An optical fiber sensor includes an optical fiber. The optical fiber includes a cladding having a cladding refractive index, and a plurality of fiber cores embedded in the cladding and extending along a longitudinal axis of the optical fiber. The plurality of fiber cores include a first subset of at least one first fiber core and a second subset of at least one second fiber core. The at least one first fiber core has a first core refractive index different from the cladding refractive index and a first core radius in a direction transverse to the longitudinal axis. The at least one second fiber core has a second core refractive index different from the cladding refractive index and a second core radius transverse to the longitudinal axis. The second core refractive index and the second core radius differ from the first core refractive index and the first core radius such that a temperature sensitivity of the at least one second fiber core differs from the temperature sensitivity of the first fiber core.

A multi-core fiber includes: a plurality of cores; and a cladding portion formed around outer peripheries of the cores. Further, the cores each have a propagation characteristic conforming to any one of a plurality of standards for optical propagation characteristics, and of the cores, cores that are closest to each other conform to standards different from each other.

A fiber includes M primary cores and N redundant cores, where M an integer is greater than two and N is an integer greater than one. Interferometric circuitry detects interferometric pattern data associated with the M primary cores and the N redundant cores when the optical fiber is placed into a sensing position. Data processing circuitry calculates a primary core fiber bend value for the M primary cores and a redundant core fiber bend value for the N redundant cores based on a predetermined geometry of the M primary cores and the N redundant cores in the fiber and detected interferometric pattern data associated with the M primary cores and the N redundant cores. The primary core fiber bend value and the redundant core fiber bend value are compared in a comparison. The detected data for the M primary cores is determined reliable or unreliable based on the comparison. A signal is generated in response to an unreliable determination.

A hybrid sensing-communication system includes a multicore optical fiber that includes first and second cores, a first communication device optically coupled to a first end of the first core of the multicore optical fiber, a second communication device optically coupled to a second end of the first core of the multicore optical fiber, a first sensing device optically coupled to a first end of the second core of the multicore optical fiber, and a second sensing device optically coupled to a second end of the second core of the multicore optical fiber. The first and second communication devices exclusively exchange communication data along the first core, the first and second sensing devices exclusively exchange sensing data along the second core, and the communication data is different from the sensing data.

An MCF having a structure excellent in mass productivity and suppressing increases in splicing cost and loss are provided. The MCF includes 12 or 16 cores, a cladding, and a coating. The cores are arranged at positions of line symmetry while no adjacent relationship is established between the cores having an adjacent relationship with any core. A coating diameter is 235-265 .Math.m, a cladding diameter CD is from CD.sub.nominal -1 .Math.m to CD.sub.nominal +1 .Math.m with a nominal value CD.sub.nominal of 195 .Math.m or less, an MFD at 1310 nm is from MFD-reference-value -0.4 .Math.m to the MCF-reference-value+0.4 .Math.m with the MFD-reference-value of 8.2-9.2 .Math.m, and a 22m-cable-cutoff wavelength λ.sub.cc is 1260-1360 nm. A core’s zero-dispersion wavelength is a wavelength-reference-value - 12 nm to the wavelength-reference-value+12 nm with the wavelength-reference-value of 1312-1340 nm, and a dispersion slope at the wavelength is 0.092 ps/(nm.sup.2.Math.km) or less. A shortest distance from a cover-cladding interface to each core center, a structure, and optical characteristics satisfy predetermined conditions.

Embodiments of the present disclosure provide example multi-core fiber interleavers, example optical fiber amplifiers, example transmission systems, and example transmission methods. One example multi-core fiber interleaver includes a first port, a second port, a third port, and a fourth port, respectively adapted to be coupled to a first multi-core fiber, a second multi-core fiber, a third multi-core fiber, and a fourth multi-core fiber. A first subset of a plurality of first cores is coupled to a first subset of a plurality of second cores. A first subset of a plurality of third cores is coupled to a first subset of a plurality of fourth cores. A second subset of the plurality of fourth cores is coupled to a second subset of the plurality of second cores. A second subset of the third cores is coupled to a second subset of the first cores.

A system for producing a multicore optical fiber includes a source of electromagnetic radiation in a spectral range that is suitable for inducing photopolymerization of a transparent polymer. An arrangement of one or more optical components is configured to concurrently focus the radiation that is emitted by the source on a plurality of elongated regions of the transparent polymer so as to photopolymerize the transparent polymer solely in the elongated regions to increase the index of refraction of the elongated regions such that in the optical fiber that is formed of the transparent polymer after the elongated regions are photopolymerized, each of the elongated regions functions as a core of the optical fiber and regions of the transparent polymer that surround the elongated regions function as a cladding of each of the cores.

The invention relates to an optical waveguide with two or more light-guiding cores (1a-1e) extending continuously along the longitudinal extension of the optical waveguide, parallel to one another and spaced apart from one another, from one end of the optical waveguide to the other, and with a first cladding (2) enclosing the cores (1a-1e). It is an object of the invention to provide a multicore optical waveguide for high-power operation with reduced system complexity compared to the prior art. This object is achieved by the invention in that the cores (1a-1e) are arranged relative to one another and are spaced apart from one another in such a way that the propagation modes of the light propagating in the optical waveguide at a working wavelength couple to one another, the length of the optical waveguide being selected such that the light coupled into only a single one of the cores (1a-1e) at one end of the optical waveguide first spreads to the other cores (1a-1e) during propagation through the optical waveguide and, after passing through the optical waveguide, leaves the optical waveguide again at the other end from a single core (1a) with at least 60%, preferably at least 75%, of the total light power propagating in the optical waveguide. The invention also relates to a laser system with such an optical waveguide as an optical amplifier, and a method for guiding light in an optical waveguide.

A low-crosstalk large-capacity few-mode optical fiber includes an optical fiber cladding. Few-mode units are arranged in the optical fiber cladding, each few-mode unit sequentially includes a few-mode fiber core, an inner cladding and a trench from inside to outside, and a high-refractive-index ring is arranged in the few-mode fiber core. The few-mode units include first few-mode subunits, second few-mode subunits and third few-mode subunits, where the first few-mode subunits, the second few-mode subunits and the third few-mode subunits are arranged at intervals. The first few-mode subunit includes a first few-mode fiber core, the second few-mode subunit includes a second few-mode fiber core, and the third few-mode subunit includes a third few-mode fiber core, the radii and refractive indexes of the first few-mode fiber cores, the second few-mode fiber cores and the third few-mode fiber cores being different, respectively.

A method of fabricating an optical fiber, the method including providing a core portion including a doped portion having greater than or equal to 1.6 wt. % of a halide dopant and eliminating seed precursor sites at an exterior surface of the core portion, the seed precursor sites forming seeds in the optical fiber, wherein the eliminating the seed precursor sites includes one or more of: (i) fabricating the core portion by densifying an exterior portion of a silica soot body prior to exposing the silica soot body to the halide dopant, and (ii) exposing the exterior surface of the core portion to a reactive etchant. The method further including forming an optical fiber preform by applying cladding material to the exterior surface of the core portion and drawing the fiber preform into the optical fiber.