The invention relates to the field of light sources and in particular to sources of light of wavelengths extending across a broad spectrum of hundreds of nanometres. An object of the invention is to provide a relatively compact and inexpensive source of light of wavelengths spread over a broad spectrum. The light source comprises a laser (4) , which operates at or near its fundamental wavelength and produces pulses of a duration longer than 0.5 ns, and a micro-structured optical fibre (9) arranged to guide the pulses, wherein the light is generated by the pulses in the fibre (9) . The invention further relates to a method of generating a light of a spectrum. The invention may be useful in applications such as spectral testing of fibre components and spectral analysis of chemical and biological samples.