Deformation of single-mode optical fibers under static longitudinal stress

The deformation of single-mode fibers resulting from a longitudinally applied static force has been measured experimentally by means of high resolution heterodyne interferometry and analyzed theoretically using the second-order theory of elasticity and the photoelastic effect. Both the elongation of the fiber and the phase change of light propagating through the fiber have been measured as a function of tensile force. The values of the elastic constants measured for fibers with pure silica core and B
2
O
3
doped cladding are
E = 6.41 \times 10^{10}
N/m
²
for the Young's modulus,
\delta = -4.0
for the nonlinearity constant of the longitudinal strain, and
\beta = -2.3
for the nonlinearity constant of the transverse strain. For unit elongations up to 0.3 percent, no creep, hysterisis, or relaxation effects have been observed within a resolution of one part in 10
⁴
.