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 Nbg and a plurality of microstructures in the form of inclusions of solid material having refractive index up to Ninc and extending in the length of the longitudinal axis of the delivery fiber, wherein Ninc<；Nbg. 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.
