Abstract
It is shown that a small slope in the refractive index profile of an optical fiber causes the two lowest order spatial modes to travel different distances from the geometrical center of the fiber. This effect increases by orders of magnitude the bend sensitivity of two-mode fiber modal interferometers, allowing for interesting sensing applications. Good agreement is obtained between the bending sensitivity measured experimentally and calculated using modal perturbation techniques. Some trends relating the bending sensitivity to the shape of the profile's asymmetry are discussed. A temperature and strain compensated bending sensor for bending over arbitrary paths is demonstrated as an application of this technology. Some alternate two-mode fiber bending sensors are presented, including one capable of measuring bending in three dimensions. Finally, some areas of application are discussed.
Covington, Charles Eric (1993). A two-mode fiber optic-bending sensor. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1993 -THESIS -C873.