Side-emitting optical fibers (SEOFs) offer a promising approach for delivering germicidal Ultraviolet-C (UV–C) light to complex surfaces in water systems (e.g., tubing, curved surfaces) where biofilms can grow. However, SEOFs typically exhibit nonuniform irradiance along their length, complicating system design. To enable efficient design of UV–C SEOFs, we characterized the spatial irradiance of a 280 nm light-emitting diode (LED) coupled to an SEOF. Irradiance along the fiber length was measured in air using a calibrated spectrometer, and total side-emitted optical power was quantified in water using chemical actinometry. A two-dimensional, first-principles ray-tracing simulation was developed to model light propagation, entry, emission, and loss from the LED through the SEOF. The simulation successfully predicts experimental values of the in-air irradiance trend within the 5th-95th percentile of each datum and the total in-water side-emitted power (within 6.4% error of the experimental average). We predicted otherwise unmeasurable under-water irradiance delivered to a surface by applying the simulation to a prior biofilm inhibition study in a pressurized water-filled reactor. The open-source code is available for broader use. Our findings advance the design of UV–C delivery systems by improving the understanding of irradiance distribution on treatment surfaces when the fiber is submerged, enabling more effective deployment of SEOFs in water treatment applications.
Shapiro et al. (Mon,) studied this question.