A rare earth-doped double-clad optical fiber includes a rare earth ion-doped fiber core, an inner cladding layer, and an outer cladding layer. A cross section of the inner cladding layer is a non-circular plane including at least two arcuate notches. According to the provided optical fiber, optical processing can be performed on a preform without changing a preform preparation process and a drawing process. The inner cladding is designed to have a non-circular planar structure having a cross section with at least two arcuate notches. While maintaining the same light absorption efficiency of pump light within the cladding layer, a preform polishing process is simplified, a risk of cracking the preform during polishing of multiple surfaces and a risk of contamination of the preform caused by impurities are reduced, wire drawing control precision is better, and comprehensive performance of the optical fiber is improved.

A hollow core photonic crystal fiber (PCF) comprising an outer cladding region and 7 hollow tubes surrounded by the outer cladding region. Each of the hollow tubes is fused to the outer cladding to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region. The hollow tubes are not touching each other, but are arranged with distance to adjacent hollow tubes. The hollow tubes each have an average outer diameter d2 and an average inner diameter d1, wherein d1/d2 is equal to or larger than about 0.8, such as equal to or larger than about 0.85, such as equal to or larger than about 0.9. Also a laser system is disclosed.

Described are optical fibers and scanning fiber displays comprising optical fibers. The disclosed optical fibers include a plurality of mass adjustment regions, such as gas-filled regions, positioned between a central waveguiding element and an outer periphery for reducing a mass of the optical fiber as compared to an optical fiber lacking the plurality of mass adjustment regions.

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.

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.

An interferometric optical fibre sensor comprises optical fibre defining an optical circuit configured to propagate a first optical wave via an environment in which the optical fibre can be exposed to a stimulus that modifies the first optical wave, and a second optical wave, and to combine the first optical wave and the second optical wave to create an interference signal containing information about the stimulus, wherein optical fibre propagating either or both of the first optical wave and the second optical wave comprises hollow core optical fibre configured to propagate the optical wave or waves by an antiresonant optical guidance effect.

A hollow-core anti-resonant-reflecting fibre (HC-AF) includes a hollow-core region, an inner cladding region, and an outer cladding region. The hollow-core region axially extends along the HC-AF. The inner cladding region includes a plurality of anti-resonant elements (AREs) and surrounds the hollow-core region. The outer cladding region surrounds the inner cladding region. The hollow-core region and the plurality of AREs are configured to provide phase matching of higher order hollow-core modes and ARE modes in a broadband wavelength range.

An electromagnetic waveguide, such as an optical fibre, including a hollow central core surrounded by a microstructured sheath formed by an assembly of elementary cells, the microstructured sheath also including at least two elementary cells, at least one intermediate element connecting the elementary cells, the intermediate element having a cross-section with an area less than or equal to 50% of the cross-sectional area of each of the cells that it connects, the intermediate element having a refractive index less than or equal to the refractive index of each of the elementary cells that it connects.

The present disclosure relates to an optical fiber with shaped photosensitivity profile, comprising a nanostructured core composed of at least two types of glass rods, wherein at least one type of glass rods is doped with germanium. The invention relates also to a method for preparing an optical fiber with a core allowing for obtaining photoinduced refractive index modulation. Depending on their specific type, such optical fibers are applicable i.a. in laser generation and in amplification techniques (active optical fibers) and/or in optical fiber sensors and telecommunications applications (passive optical fibers).

Described are optical fibers and scanning fiber displays comprising optical fibers. The disclosed optical fibers include a plurality of mass adjustment regions, such as gas-filled regions, positioned between a central waveguiding element and an outer periphery for reducing a mass of the optical fiber as compared to an optical fiber lacking the plurality of mass adjustment regions.