An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications

Abstract

Abstract:A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of~0.020 m).

Underwater Depth and Temperature Sensing Based on Fiber Optic Technology for Marine and Fresh Water Applications

“…The FBG temperature sensor was also calibrated and its sensitivity determined to be 12.5 $\mathrm{normalp}\mathrm{normalm}/\mathrm{normalK}$ with a resolution of 0.1 ${}^{\circ }\mathrm{normalC}$ [29]. The OFPTS sensor was then mounted on a CTD rosette frame on the opposite side of the frame to the reference sensor and approximately at the same height as the reference sensor as illustrated in Figure 3.…”

“…Before deployment on the CTD rosette for sea water measurements, the EFPI pressure sensor was calibrated and its sensitivity and resolution determined to be 15 and 0.8 H O respectively. The FBG temperature sensor was also calibrated and its sensitivity determined to be 12.5 with a resolution of 0.1 [ 29 ]. The OFPTS sensor was then mounted on a CTD rosette frame on the opposite side of the frame to the reference sensor and approximately at the same height as the reference sensor as illustrated in Figure 3 .…”

Review of Fiber Optical Sensors and Its Importance in Sewer Corrosion Factor Analysis

“…As glass-based silica is predominantly used for the fabrication of FOS, it provides ultimate resistance towards corrosion and withstands explosive atmosphere without compromising its sensing performance [163]. A FBG-based temperature sensor along with Fabry Perot Interferometer (FPI) used as pressure sensor was realized with remote operated vehicle for ocean environment [164]. Optical temperature sensor based on grating was developed to deploy in sewage tank and it shows good performance over the period greater than year [7].…”

Design and Performance Evaluation of a “Fixed-Point” Spar Buoy Equipped with a Piezoelectric Energy Harvesting Unit for Floating Near-Shore Applications

“…The most sophisticated devices employ energy recovery systems for self-maintenance (e.g., energy harvesting), so that they can be used offshore [ 5 ]. Observation platforms include various types: on site, equipped with remote instrumentation, operating on the surface (on board an oceanographic ship [ 6 ], surface buoys [ 7 , 8 ], floating buoys [ 9 , 10 ], buoys towed by boats [ 11 ]), active on the seabed (autonomous underwater vehicles AUV [ 12 ], remote control vehicles ROV [ 13 ], networks of underwater buoys [ 14 ]), and with satellite monitoring [ 15 ]. Usually, piezoelectric patch transducers (PPTs) are employed as both actuators [ 16 ], to convert electrical voltage into strain, and sensors, in order to measure displacements and strains [ 17 ].…”