MEG/MRI-compatible optical fiber holder for photodiode

thingiverse

To accurately measure stimulus timing in complex neuroscientific studies, a highly sensitive photodiode attached to the display screen is frequently employed. In order to avoid introducing ferromagnetic interference into MRI-/MEG-chambers, I implemented an innovative solution by routing an optical fiber from the stimulus presentation screen outside of the chamber, where its transmitted brightness was precisely measured via a compact circuit and a specialized Avago SFH250 photodiode connected directly to the MEG acquisition computer. To securely hold the optical fiber in place without twisting or applying tape, I created and 3D-printed this custom glass fiber holder. A high-quality Broadcom 2.2mm plastic optical fiber cable was carefully fed through the central hole and firmly secured at the front using an HFBR-4501Z simplex connector. The optical fiber holder is then effortlessly positioned on the projection screen inside the MEG chamber prior to each experiment, allowing for rapid setup and precise measurements.