In various embodiments, the beam parameter product and/or beam shape of a laser beam is adjusted by coupling the laser beam into an optical fiber of a fiber bundle and directing the laser beam onto one or more in-coupling locations on the input end of the optical fiber. The beam emitted at the output end of the optical fiber may be utilized to process a workpiece.

A method of measuring a diameter of a core portion of an optical fiber preform including the core portion having a relatively high refractive index and a clad portion having a relatively low refractive index. The method includes applying parallel light to the optical fiber preform, and measuring the diameter of the core portion from an image captured by receiving the light having transmitted through the optical fiber preform.

T/C, which is a ratio of an area T of a skirt part outside the boundary to an area C of the core region in a refractive index distribution, is 4% or more and 30% or less, the boundary is defined at a position where an absolute value of a change amount of the index becomes maximum between the center of the core region and the outer peripheral part of the first clad region, the area C of the core region is defined in a range from the center of the core region to the boundary in the radial direction, the area T of the skirt part is defined in a range from the boundary to the outer peripheral part of the first clad region.

A fiber optic coupling device comprises an elastomeric body. The elastomeric body includes first and second sides with a deformable alignment passage extending there between. The deformable alignment passage is configured to elastically center opposing first and second optical fibers. The deformable alignment passage includes a first portion that is configured to receive the first optical fiber having a first core. The deformable alignment passage also includes an opposing second portion that is configured to receive the second optical fiber having a second core. The first portion and the opposing second portion of the alignment passage are defined by a common encompassing periphery, and meet at a common location within the alignment passage to present the core of the received first optical fiber in coaxial alignment with the core of the received second optical fiber.

An MCF cable according to an embodiment contains a plurality of MCFs each including at least one coupled core group and a common cladding. is set such that at a wavelength of 1550 nm is falls within a range of from 110.sup.1 [m.sup.1] to 110.sup.3 [m.sup.1], and ((3AC.sub.avg)/(2.sup.-K) or (C.sub.f)/(2) is set in a specific range in a wavelength band of from 1530 nm to 1625 nm, where C.sub.avg [m.sup.1], C.sub.f [m.sup.1], and f.sub.twist [turn/m] represent the average curvature, the pseudo-curvature, and the average torsion, respectively, for each MCF, and [m.sup.1], [m.sup.1], and [m] represent the coefficient of mode coupling between adjacent cores, the average of propagation constants, and the core center-to-center distance, respectively.

A few-mode optical fiber including a core's refractive-index profile n(r) of trapezoid-like shape. The optical core having a center part of radius R1 and a transition part ranges from the radius R1 to a radius R2, such that R2>R1 with R2 between 6.8 and 11.5 m, said refractive-index profile being defined by a surface integral of the core index profile of between 18010.sup.3 and 27010.sup.3 m; a transition slope S of between 1.710.sup.3 and 1210.sup.3 m.sup.1; with n1 and n2 the refractive-index difference respectively of the center part of the optical core and of the cladding part adjacent to the optical core, with respect to the outer optical cladding.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

A method of manufacturing a tuned optical fiber includes providing a first preform from a set of like preforms each having substantially the same refractive index profile, including amount of axial variation relative to a target refractive index profile. The method includes drawing a reference optical fiber from the first preform and measuring a variation in an optical or physical property as a function of axial position. The method also includes drawing from a second preform from the set of like preforms the tuned optical fiber. The drawing includes using a time-varying tension that reduces the amount of variation of the optical or physical property of interest. The time-varying tension is defined by an amount of axial stress imparted to the tuned fiber needed to alter the refractive index profile and the at least one optical or physical property based on a stress-optic effect.

An optical fiber for converting a Gaussian laser beam into a Bessel laser beam may include a first segment optically coupled to a second segment with a transition region, the first segment having a first outer diameter greater than a second outer diameter of the second segment. The first segment may include a first core portion with a first cladding portion extending around the first core portion. The second segment may include a second core portion with a second cladding portion extending around the second core portion. The optical fiber may have a non-axisymmetric refractive index profile or may be coupled to an end cap with a non-axisymmetric refractive index profile.

Disclosed herein are methods, apparatus, and systems for providing an optical beam delivery system, comprising an optical fiber including a first length of fiber comprising a first RIP formed to enable, at least in part, modification of one or more beam characteristics of an optical beam by a perturbation assembly arranged to modify the one or more beam characteristics, the perturbation assembly coupled to the first length of fiber or integral with the first length of fiber, or a combination thereof and a second length of fiber coupled to the first length of fiber and having a second RIP formed to preserve at least a portion of the one or more beam characteristics of the optical beam modified by the perturbation assembly within one or more first confinement regions. The optical beam delivery system may include an optical system coupled to the second length of fiber including one or more free-space optics configured to receive and transmit an optical beam comprising the modified one or more beam characteristics.