB/turn at the predetermined wavelength; 0 is from 1300 nm to 1324 nm; cc is not more than 1260 nm; an XT or XTs at the predetermined wavelength is not more than 0.001/km.

A silicon photonic device comprises a silicon core having a core refractive index and a structure formed in the silicon core. The structure comprises a first refractive index variation pattern across the core in a first direction (x) and having a first modulation depth (H.sub.1), and a second refractive index variation pattern across the core in a second, orthogonal, direction (y) and having a second modulation depth (H.sub.2), less than the first modulation depth. The first refractive index variation pattern overlays the second refractive index variation pattern, forming a three-dimensional structure. The first refractive index variation pattern only supports propagation of light having a TM mode between the first direction and a third direction (z) and the second refractive index variation pattern only supports propagation of light having a TE mode between the second direction and the third direction.

A silicon photonic device (1) comprising: a silicon core (2) having a core refractive index; and a structure formed in the silicon core, comprising: a first refractive index variation pattern (4) across the core in a first direction (x) and having a first modulation depth (H.sub.i); and a second refractive index variation pattern (6) across the core in a second, orthogonal, direction (y) and having a second modulation depth (H.sub.2), less than the first modulation depth. The first refractive index variation pattern overlays the second refractive index variation pattern, forming a three-dimensional structure. The first refractive index variation pattern only supports propagation of light having a TM mode between the first direction and a third direction (z) and the second refractive index variation pattern only supports propagation of light having a TE mode between the second direction and the third direction. An optical waveguide coupler is also disclosed. The optical waveguide coupler comprises a plurality of planar waveguides, each supporting propagation of one of a TE and a TM mode, and a plurality of silicon diffractive gratings each comprising a planar silicon core and a grating structure formed by a periodic refractive index variation extending across the core in a first direction and having a grating period and a modulation depth, these selected to cause the grating to support propagation of the light between the first direction and a third direction substantially orthogonal to the planar silicon core. Additionally the optical waveguide coupler comprises a plurality of tapered planar waveguides.

An MCF of the present embodiment has eight or more cores. A diameter of a common cladding is not more than 126 m. Optical characteristics of each core are as follows: a TL at a predetermined wavelength of 1310 nm is not more than 0.4 dB/km; an MFD at the predetermined wavelength is from 8.0 m to 10.1 m; a BL in a BR of not less than 5 mm or in the BR of not less than 3 mm and, less than 5 mm is not more than 0.25 dB/turn at the predetermined wavelength; 0 is from 1300 nm to 1324 nm; cc is not more than 1260 nm; an XT or XTs at the predetermined wavelength is not more than 0.001/km.

An MCF of the present embodiment has eight or more cores. A diameter of a common cladding is not more than 126 m. Optical characteristics of each core are as follows: a TL at a predetermined wavelength of 1310 nm is not more than 0.4 dB/km; an MFD at the predetermined wavelength is from 8.0 m to 10.1 m; a BL in a BR of not less than 5 mm or in the BR of not less than 3 mm and, less than 5 mm is not more than 0.25 dB/turn at the predetermined wavelength; 0 is from 1300 nm to 1324 nm; cc is not more than 1260 nm; an XT or XTs at the predetermined wavelength is not more than 0.001/km.

A silicon photonic device (1) comprising: a silicon core (2) having a core refractive index; and a structure formed in the silicon core, comprising: a first refractive index variation pattern (4) across the core in a first direction (x) and having a first modulation depth (H.sub.i); and a second refractive index variation pattern (6) across the core in a second, orthogonal, direction (y) and having a second modulation depth (H.sub.2), less than the first modulation depth. The first refractive index variation pattern overlays the second refractive index variation pattern, forming a three-dimensional structure. The first refractive index variation pattern only supports propagation of light having a TM mode between the first direction and a third direction (z) and the second refractive index variation pattern only supports propagation of light having a TE mode between the second direction and the third direction. An optical waveguide coupler is also disclosed. The optical waveguide coupler comprises a plurality of planar waveguides, each supporting propagation of one of a TE and a TM mode, and a plurality of silicon diffractive gratings each comprising a planar silicon core and a grating structure formed by a periodic refractive index variation extending across the core in a first direction and having a grating period and a modulation depth, these selected to cause the grating to support propagation of the light between the first direction and a third direction substantially orthogonal to the planar silicon core. Additionally the optical waveguide coupler comprises a plurality of tapered planar waveguides.

Disclosed is an optical fiber pressure sensor including: a polarization beam splitter that splits input light from a broadband light source into two beams; a polarization controller through which vertically and horizontally polarized light coming out of the polarization beam splitter pass; a pressure chamber in which the polarization beam splitter and the polarization controller may be placed; and an optical spectrum analyzer into which vertically and horizontally polarized light passing through the polarization controller and getting out of the polarization beam splitter is introduced, wherein the pressure chamber includes a polarization-maintaining fiber and an optical fiber Bragg grating.

In an optical fiber comprising a central axis (z) with a cladding that extend along z and a coating that is disposed about the cladding, a twist with a twist period () is imparted on the optical fiber about z. The twist mitigates micro-bend-induced cross-talk. The cladding comprises a substantially circular axial cross section. The substantially circular axial cross-section comprises a cladding center and a cladding outer diameter (ODclad). Multiple cores (e.g., a first core, a second core, etc.) are disposed within the cladding. At least one core is disposed helically about z to form a helical core, with the helical core comprising a helical pitch (p) that is approximately equal to (meaning, p). The twist has a twist period () that is less than 9.1 centimeters (meaning, <9.1 cm).

A multicore optical fiber includes a plurality of cores along a fiber axis and cladding surrounding the plurality of cores. The plurality of cores includes a first core having an elliptical shape in a cross section orthogonal to the fiber axis and one or more second cores different from the first core. The non-circularity of the elliptical shape is 0.1% or more. In the cross section orthogonal to the fiber axis, an angle formed by a straight line connecting a center of gravity of the first core and a center of gravity of a core group including one or more second cores and a straight line along a major axis of the elliptical shape is 30 degrees or less. Polarization mode dispersion is 0.2 ps/rtkm or less.

A polarization-maintaining dispersion-compensation microstructure fiber includes an inner core, an air-hole array in area 1 and an air-hole array in area 2. The air holes in the area 1 and 2 air-hole arrays are arranged in square lattice. The air-hole arrays in areas 1 and 2 are dislocated by half-layer along y-direction. In area 1, 2 air holes in the middle row are omitted to form a solid area as the inner core. 2 outer cores are located in 2 sub-areas of area 2, and each outer core contains 2 air holes. The long (or short) axes of the inner and outer cores are perpendicular, and the center points of the inner core and the two outer cores are located on the x-axis.