MEG/MRI-compatible optical fiber holder for photodiode

thingiverse

To precisely determine stimulus timing in neuroscientific experiments, a photodiode attached to the screen is often used. As running ferromagnetic cables into MRI-/MEG-chambers should be avoided, I installed an optical fiber running from the stimulus presentation screen out of the chamber, where the transmitted brightness was measured via a small circuit and an Avago SFH250 photodiode connected to the MEG acquisition computer. To hold the optical fiber to the screen in our CTF275 MEG without twisting or taping, I designed and printed this glass fiber holder. A Broadcom 2.2mm plastic optical fiber cable was fed through the hole and secured at the front part using an HFBR-4501Z simplex connector. The optical fiber holder is then put on the projection screen inside the MEG chamber for each experiment. That way, the optical fiber can quickly be installed before each experiment.