The tracking of small particles is an important but challenging task for biological applications such as disease diagnostics and medical research. Current methods are limited to the use of bulky instruments such as flow cytometers and microscopes. Here, a novel technique for the detection and measurement of micron-scale optical scatterers using a few-mode exposed-core microstructured optical fiber is proposed. Through selective mode launching combined with optical frequency domain reflectometry, scatterers located on the fiber core surface can be simultaneously mapped with both longitudinal and transverse information. This technique is demonstrated by detecting the two-dimensional positions of several femtosecond-laser-inscribed micron-scale ablations written at different locations on the fiber core surface. Due to the compact nature of the optical fiber and its local sensitivity to scatterers that are in close proximity to it, this technique has the potential for the measurement and detection of micron-scale particles in difficult to reach biological environments for in vivo applications.
