The refractive index of a fiber core of a few mode optical fiber is n1. A cladding layer surrounding the fiber core includes: a downward-concave cladding layer surrounding the fiber core, the refractive index thereof is n2; a first upward-convex cladding layer surrounding the downward-concave cladding layer, the refractive index thereof is n3; a second upward-convex cladding layer surrounding the first upward-convex cladding layer, the refractive index thereof is n4; an outer layer surrounding the second upward-convex cladding layer, the refractive index thereof is n5. The refractive indexes of the fiber core, the downward-concave cladding layer, the first upward-convex cladding layer, the second upward-convex cladding layer, the outer layer satisfy: n.sub.1>n3>n.sub.4>n.sub.5>n.sub.2. The fiber is a non-single mode in a direct waveguide state, and equivalent single-mode transmission can be achieved when the optical fiber is bent at a specific bending radius.

Provided is an optical fiber containing an alkali metal element or the like having a smaller diffusion coefficient than K and having a low Rayleigh scattering loss. An optical fiber is composed of silica glass and includes a core and a cladding arranged to surround the core which has a lower refractive index than the core. The core includes a first core including a central axis and a second core arranged to surround the first core. The average concentration of an alkali metal element or alkaline-earth metal element in the first core is 10 mol ppm or less. The average concentration of chlorine in the first core is 2000 mol ppm or more. The average concentration of an alkali metal element or alkaline-earth metal element in the second core is 10 mol ppm or more. The average concentration of chlorine in the second core is 10 to 600 mol ppm.

The present invention is directed to an optical fiber that includes a glass core region that has nano-sized structures configured to scatter light propagating in the glass core region. The glass core region has an average refractive index n.sub.avg. The fiber includes an interior glass cladding region that has an interior cladding refractive index n.sub.2 that is less than n.sub.avg. The fiber includes an outer cladding region that has an outer cladding refractive index n.sub.3 that is less than n.sub.2. A refractive index difference of n.sub.2n.sub.3 corresponds to a bend uniformity diameter; the light exiting the outer cladding at a fiber bending location is substantially non-uniform when a bending diameter of the fiber bending location is less than the bend uniformity diameter.

A specialized, dispersion-controlled fiber is particularly configured to exhibit a relatively uniform dispersion (D) over a broad spectral range (for example, 1000 nm to 2000 nm). The specialized fiber exhibits an essentially constant attenuation () over this same spectral range so that the fiber is defined as having a high figure of merit (FoM) where FoM is defined as |D|/. The specialized fiber is well-suited for use as a pulse stretcher, providing the ability to separate out wavelength constituents of an extremely short (fs, ps) broadband pulse into the ns range, for example.

A dispersion shifted optical fiber where a radius r.sub.0 of a first center segment is 0.5 m to 2.8 m, and a relative refractive index difference .sub.0 is 0.4% or more and 0.9% or less. A radius r.sub.1 of a first segment is 1.8 m or more and 4.5 m or less. A radius r.sub.2 of a second segment is 4.0 m or more and 8.0 m or less, and a relative refractive index difference .sub.2 is 0.00% or more and 0.07% or less. A radius r.sub.3 of a third segment is 4.5 m or more and 8.5 m or less, and a relative refractive index difference .sub.3 is 0.285% or more and 0.5% or less. A radius r.sub.4 of a fourth segment is 8.0 m or more and 16.0 m or less, and a relative refractive index difference .sub.4 is 0.005% or more and 0.04% or less.

An optical beam delivery device includes: a first length of fiber having a first refractive index profile (RIP) to enable modification of one or more beam characteristics of an optical beam having a first beam shape; an a second length of fiber having at least one beam-shaping confinement region and situated to receive the optical beam from the first length of fiber, wherein the at least one beam shape-modifying confinement region has a quadrilateral cross-section.

A method of tailoring beam characteristics of a laser beam during fabrication of an electronic device. The method includes: providing a substrate comprising one or more layers; adjusting one or more characteristics of a laser beam; and impinging the laser beam having the adjusted beam characteristics on the substrate to carry out at least one process step for fabricating the electronic device. The adjusting of the laser beam comprises: perturbing the laser beam propagating within a first length of fiber to adjust the one or more beam characteristics of the laser beam in the first length of fiber or a second length of fiber or a combination thereof, the second length of fiber having two or more confinement regions; coupling the perturbed laser beam into the second length of fiber; and emitting the laser beam having the adjusted beam characteristics from the second length of fiber.

An optical fiber comprising: (i) a core region comprising an outer radius r.sub.1, and 3.0r.sub.17.0 microns and a relative refractive index .sub.1max and 0.32%.sub.1max0.5%; (b) a depressed index cladding region surrounding the core region comprising an outer radius r.sub.3 and a relative refractive index .sub.3 less than 0.2%, and trench volume V.sub.3 wherein 45% -micron.sup.2|V.sub.3|200% -micron.sup.2; (c) a first outer cladding region surrounding the depressed index cladding region and comprising a relative refractive index .sub.4 and an outer radius r.sub.4; and (d) a second outer cladding layer comprising 5 wt %-20 wt % titania, a relative refractive index .sub.5, and a thickness T.sub.M, wherein 3 micronT.sub.M30 microns, and outer radius r.sub.565 microns; the optical fiber has a mode field diameter MFD.sub.1550 and 8 micronsMFD.sub.155010.5 microns, a cutoff wavelength 1550 nm when bent 1 turn around a 2.5 mm radius mandrel, and a bending loss at 1550 nm when using a mandrel comprising a radius of 2.5 mm of 1.0 dB/turn.

An optical fiber with ultra-low attenuation and large effective-area includes a core layer and cladding layers. The cladding layers have an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary outer cladding layer. The core layer has a radius of 4.8-6.5 m, and a relative refractive index difference of 0.06% to 0.10%. The inner cladding layer has a radius of 9-15 m, and a relative refractive index difference of about 0.40% to 0.15%. The trench cladding layer has a radius of about 12-17 m, and a relative refractive index difference of about 0.8% to 0.3%. The auxiliary outer cladding layer has a radius of about 37-50 m, and a relative refractive index difference of about 0.6% to 0.25%. The outer cladding layer is a pure silicon-dioxide glass layer.

An optical fiber comprising: (i) a core region comprising an outer radius r.sub.1, and 3.0r.sub.17.0 microns and a relative refractive index .sub.1max and 0.32%.sub.1max0.5%; (b) a depressed index cladding region surrounding the core region comprising an outer radius r.sub.3 and a relative refractive index .sub.3 less than 0.2%, and trench volume V.sub.3 wherein 45% -micron.sup.2|V.sub.3|200% -micron.sup.2; (c) a first outer cladding region surrounding the depressed index cladding region and comprising a relative refractive index .sub.4 and an outer radius r.sub.4; and (d) a second outer cladding layer comprising 5 wt %-20 wt % titania, a relative refractive index .sub.5, and a thickness T.sub.M, wherein 3 micronT.sub.M30 microns, and outer radius r.sub.565 microns; the optical fiber has a mode field diameter MFD.sub.1550 and 8 micronsMFD.sub.155010.5 microns, a cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, and a bending loss at 1550 nm when using a mandrel comprising a radius of 2.5 mm of 10 dB/turn.