Why is there a PCF fibre used in the venteon power oscillator to obtain the beat signal and CEP stabilization?

Some applications require a spectrum with less bandwidth and smoother shape than offered by an octave spanning spectrum but still need CEP stabilization. To fulfil these requirements, the venteon power uses the more traditional approach – using a PCF fibre for spectral broadening, keeping a high power output from the oscillator with a smooth shape, less than octave spanning spectrum, for use in these experiments.

Related to: venteon