A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.

Methods are known for producing an anti-resonant hollow-core fiber which has a hollow core extending along a fiber longitudinal axis and an inner jacket region that surrounds the hollow core, said jacket region comprising multiple anti-resonant elements. The known methods have the steps of: providing a cladding tube that has a cladding tube inner bore and a cladding tube longitudinal axis along which a cladding tube wall extends that is delimited by an interior and an exterior; providing a number of tubular anti-resonant element preforms; arranging the anti-resonant element preforms at target positions of the interior of the cladding tube wall, thereby forming a primary preform which has a hollow core region and an inner jacket region; and elongating the primary preform in order to form the hollow-core fiber or further processing the primary preform in order to form a secondary preform. The aim of the invention is to achieve a high degree of precision and an exact positioning of the anti-resonant elements in a sufficiently stable and reproducible manner on the basis of the aforementioned methods. This is achieved in that while further processing the primary preform according to step (c), an external layer cylinder is used which has a radial viscosity profile such that the viscosity increases towards the interior of the external layer cylinder.

An optical sensor that includes a photonic crystal fiber (PCF) and an optical coupler. The PCF includes a hollow core with a first diameter (Dc), an inner cladding section, and an outer layer surrounding the inner cladding section. The inner cladding section includes a cladding material and a plurality of spaced apart circular-shaped channels disposed in the cladding material surrounding the hollow core. The cladding material includes at least one of glass, ceramic, and glass-ceramic. Each spaced apart circular-shaped channel has substantially the same size and an average diameter (d). A first end of the PCF is in optical communication with a light source and a second end of the PCF is in optical communication with the optical coupler.

A robust, rugged, and small hybrid fiber for use in reference chambers was created using a Hollow-Core Photonic Bandgap Fiber (HCPBF). The hybrid fiber and associated chamber apparatus is amenable to mass production and can be used for wavelengths of light from 400 nm to 2000 nm. The apparatus and method of making thereof is described herein.

A microstructured optical fiber includes a core region and a cladding region which surrounds the core region. The cladding region includes a plurality of cladding features within a cladding background material, wherein the cladding region includes an inner cladding region with at least one inner ring of cladding features and an outer cladding region with at least three outer cladding rings of outer cladding features. The inner cladding features have a first characteristic diameter and the outer cladding region includes a plurality of outer cladding features having a characteristic diameter smaller than the first characteristic diameter. The first characteristic diameter is at least about 10% larger than an average diameter of the outer cladding features and the core region has a diameter of at least about 2 ?m.

Rare earth doped fiber lasers can be robust and efficient sources of high quality light, but are usually limited to the highest gain transitions of the active species. But rare earths typically possess a multitude of potentially useful transitions that might be accessed if the dominant transition can be suppressed. In fiber lasers this suppression is complicated by the very high net gain the dominant transitions exhibit; effective suppression requires some mechanism distributed along the length of the fiber. We have developed a novel waveguide with resonant leakage elements that frustrate guidance at well-defined and selectable wavelengths. Based on this waveguide, we have fabricated a Large Mode Area Neodymium doped fiber with suppression of the four-level transition around 1060 nm, and demonstrated lasing on the three-level transition at 930 nm with good efficiency.

A fiber structural body includes a first fiber, and a second fiber spliced to the first fiber such that light having propagated through the first fiber propagates through the second fiber. At least one of the fibers is a photonic crystal fiber. The second fiber is coated with a first coating layer and a second coating layer in order from a splice surface, and the first coating layer has a refractive index n.sub.1 larger than that of a clad layer of the second fiber. In the fiber structural body, L, r, n.sub.1, and NA satisfy a particular relationship.

The invention generally relates to optical fibers, and, more particularly, to hollow-core optical fibers and cables for use in high-speed data transmission, including transmission of telecommunications data, and methods of manufacturing such hollow-core optical fibers and cables.

A method for manufacturing a capillary usable as part of a hollow-core photonic crystal fiber. The method includes obtaining a capillary having capillary wall including a first wall thickness; and chemically etching the capillary wall to reduce the wall thickness of the capillary wall. During performance of the etching, a control parameter is locally varied along the length of the capillary, the control parameter relating to reactivity of an etchant used in the etching, so as to control the etched wall thickness of the capillary wall along the capillary length. Also disclosed is a capillary manufactured by such a method and various devices including such a capillary.

The invention comprises a delivery fiber assembly suitable for delivering broad band light and comprising a delivery fiber and a connector member. The delivery fiber has a length, an input end for launching light and a delivery end for delivering light. The delivery fiber comprises along its length a core region and a cladding region surrounding the core region wherein the cladding region comprises a cladding background material having a refractive index N.sub.bg and a plurality of microstructures in the form of inclusions of solid material having refractive index up to N.sub.inc and extending in the length of the longitudinal axis of the delivery fiber, wherein N.sub.inc<N.sub.bg. The plurality of inclusions in the cladding region is arranged in a cross-sectional pattern comprising at least two rings of inclusions surrounding the core region. The connector member is mounted to the delivery fiber at a delivery end section of the delivery fiber comprising the delivery end. The delivery fiber has a transmission bandwidth of about 200 nm or more.