All fiber torsion and displacement sensor based on image detection

We propose an all-fiber-optic sensor for simultaneous rotation and displacement measurement based on elastic-optic effect in a dual mode fiber. LP01 and LP11 modes are both excited in the fiber and are distinguished using wavelength-scanning Spatially and Spectrally resolved imaging technique (S2 Imaging) to accomplish rotation and displacement detection. Mode rotation is characterized by the LP11 mode rotation using elastic-optic theory; a displacement area of 120 × 120 μm is detected and measured by recording the trace of LP01 mode pattern. Balance between the detection range and resolution of the sensor is adjustable by simply changing the fiber length or adjusting the relative position of fiber-end, lens and the CCD camera. Real-time detection at ∼0.5 s per measurement speed is achieved, and twist rate and moving velocity can also be measured.