A multiplexed reconfigurable modular FBG-based sensor platform for flow and temperature measurements in the North Sea

In this work a multiplexed multi-parameter marinized sensory array is described. This was deployed in 2 different array configurations across 3 different marine sites in Orkney. The chosen deployment sites were to test the sensory array response to long period oceanic waves, the effects of passing marine traffic for harbor security, and highly energetic tidal flow generation. The sensor array is made up of 4 measurement stations which are connected in series. Across these measurement stations, a total of 16 temperature sensors, 4 attitude sensors (each consisting of 3 individual fiber sensors) and 16 flow sensors were successfully deployed. A total of 86 FBGs were interrogated simultaneously. They were addressed over 0.25km via 20 single-mode (SMF-28e) optical fibers contained in a single marine compliant ruggedized umbilical. The bio-inspired fiber optic flow sensors are designed to mimic the behavior of the superficial neuromasts naturally found as part of the lateral line sensory organ present in fish. The sensor is composed of optical fibers inscribed with Fiber Bragg Gratings glued together in a polymer matrix which are then encapsulated in a polyurethane shell. The sensors response has been tested in DC flows in a tow tank and have demonstrated the ability of measuring flow speed from 0.05ms^-1 to 2.5ms^-1. The main aim of the deployment was to demonstrate the capabilities of fiber sensor technology for oceanographic applications. The measurement periods described lasted over 1 day and the sensor system performed well in comparison with data gathered from commercial instrumentation.