  Nowadays fiber biphoton sources are nearly as popular as crystal-based ones.
They offer a single spatial mode and easy integrability into optical networks.
However, fiber sources lack the broad tunability of crystals, which do not
require a tunable pump. Here, we report a broadly tunable biphoton source based
on a suspended core fiber. This is achieved by introducing pressurized gas into
the fibers hollow channels, changing the step index. The mechanism circumvents
the need for a tunable pump laser, making this a broadly tunable fiber biphoton
source with a convenient tuning mechanism, comparable to crystals. We report a
continuous shift of 0.30THz/bar of the sidebands, using up to 25bar of argon.
