Abstract: A photonic crystal fibre includes a core region for propagating light in a longitudinal direction of the fibre, a cladding region surrounding the core region, the cladding region including micro-structural elements extending in the longitudinal direction. The cladding region further includes at least one stress element having a coefficient of thermal expansion ?T,SAP and extending in the longitudinal direction of the photonic crystal fibre, the stress element(s) being located in a cladding background material having a coefficient of thermal expansion ?T,cladback different from ?T,SAP. The location of the at least one stress element relative to the core region and the micro-structural elements and the coefficients of thermal expansion ?T,SAP and ?T,cladback are adapted to provide a stress induced birefringence in the core region of the photonic crystal fibre. An article includes a photonic crystal fibre, a method of manufacturing and the use of a photonic crystal fibre are furthermore provided.

Abstract: An optical fibre having a longitudinal direction and a cross-section perpendicular thereto, said fibre in a cross-section comprising: (a) a core region (11) having a refractive index profile with a highest refractive index nc, and (b) a cladding region comprising cladding features (10) having a centre-to-centre spacing, ?, and a diameter, d, of around 0.4? or larger, wherein nc, ? and d are adapted such that the fibre exhibits zero dispersion wavelength of a fundamental mode in the wavelength range from 1530 nm to 1640 nm; a method of producing such a fibre; and use of such an optical fibre in e.g. an optical communication system, in an optical fibre laser, in an optical fibre amplifier, in an optical fibre Raman amplifier, in a dispersion compensator, in a dispersion and/or dispersion slope compensator.

Abstract: A microstructured optical fibre comprising an inner cladding and an outer cladding; said outer cladding comprising elongated outer cladding features extending in an axial direction of the fibre, and at least one cladding recess extending at least partly through the outer cladding in a radial direction to the inner cladding; said cladding recess providing optical access to the inner cladding; a method of forming a cladding recess in such an optical fibre comprising a step of collapsing a part of the outer cladding features by use of a heat source; an apparatus comprising such a microstructured optical fibre, preferably a laser or an amplifier.

Abstract: An optical fibre for transmitting light, said optical fibre having an axial direction and a cross section perpendicular to said axial direction, said optical fibre comprising: (1) a first core region comprising a first core material having a refractive index Nco,1; (2) a microstructured first cladding region surrounding the first core region, said first cladding region comprising a first cladding material and a plurality of spaced apart first cladding features or elements that are elongated in the fibre axial direction and disposed in the first cladding material, said first cladding material having a refractive index Ncl,1 and each said first cladding feature or element having a refractive index being lower than Ncl,1, whereby a resultant geometrical index Nge,cl, 1? of the first cladding region is lowered compared to Ncl,1; (3) a second core region surrounding said first cladding region, said second core region comprising a second core material having a refractive index Nco,2, and (4) a second cladding regio