Gradient Index Fiber Optic Microprobes for Minimally Invasive in vivo Low Coherence Interferometry

We describe design, construction, and application of the smallest fiber optic probes used to date during imaging or diagnosis involving low coherence intereferometry (LCI). The probes use novel fiber optic gradient index (GRIN) lenses fabricated by a recently developed modified chemical vapor deposition (MCVD) process that avoids on-axis aberrations commonly marring MCVD- fabricated GRIN substrate. 

Fusing GRIN fiber lenses onto single mode fiber yields allfiber probes that are automatically aligned and that insert into tissue through hypodermic needles as small as 31-gauge (inner diameter, 127 mm). We demonstrate use of such probes with LCI by measuring microscopic brain motions in vivo.