Acoustic coefficients of P₂O₅-doped silica fiber: The strain-optic and strain-acoustic coefficients

We present measurements and modeling of the effect of P₂O₅ doping on the strain sensitivity coefficients of silica fibers. In particular, the Brillouin gain spectrum of a heavily P₂O₅-doped fiber is measured and investigated at different strains. We provide measurements of the strainoptic coefficient (SOC) and the strain-acoustic coefficient (SAC), obtained to be + 0.139 and + 9854m/sec/ε, respectively, both of which are less than the pure silica values. The Pockels' coefficients p₁₁ and p₁₂ for bulk P₂O₅ are also estimated via Brillouin gain measurements. Using the strain coefficients, the modeled and unique slopes of the Stokes'-shift-versusstrain curves for the four observed acoustic modes in the fiber each lie within 2% of the measured values.