Global overview of the sensitivity of long period gratings to strain

• Statistical study on the influence of strain on the cladding modes of a LPG.
• The cross sensitivity to axial and radial strain can generally be neglected.
• It exists a linear correlation between the sensitivities to axial and radial strain.
• Highest sensitivities are obtained with smallest claddings and periods.
• Highest coupling coefficients are obtain with smallest claddings and periods.

This paper presents the results of a statistical study of the influence of radial and axial strain on the cladding modes of long period gratings (LPG). Ten thousand gratings were randomly chosen in a parameter space and their sensitivities to strain in the range [−1000 μϵ; +1000 μϵ] were calculated. Cross-sensitivity to axial and radial strain was found to be generally very weak and can be neglected. However, a linear correlation between the sensitivities to axial and radial strain was found. The greatest sensitivities to axial strain were found in the range −0.55 pm/μϵ to −2 pm/μϵ and to radial strain between −0.3 pm/μϵ and 0.5 pm/μϵ. The absolute values of the sensitivities to axial and radial strain were found to decrease with the cladding radius and the grating period. The coupling coefficient is slightly affected by the strain. The LPGs with the smallest claddings and smallest periods exhibited the highest coupling coefficient and the highest sensitivities to strain.