Comparing free-space and fibre-coupled detectors for Fabry-P\'erot based all-optical photoacoustic tomography

All-optical ultrasound detection bears unique advantages for photoacoustics, including wider detection bandwidth, higher signal-to-noise per unit area and lower susceptibility to electromagnetic noise. These benefits have established optical ultrasound detection as a key method for photoacoustic applications in biology and medicine. However, the use of free-space detectors renders this approach sensitive to optical aberrations, which can degrade the pressure sensitivity and result in deteriorated image quality. While spatial mode-filtering through fibers has been proposed to alleviate these problems in Fabry-P\'erot based pressure sensors, their real functional advantage has never been properly investigated. In this paper we rigorously and quantitatively compare the performance of free-space and fibre-coupled detectors in a custom correlative setup. We demonstrate the superiority of the latter in terms of both signal level and image quality in realistic all-optical photoacoustic tomography settings.