Sensitivity of Birefringent Microstructured Polymer Optical Fiber to Hydrostatic Pressure

We present a PMMA birefringent fiber with enhanced polarimetric sensitivity to hydrostatic pressure, obtained by enlarging selected holes in the microstructured cladding. The fiber shows a linear response to pressure with small hysteresis in the pressure range up to 8.5 MPa and the sensitivity of 48 ${\rm rad}/{\rm MPa}\cdot{\rm m}$ at 600 nm. The average temperature sensitivity measured in the range 22–40 $^{\circ}{\rm C}$ is 1 ${\rm rad}/{\rm K}\cdot{\rm m}$ at 600 nm. The fiber, however, shows significant hysteresis increasing with the temperature range. We also present the results of numerical simulations of the birefringence and the sensitivity to pressure. The contribution of stress and deformation effects to the overall pressure sensitivity in the investigated PMMA fiber and the silica fiber of the same geometry is compared. This allows us to explain different signs of pressure sensitivity observed in silica and the PMMA fibers.