Record wide all-normal dispersion supercontinuum in cooked fiber

Supercontinuum generation in the normal dispersion regime, also known as ANDi-SCG, yields excellent noise properties but limited spectral broadening. We show that we can double the output spectral width by embedding a short section of anomalous dispersion fiber, resulting in an in-fiber pulse compression before the supercontinuum generation. We implement the anomalous section without splices, by controlled thermal exposure of a single normal dispersion fiber: diffusing the core dopants allows to locally switch the sign of the dispersion. We then use such a fiber to demonstrate a record wide ANDi supercontinuum from 1060 to 2700nm.