Theoretical analysis of seawater depth and temperature measurement with C-type micro-structured fiber grating

摘要

A new C-type micro-structured grating structure was proposed for simultaneous measurement of depth and temperature in seawater. Because wedge-shaped defects got introduce, high birefringence was excited at fiber core of grating. Thermo sensitive materials filled in micro pores to improve the sensitivity of temperature. Then we established a mathematical model of birefringence effect in C-type structure. This work analyzed stress distribution in all directions under two disturbances. In pressure and temperature environment, reflection peaks in two-polarization states separated with a large offset Two characteristic parameters: lambda(B, y) - lambda(B, x), lambda(B, y) + lambda(B, x) were proposed for corresponding measurement Structural parameters got optimize for better performance. Calculated output signals had high sensitivity and linearity under pressure range of 0-10 MPa and temperature range of 0-40 degrees C. lambda(B, y) - lambda(B, x) mainly responded to pressure, which got sensitivity - 1.709 nm/MPa. While temperature mainly influenced lambda(B, y) + lambda(B, x) and the obtained temperature sensitivity was 1.054 nm/degrees C. This structure would have a great potential application due to the mature demodulation technique of grating signal.