Zemax-Based Optimum Structural Design of Probe of an Optical-Fiber Sensor

Bubble plumes are important during the process of air-sea exchange, and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves. This paper designs a new optical-fiber probe (OFP) made of sapphire to overcome the limitations of existing materials (e.g., high brittleness, poor corrosion resistance, and narrow bandwidth) and thereby enhance the detection performance of the OFP by improving its structure. Based on total internal reflection and light refraction, a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips. The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°. Tests are then conducted on a bespoke OFP sensor, the results of which are consistent with those predicted theoretically. The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics. The findings could also be applied to OFPs with multiple tips.