A single mode optical fiber including a germania doped silica central core region having outer radius r.sub.1 and refractive index .sub.1, a maximum refractive index .sub.1max, and 0.32%.sub.1max0.45%, and a core alpha profile (Core.sub.). In various embodiments, the optical fiber also contains a cladding region including: (i) a second inner cladding region or ring region surrounding the first inner cladding region; or (ii) an inner cladding region or pedestal region surrounding the germania doped silica central core region. The corresponding resultant optical fibers exhibit a 22 m cable cutoff less than or equal to 1260 nm, a macrobending loss at 1550 nm of 0.75 dB/turn on a 20 mm diameter mandrel, a zero dispersion wavelength, .sub.0, of 1300 nm.sub.01324 nm, and a mode field diameter at 1310 nm of 8.2 micronsMDF.sub.1310 nm9.6 microns.

The invention concerns a method for generating a laser beam (3) with different beam profile characteristics, whereby a laser beam (2) is coupled into one fiber end (1a) of a multi-clad fiber (1), in particular a double-clad fiber, and emitted from the other fiber end (1b) of the multi-clad fiber (1) and whereby, to generate different beam profile characteristics of the output laser beam (3), the input laser beam (2) is electively coupled either at least into the inner fiber core (4) of the multi-clad fiber (1) or at least into at least one outer ring core (6) of the multi-clad fiber (1), as well as a corresponding arrangement (10).

An optical fiber having both low macrobend loss and low microbend loss. The fiber has a central core region, a first (inner) cladding region surrounding the central core region and having an outer radius r.sub.2>16 microns and relative refractive index .sub.2, and a second (outer) cladding region surrounding the first cladding region having relative refractive index, .sub.3, wherein .sub.1>.sub.3>.sub.2. The difference between .sub.3 and .sub.2 is greater than 0.12 percent. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r.sub.1/r.sub.2 is greater or equal to 0.24 and bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn.

In various embodiments, the beam parameter product and/or numerical aperture of a laser beam is adjusted utilizing a step-clad optical fiber having a central core, a first cladding, an annular core, and a second cladding.

An optical fiber includes: a core; a cladding layer that is lower in refractive index than the core; and a depressed layer that lies between the core and the cladding layer and that is lower in refractive index than the cladding layer, wherein: the optical fiber has an effective core area Aeff that is equal to or greater than 100 ?m.sup.2 and equal to or less than 129 ?m.sup.2, the core has a radius r1 that is equal to or greater than 5.2 ?m and equal to or less than 7.4 ?m, the core has a refractive index volume Vcore that is equal to or greater than 8.5% ?m.sup.2 and equal to or less than 16.5% ?m.sup.2, the depressed layer has a refractive index volume Vdep that is equal to or greater than ?40% ?m.sup.2 and less than 0% ?m.sup.2.

An optical fiber comprises, from a center to a periphery, a fiber core of undoped silica; a cladding layer; and a coating of polyacrylate, wherein the fiber core has a radius of 5 to 7 m and an ellipticity of less than 1.5%, the cladding layer with an ellipticity of less than 0.4% comprises inner, intermediate, and outer cladding layers, the inner cladding layer being doped with fluorine of 5 to 12 m thickness, and refractive index difference to fiber core of 0.4 to 0.2%, the outer cladding layer being undoped quartz of 25 to 45 m thickness, and the coating comprises an inner coating of 25 to 40 m thickness, and an outer coating of 25 to 35 m thickness and an ellipticity of less than 2%. The optical fiber has high durability and large effective transmission area, a method and system for preparing such optical fiber are also disclosed.

An optical fiber includes (i) a chlorine doped silica based core having a core alpha (Core.sub.)4, a radius r.sub.1, and a maximum refractive index delta .sub.1 max% and (ii) a cladding surrounding the core. The cladding surrounding the core includes a) a first inner cladding region adjacent to and in contact with the core and having a refractive index delta .sub.2, a radius r.sub.2, and a minimum refractive index delta .sub.2 min such that .sub.2 min<.sub.1 max, b) a second inner cladding adjacent to and in contact with the first inner cladding having a refractive index .sub.3, a radius r.sub.3, and a minimum refractive index delta .sub.3 min such that .sub.3 min<.sub.2, and c) an outer cladding region surrounding the second inner cladding region and having a refractive index .sub.5, a radius r.sub.max, and a minimum refractive index delta .sub.3 min such that .sub.3 min<.sub.2. The optical fiber has a mode field diameter MFD at 1310 of 9 microns, a cable cutoff of 1260 nm, a zero dispersion wavelength of 1300 nmzero dispersion wavelength1324 nm, and a macrobending loss at 1550 nm for a 20 mm mandrel of less than 0.75 dB/turn.

An optical fiber includes a core, a depressed inner cladding surrounding the core, and an outer cladding surrounding the inner cladding, where a refractive index profile of the core includes an power distribution in which an index is 3.5 or more and 6 or less, a relative refractive index difference .sup. of the inner cladding with respect to the adding is set such that an absolute value |.sup.| thereof is 0.01% or more and 0.045% or less, a radius r1 of the core and an outer circumference radius r2 of the inner cladding are set such that a ratio r1/r2 thereof is 0.2 or more and 0.6 or less, a cable cutoff wavelength .sub.cc of 22 m is 1260 nm or less, and a mode field diameter MFD at a wavelength of 1310 nm is 8.6 m or more and 9.5 m or less.

An optical fiber with low attenuation and methods of making same are disclosed. The optical fiber has a core, an inner cladding surround the core, and an outer cladding surrounding the inner cladding. The outer cladding is chlorine-doped such that the relative refractive index varies as a function of radius. The radially varying relative refractive index profile of the outer cladding reduces excess stress in the core and inner cladding, which helps lower fiber attenuation while also reducing macrobend and microbend loss. A process of fabricating the optical fiber includes doping an overclad soot layer of a soot preform with chlorine and then removing a portion of the chlorine dopant from an outermost region of the overclad soot layer. The soot preform with the modified chlorine dopant profile is then sintered to form a glass preform, which can then be used for drawing the optical fiber.

A space-division multiplexed optical fiber includes a relatively high refractive index optical core region surrounded by alternating regions of relatively low and relative high refractive index material, forming concentric high index rings around the core. The optical core region supports propagation of light along at least a first radial mode associated with the optical core region and a high index ring region supports propagation of light along at least a second radial mode associated with the high index ring region. The second radial mode is different from the first radial mode.