Multicore optical fibers with low bend loss, low cross-talk, and large mode field diameters In some embodiments a circular multicore optical fiber includes a glass matrix; at least 3 cores arranged within the glass matrix, wherein any two cores have a core center to core center spacing of less than 29 microns; and a plurality of trench layers positioned between a corresponding core and the glass matrix, each trench layer having an outer radius of less than or equal to 14 microns and a trench volume of greater than 50% Δ micron.sup.2; wherein the optical fiber has a mode field diameter of greater than about 8.2 microns at 1310 nm, and wherein the optical fiber has an outer diameter of less than about 130 microns.

The present disclosure provides optical fibers with an impact-resistant coating system. The fibers feature low microbending and high mechanical reliability. The coating system includes a primary coating and a secondary coating. The primary coating and secondary coating have reduced thickness to provide reduced radius fibers without sacrificing protection. The primary coating has a low spring constant and sufficient thickness to resist transmission of force to the glass fiber. The secondary coating has high puncture resistance. The outer diameter of the optical fiber is less than or equal to 200 μm.

A disclosed multimode optical fiber comprises a core and a cladding surrounding the core. The core has an outer radius r.sub.1 in between 20 μm and 30 μm. The cladding includes a first outer cladding region having an outer radius r.sub.4a and a second outer cladding region having an outer radius r.sub.4b less than or equal to 45 μm. The second outer cladding region comprises silica-based glass doped with titania. The optical fiber further includes a primary coating with an outer radius r.sub.5 less than or equal to 80 μm, and a thickness (r.sub.5−r.sub.4) less than or equal to 30 μm. The optical fiber further includes a secondary coating with an outer radius r.sub.6 less than or equal to 100 μm. The secondary coating has a thickness (r.sub.6−r.sub.5) less than or equal to 30 μm, and a normalized puncture load greater than 3.6×10.sup.−3 g/micron.sup.2.

An optical fiber includes a glass portion, a primary coating layer, and a secondary coating layer. In the optical fiber, a value of microbend loss characteristic factor F.sub.μBL_GO is 2.6 ([GPa.sup.−1.Math.μm.sup.−10.5.Math.dB/turn].Math.10.sup.−27) or less, when represented by

F.sub.μBL_GO=F.sub.μBL_G×F.sub.μBL_O

by using geometry microbend loss characteristic F.sub.μBL_G and optical microbend loss characteristic F.sub.μBL_O.

The invention concerns a method for characterizing mode group properties of multimodal light traveling through an optical component, comprising: launching a reference pulse of light with a wavelength λ.sub.t from a light source into said optical component, collecting light signal output by said optical component into a Mode Group Separating optical fiber; detecting light signal output by said Mode Group Separating optical fiber. The Mode Group Separating optical fiber is a multimode fiber with an α-profile graded index core with an α-value chosen such that said fiber satisfies the following criterion at the wavelength λ.sub.t: $\frac{.Math.\mathrm{\Delta \tau }.Math..L}{\Delta T_{\mathrm{REF}}}>4$
where: Δτ is a time delay difference between consecutive mode groups; L is a length of said fiber; ΔT.sub.REF is a Full Width at Quarter Maximum of said reference pulse.

Methods and apparatuses for quantitatively measuring strain in an optical fiber. An optical source comprising an optical beam generator and a pulse generator receives instructions from a controller and generates a pulsed optical beam in response to those instructions. The pulsed optical beam is directed into an optical fiber to generate a reflected beam from scattering centers within the optical fiber. A detector records a plurality of frames of data generated by the reflected beam, and the controller tracks an evolution of a speckle pattern carried by the reflected beam from the plurality of frames and calculates a strain induced in a section of the optical fiber from the evolution of the speckle pattern.

A method of categorizing single mode optical fibers, the method including determining one or more fiber properties of an optical fiber, the optical fiber being a single mode optical fiber at an operating wavelength of about 1310 nm. The method further including calculating a peak bandwidth wavelength of the optical fiber based on the one or more fiber properties, comparing the calculated peak bandwidth wavelength with a target peak bandwidth wavelength and based on the comparison, determining if the optical fiber meets a target modal bandwidth.

Disclosed herein are configurations for few-mode fiber optical endoscope systems employing distal optics and few-mode, double-clad or other optical fiber wherein the systems directing an optical beam to a sample via the optical fiber; collecting light backscattered from the sample; direct the backscattered light to a detector via the optical fiber; and detect the backscattered light; wherein the directed optical beam is single mode and the collected light is one or more higher order modes.

The present disclosure relates to a multi-core optical fiber including:

M (where M is a positive integer of 1 or larger) group(s) each consisting of N (where N is a positive integer of 2 or larger) core regions linearly arranged in a cross section; a cladding region that surrounds the plurality of core regions and has a refractive index lower than any of the plurality of core regions; and a coating region that surrounds the cladding region, wherein the plurality of core regions are arranged in line symmetry with respect to both imaginary lines orthogonal to each other at a center of the cladding region, a diameter of the cladding region is 180 μm or less, and a diameter of the coating region is 235 μm or more and 265 μm or less.

An optical device may include a fiber to provide a beam. The optical device may include a graded-index element to expand or magnify the beam. An input facet of the graded-index element may be adhered to an output facet of the fiber. The optical device may include an optical transformation element to transform the beam after the beam is expanded or magnified by the graded-index element. An input facet of the optical transformation element may be adhered to an output facet of the graded-index element. The optical transformation element may comprise at least one active optical element or may be non-birefringent such that orthogonal polarizations of the beam do not experience distinct phase transformations.