Delivery fiber assembly and a broad band source

A source for supplying light, the source comprising:

• a broadband source configured to generate broadband light;
• and
• a microstructured delivery fiber and a connector member, the delivery fiber having a longitudinal axis, an input end for launching light, and a delivery end for delivering light, the connector member being mounted to the delivery fiber at a delivery end section of the delivery fiber, the delivery fiber comprises 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 inclusions of solid material having a refractive index up to Ninc and extending in the direction of longitudinal axis of the delivery fiber, wherein Ninc<Nbg, where the delivery fiber is polarization maintaining, and where the delivery fiber is arranged for receiving at least a portion of the broadband light for delivering at least a part of the received portion of the broadband light.