Monte Carlo simulation of SiO2 nanoparticle-coatedpolymer optical fiber humidity sensor by ray tracing

A fiber optic device sensitive to humidity is detailed and modelled by ray tracing based on Monte Carlo simulation. The device is intended primarily for monitoring humidity in the microenvironment of wounds without removing the wound dressing and thus disturbing the wound-healing process. To produce the sensor, cladding is removed from a segment of its polymer-fiber and mesoporous SiO2 nanoparticles are deposited in the exposed zone. This introduces an additional light-transmission loss. The extent of such loss is related to the relative humidity of the environment. Such a relationship, embodying the essence of the sensor’s modulation principle, is examined in this paper by ray tracing based on Monte Carlo simulation. The sensor is explained in detail and its performance is characterised.