An all solid hybrid waveguiding structure provides large mode area, acceptable losses of the desired core mode and very high losses of the undesired next higher order mode in the core. Embodiments of the waveguide include a hybrid of low index barriers providing confinement by total internal reflection, and further include high index rings that support guided modes only at effective indices different from that of the desired core mode.

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.

A field of waveguides is disclosed. A tubular electromagnetic waveguide includes a hollow central portion defined by a first set of at least seven primary hollow tubes that are distributed annually about the hollow central portion, and a second set of tubes including at least one secondary hollow tube; when there are a plurality thereof positioned annularly around the primary hollow tubes the area of the at least one secondary hollow tube is comprised between 0.35 and 0.50 times the area of the hollow central portion. The hollow tubes of the first set are substantially of same size and distant from one another.

A mounted hollow-core fiber arrangement includes a hollow-core fiber having a microstructure, and a mount arrangement including a plurality of mounting contacts configured to apply a force to an outer layer of the hollow-core fiber. A portion of the hollow-core fiber is located in a receiving region of the mount arrangement. The plurality of mounting contacts are positioned around the receiving region. The mounting contacts are distributed around the receiving region, the distribution of the mounting contacts corresponding to a distribution of features of the microstructure of the hollow-core fiber. The mounted hollow core fiber can be used in a radiation source apparatus for providing broadband radiation.

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 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.

A terahertz waveguide includes an input segment, a transmission segment and an output segment. The input segment includes an input waveguide and an input microstructured waveguide. One end of the input waveguide is connected with one end of the core of the input microstructured waveguide. The transmission segment includes at least a sub-wavelength waveguide, an air cladding surrounding the sub-wavelength waveguide and a solid outer cladding surrounding the air cladding. The other end of the core of the input microstructured waveguide is connected with one end of the sub-wavelength waveguide. The other end of the sub-wavelength waveguide is connected with the core of the output microstructured waveguide. One end of the solid outer cladding is connected with the cladding of the input microstructured waveguide, and an output segment. The output segment includes an output microstructured waveguide and an output waveguide.

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 terahertz waveguide includes an input segment, a transmission segment and an output segment. The input segment includes an input waveguide and an input microstructured waveguide. One end of the input waveguide is connected with one end of the core of the input microstructured waveguide. The transmission segment includes at least a sub-wavelength waveguide, an air cladding surrounding the sub-wavelength waveguide and a solid outer cladding surrounding the air cladding. The other end of the core of the input microstructured waveguide is connected with one end of the sub-wavelength waveguide. The other end of the sub-wavelength waveguide is connected with the core of the output microstructured waveguide. One end of the solid outer cladding is connected with the cladding of the input microstructured waveguide, and an output segment. The output segment includes an output microstructured waveguide and an output waveguide.