Spatially Resolved Pressure Measurement of Antiresonant Hollow-Core Fibres Using Nonlinear Optics

Hollow-core optical fibres (HCFs) guide light in an air-filled hole and exhibit lower loss, lower optical nonlinearity, and lower latency than solid fibres. Pressurising the fibre core with bespoke gases allows for tunability of chromatic dispersion and nonlinearity. Likewise, evacuation of the HCF core can further reduce nonlinearity and phase noise for high power transmission and ultra-stable interferometry, respectively. For these applications, methods to measure the pressure inside the HCF are needed; for example, studies using OTDR have achieved 1.5 m spatial resolution [1]. Here, we numerically investigate pressure measurements via four-wave mixing (FWM) and cross-phase modulation (XPM).