Optical fiber sensing allows for remote spectroscopic measurements to be carried out in harsh environments. The entire fiber length may be used for sensing by locating sensor molecules outside of the fiber core; light propagating in the core interacts with the sensor molecules through evanescent fields, which may also capture the sensor-molecule fluorescence and guide it to the detector. Large sensor arrays can be built, with the location of a particular sensor determined by the arrival time of the corresponding fluorescence pulse at the fiber end with respect to the exciting laser pulse. Thus, many different parameters may be monitored simultaneously.

Adjacent sensor regions must be spaced meters apart along a single fiber because the spatial resolution is constrained by the sensor fluorescence lifetimes. Forming an orthogonal junction with an additional fiber, with the second fiber capturing the sensor fluorescence pulses through evanescent fields, allows for greatly reducing the spacing between adjacent regions.

Small displacements, however, between the fibers can result in large signal changes due to the exponential decay of evanescent fields away from the fiber core/cladding interface. Thus, hydrogel resins are unsuitable for sensing in aqueous environments as polymer swelling causes separation of the junction, resulting in weak, inconsistent signals. Here, nanosphere templating was used to create pores in a hydrophobic polymer that allow analyte passage to the evanescent region. Rigid fiber junctions were created from latex nanospheres and Norland optical adhesives. Nanosphere coverages and pore sizes were investigated with SEM imaging, and deposition techniques were compared.