Optical fiber sensing method for simultaneous measurement of seawater velocity and direction

This Letter presents and demonstrates an optical fiber vector sensor for simultaneous measurement of seawater velocity and direction, which is based on two reflective Panda fiber polarization interferometers orthogonally pasted on a hollow cylindrical cantilever. The general formulas for calculating the velocity and direction of seawater are summarized based on the calibration experiments. Compared with acoustic Doppler velocimetry (ADV), the proposed sensor has the relative error of 5.92% in velocity measurement and 3.47% in direction measurement, which achieves high sensitivity measurement of seawater velocity. The proposed cantilever-type optical fiber vector sensor has the advantages of high sensitivity and arbitrary angle velocity measurement, which is expected to play an important role in the field of ocean velocity measurement.