An optical waveguide is configured to guide an optical beam, and the optical waveguide includes a down-taper element configured to reduce a diameter of an incoming light beam having a random polarization; a dual-core directional coupler element configured to separate the incoming light beam into a horizontally-polarized beam and a vertically-polarized beam, each beam being confined in first and second cores, respectively; and a core fan-out element configured to increase a distance between the horizontally-polarized beam and the vertically-polarized beam upon exit from the core fan-out element. Each of the down-taper element, the dual-core directional coupler element, and the core fan-out element are 3-dimensional, 3D, printed using a single material.

A gas detector sensor node includes a first sensor conductor having a terminal end, a second sensor conductor including an end section, and a coupler joining the terminal end of the first sensor conductor with the end section of the second sensor conductor. The coupler is permeable to gas.

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.

A non-radial array of microstructure elements provides enhanced wavelength selective filtering. The elements are arranged along a line that does not intersect the center of the core. In this configuration, the first coupling element in an array that is nearest to the core is a non-integer array unit spacing from the main waveguide where the array unit spacing is defined as the flat to flat distance of a hexagonal cell.

An optical rotary joint includes first and second hollow tubular members. At least one of the first and second hollow tubular members is rotatable about a common longitudinal axis. A ring shaped optical waveguide between the first and second hollow tubular members includes first and second axial faces oriented perpendicular to the common longitudinal axis, an inner circumferential edge facing the outer circumference of the first hollow tubular member, an outer circumferential edge facing the inner circumference of the second hollow tubular member, and a circular light scattering channel formed in the first and/or second axial faces. First optical emitters are arranged to face the outer or inner circumferential edge. Second optical emitters are arranged to face the channel. A first optical receiver is arranged to face the outer or inner circumferential edge. A second optical receiver is arranged to face the channel.

A preform element, its production, and fiber production methods from preform assemblies. The preform element has a length and a center axis along its length, a first and second end defined by its length and an outer preform element surface. The preform element includes a plurality of longitudinal structures disposed to form longitudinal hole(s) in a background material. At least one slot extending from its outer preform element surface and intersecting at least one of the longitudinal holes, wherein the at least one slot does not fully intersect the preform element. The preform element may be a preform center element or a preform ring element and may be assembled to a form part of a preform assembly for an optical fiber.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50° C., preferably 50° C.<T.sub.h<250° C.

The invention comprises a delivery fiber assembly suitable for delivering broad band light. The delivery fiber assembly comprises a delivery fiber and a connector member. The deliver has a length, an input end for launching light and a delivery end for delivering light, where the delivery fiber comprises along its length a core region and a cladding region surrounding the core region. The cladding region comprises a cladding background material having a refractive index N.sub.bg and a plurality 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 and 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 is mounted to the delivery fiber at a delivery end section of the delivery fiber comprising said delivery end. The delivery fiber has a transmission bandwidth of about 200 nm or more, such as of about 300 nm or more, such as of about 400 nm or more, such as of about 500 nm or more.

A multicore optical fiber that includes a plurality of waveguiding cores disposed in a cladding. The plurality of cores are situated adjacent to at least one other core with a core center to core center spacing being not larger than 10 times the radius of the average core, such that the greater than 10% of the light will couple from one core to the adjacent core over a propagating distance of 1 cm, along the fiber length so as to provide coupling between the adjacent cores and to enable quantum walk. The plurality waveguiding cores are disposed in the cladding in a ring distribution or at least a portion of the ring distribution.

A multicore optical fiber that includes a plurality of waveguiding cores disposed in a cladding. The plurality of waveguiding cores include one or more first waveguiding cores that have a first propagation constant and one or more second waveguiding cores that have a second propagation constant, where the first propagation constant differs from the second propagation constant. The one or more first waveguiding cores and the one or more second waveguiding cores are disposed in the cladding in a ring distribution and at least a portion of the ring distribution is arranged based on a quasi-periodic sequence having a plurality of sequence segments. Each sequence segment is determined based on a quasi-periodic function, has an order, and corresponds to an arrangement segment of a first waveguiding cores, a second waveguiding cores, or combinations thereof. The ring distribution includes at least one arrangement segment corresponding with a third-order sequence segment or higher of the quasi-periodic sequence.