In some implementations, a waveguide may comprise an inner core to receive a first beam and an outer core surrounding the inner core to receive a second beam that is displaced from the first beam by an offset. The outer core may comprise a beam guiding region that rotationally expands over a length of the waveguide into an annulus that concentrically surrounds the inner core or a partial annulus that partially surrounds the inner core. For example, the beam guiding region may be defined by one or more low refractive index features that have a varied orientation and/or a varied shape over the length of the waveguide such that the second beam enters the waveguide as an offset beam and exits from the waveguide as a ring-shaped beam or a partial ring-shaped beam.

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 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.

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 low-crosstalk large-capacity few-mode optical fiber includes an optical fiber cladding. Few-mode units are arranged in the optical fiber cladding, each few-mode unit sequentially includes a few-mode fiber core, an inner cladding and a trench from inside to outside, and a high-refractive-index ring is arranged in the few-mode fiber core. The few-mode units include first few-mode subunits, second few-mode subunits and third few-mode subunits, where the first few-mode subunits, the second few-mode subunits and the third few-mode subunits are arranged at intervals. The first few-mode subunit includes a first few-mode fiber core, the second few-mode subunit includes a second few-mode fiber core, and the third few-mode subunit includes a third few-mode fiber core, the radii and refractive indexes of the first few-mode fiber cores, the second few-mode fiber cores and the third few-mode fiber cores being different, respectively.

Optical transmission systems and methods are disclosed that utilize a QSM optical fiber with a large effective area and that supports only two modes, namely the fundamental mode and one higher-order mode. The optical transmission system includes a transmitter and a receiver optically coupled by an optical fiber link that includes at least one section of the QSM optical fiber. Transmission over optical fiber link gives rise to MPI, which is mitigated using a digital signal processor. The QSM optical fiber is designed to have an amount of DMA that allows for the digital signal processor to have reduced complexity as reflected by a reduced number of filter taps as compared to if the DMA were zero.

An optical fiber assembly is provided including an optical fiber and a beam shaping component affixed to an extremity of the optical fiber. The optical fiber supports a guided mode having a spatial profile defining a first shape. The beam shaping component defines a light path and has a transversal refractive index profile including an outer refractive index value greater than an inner refractive index value. The beam shaping component transforms the spatial profile of a light beam propagating along the light path between the first shape and a second shape different from the first shape. The optical assembly may for example transform a Gaussian light beam into a flat-top or donut shape.

The MCF of the present disclosure suppresses XT and leakage loss at 1.565 μm or 1.625 μm for bidirectional communication. The MCF comprises 12 core units each including a core and a depressed layer, a common cladding, and a resin coating. The units are arranged so that no adjacent relationship is established between cores each having an adjacent relationship with a specific core selected from the units, and are arranged so that centers of the units are line symmetric with a symmetry axis intersecting with the central axis and passing through none of the centers of the units. The resin coating's diameter is 250±15 μm, an effective area at 1.550 μm is 70 μm.sup.2 or more, and a 22 m-length cable cutoff wavelength is 1.530 μm or less. A center-to-center interval between adjacent cores, a shortest distance from the core center to the cladding interface, and a cladding's diameter satisfy specific conditions.

An optical fiber system exploits a principle of topological confinement for guided higher-order modes, in contrast to more conventional total-internal-reflection (TIR) confinement. The optical fiber has a geometry and index profile defining a cutoff wavelength for a predetermined L-mode of optical signal propagation in the optical fiber, where L is azimuthal mode index. An optical source subsystem is coupled to the optical fiber to establish an optical signal propagating in the optical fiber, wherein the optical signal has the predetermined L-mode and a wavelength being either (1) at least 15% above the cutoff wavelength such that the optical beam propagates as a topologically confined mode, or (2) sufficiently above the cutoff wavelength that, based on the L-mode of the optical beam, the optical beam propagates as a topologically confined mode having propagation loss less than 3 dB/meter.