An optical fiber includes: a core; a depressed layer surrounding the core; and a cladding surrounding the depressed layer. A refractive index profile of the core is an α-th power distribution having an index α of 1.0 or more and 2.9 or less. A relative refractive index difference Δ.sup.− of the depressed layer with respect to the cladding has an absolute value |Δ.sup.−| that is 0.05% or more and 0.15% or less. A ratio r1/r2 of a radius r1 of the core to an outer radius r2 of the depressed layer is 0.35 or more and 0.60 or less. A cable cutoff wavelength λcc of 22 m is less than 1.26 μm. A mode field diameter at a wavelength of 1.31 inn is larger than 8.6 inn and smaller than 9.5 μm.

An optical fiber includes a glass fiber and a coating resin covering an outer periphery of the glass fiber. The glass fiber includes a core and a cladding. An outer diameter of the glass fiber is 99 μm or larger and 101 μm or smaller. The coating resin includes a cured material of an ultraviolet curing resin composition. An outer diameter of the coating resin is 160 μm or larger and 170 μm or smaller. A mode field diameter for light having a wavelength of 1310 nm is 7.2 μm or larger and 8.2 μm or smaller. Bending loss at a wavelength of 1550 nm when wound in a ring shape having a radius of 10 mm is 0.1 dB/turn or less. Bending loss at the wavelength of 1550 nm when wound in the ring shape having the radius of 7.5 mm is 0.5 dB/turn or less.

At least one embodiment relates to an apparatus for super-resolution fluorescence-microscopy imaging of a sample. The apparatus includes an objective lens having a forward field of view, the objective lens being configured to collect light. The apparatus may also include a processing arrangement configured to perform super-resolution fluorescence-microscopy imaging of the sample with the collected light. Further, the apparatus includes a waveguide component located forward of the objective lens and configured to (i) receive light from outside the forward field of view, and (ii) use total internal reflection within the waveguide component to direct excitation light. In addition, the apparatus includes an electronic optical-path control system configured to cause input light of a first wavelength to follow a first optical path corresponding to a first optical mode and also configured to cause input light of the first wavelength to follow a second optical path corresponding to a second optical mode.

A fiber includes a core and cladding, both of which may have temperature dependent indices of refraction. The materials and size of the core and cladding may be selected such that as the temperature of the core and/or cladding is heated above room temperature, the fiber transitions from supporting multimode optical waveguiding to supporting single mode waveguiding.

A gain fiber assembly for use in optical fiber amplification systems such as fiber amplifiers and fiber lasers utilizes an active or bare fiber that has a single glass cladding with an outer diameter of less is less than 80 m and preferably less than 60 m or even 40 m. A passive double-clad input fiber is stripped of the outer cladding and tapered to match the outer diameter of the bare fiber. A glass-fluid or glass-vacuum interface along the taper provides guidance of the pump into and along the cladding of the bare fiber and a NA>1 for a vacuum or gasses and an NA>0.8 for liquids. This allows for much shorter fiber lengths to reach max signal power and higher pump conversion efficiencies.

The high-density FAU comprises a support substrate having a grooved front-end section that supports glass end sections of the small diameter low-attenuation optical fibers. A cover is disposed on the front-end section and secured thereto to hold the glass end sections in place. The substrate and the cover can be made of the same glass or glasses having about the same CTE. The glass end sections have a diameter d4 so that the pitch P2 of the fibers at the front end of the FAU can be equal to or greater than d4, wherein d4=2r.sub.4, with r.sub.4 being the radius of the glass end section as defined by the optical fiber cladding. The glass end section has a radius r.sub.4 less than 45 microns, allowing for a high-density FAU and a high-density optical interconnection device.

An optical fiber includes a core region having a relative refractive index profile .sub.1 with a maximum relative refractive index .sub.1max in a range from 0.20% to 0.50%, and a surrounding cladding region that includes a triangular trench cladding region and an outer cladding region, and a relative refractive index .sub.3 with a minimum relative refractive index .sub.3min greater than 0.60% and less than 0.00%, and a trench volume greater than 30% m.sup.2. The outer cladding region has a relative refractive index .sub.4 in a range from 0.01% to 0.06% and a chlorine concentration greater than 1500 ppm. The optical fiber has a mode field diameter at 1310 nm of greater than 9.0 microns, a cable cutoff wavelength of less than 1260 nm, a zero dispersion wavelength between 1300 nm and 1324 nm, and low macrobend loss.

A measurement apparatus, including: a tapered optical fiber, the tapered optical fiber having an input to receive radiation and having an output to provide spectrally broadened output radiation toward a measurement target, the tapered optical fiber configured to spectrally broaden the radiation received at the input; and a detector system configured to receive a redirected portion of the output radiation from the measurement target.

A guidewire having a fiber optic force sensor with a mirror having encoded reflectance is described. The guidewire has a distal housing supported by a core wire. A distal hypotube connected to the distal housing supports a spring intermediate hypotube proximal and distal portions. An atraumatic head is connected to the distal hypotube portion. An optical fiber having at least one fiber core extends through lumens in the core wire and housing to a distal end of the housing. A mirror supported by the atraumatic head faces proximally but is spaced distally from the fiber core at a distal face of the optical fiber. The mirror is provided with a pattern of reflectance that varies along a radius from a central area of reflectance. Light of a defined power shines from the fiber core to the mirror with a reflected percentage of the defined light power being reflected back to the fiber core. A percentage of the reflected percentage of the defined light power is captured by and travels along the fiber core to a light wave detector connected to a controller. From the percentage of the reflected percentage of the light of the defined power received by the detector, the controller is programmed to calculate whether an axial or lateral force is imparted to the atraumatic head and, if so, the magnitude and vector of those forces.

Described and claimed herein are radiation curable compositions for coating an optical fiber, particularly primary coating compositions, wherein the composition possesses specified liquid glass transition temperatures, and/or viscosity ratios between, e.g., 25 C. and 85 C. Such compositions preferably possess large amounts of a reactive oligomer component that is either not substantially derived from, or preferably substantially free from polypropylene glycol, with select diisocyanate constituents, one or more reactive diluent monomers, a photoinitiator, and optionally, one or more additives. Such compositions also are preferably sufficiently viscous at room temperature to ensure optimum optical fiber coating processability. Also described and claimed are methods of using such radiation curable compositions in high speed and/or low helium optical fiber coating applications, along with the coated optical fibers produced therefrom.