an apparatus of the present invention is shown in fig2 in that illustration both grating 1 and grating 2 are written at a 34 cross tilted 34 angle of u00b1 u03b8 0 i e one grating oriented at a tilt of u03b8 0 to a perpendicular to the longitudinal axis of the fiber and the other grating tilted at 360 u00b0 u03b8 0 to a perpendicular to the longitudinal axis of the fiber with respect to the vertical i e the latitudinal cross section of a fiber if a shear force is applied along the fiber i e longitudinally in the direction shown in fig2 the tilt angle of grating 1 will increase while that of grating 2 will decrease as shown by the dashed lines in that illustration note that because the direction of this increase and decrease is related to the direction of application of shear force the invention exhibits sensitivity to the direction of application of shear force on the other hand temperature changes will cause changes in u03bb as well as changes in n but these changes will be in the same direction for both grating 1 and grating 2 as a result temperature effects on the present invention are not directional and the bragg shift will be equal and in the same direction for the two gratings if we take the difference of the bragg shifts of the two gratings the temperature effect can be canceled this can be described by the following analysis using the subscripts 34 1 34 and 34 2 34 for gratings 1 and 2 respectively equ5 and u03b4 u03bb u221d u03b4 u03b8 u03b4 u03bb u221d.