## Abstract

An interferometric method to study the induced variations of nonlinear parameters in bent optical fiber such as third-order susceptibility ${\chi}^{(3)}$ and second-order refractive index ${n}_{2}$ is presented. Due to the expected nonlinear response of the Young’s modulus of fiber material, the profiles of asymmetric variations of the two parameters with curvature are observed and calculated, revealing the high spatial and index resolution of the method. The investigation is done in single-mode optical fibers at the standard operating wavelengths of 1300 and $1550\text{\hspace{0.17em}}\mathrm{nm}$ and at radii of curvature from 5 to $11\text{\hspace{0.17em}}\mathrm{mm}$. At the minimum radius of curvature $R=5\text{\hspace{0.17em}}\mathrm{mm}$, the cladding ${\chi}^{(3)}=4.131\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ on the tensile side, whereas on the compressed side it is $4.601\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ for $\lambda =1300\text{\hspace{0.17em}}\mathrm{nm}$. On the tensile side ${n}_{2}=1.09\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$, whereas on the compressed side it is $1.216\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$. For $\lambda =1550\text{\hspace{0.17em}}\mathrm{nm}$, the cladding ${\chi}^{(3)}$ and ${n}_{2}$ on the tensile side are $3.96\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ and $1.055\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$, whereas in the compressed cladding side they are $4.435\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ and $1.174\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$, respectively. At $\lambda =1300\text{\hspace{0.17em}}\mathrm{nm}$ and $R=5\text{\hspace{0.17em}}\mathrm{mm}$, the core ${\chi}^{(3)}$ is given by $4.631\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ on the tensile side and $4.649\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ on the compressed side. The asymmetry in ${n}_{2}$ is given by $1.223\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$ on the tensile side and by $1.227\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$ on the compressed side. With $\lambda =1550\text{\hspace{0.17em}}\mathrm{nm}$, the core ${\chi}^{(3)}$ asymmetry is given by $4.46\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ on the tensile side and by $4.477\times {10}^{-15}\text{\hspace{0.17em}}\mathrm{esu}$ on the compressed side. For ${n}_{2}$ its asymmetry is provided by $1.181\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$ on the tensile side and by $1.185\times {10}^{-13}\text{\hspace{0.17em}}\mathrm{esu}$ on the compressed side.

© 2009 Optical Society of America

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