Radiation effects and propagation in optical fibers and components

The power series expansion method was used to solve the wave equation in step-index optical fiber. The cut off frequencies were calculated using 200 coefficients. The cutoff frequencies of TM modes were found to differ from those of TE modes. This difference, which is the error due to the approximations made, was calculated as a function of the relative refractive index difference. A polarization control system was designed to be used in a coherent optical communication system, to restore the state of polarization (SOP) of the light output of a singlemode fiber. Rotating quarter wave and half wave plates were used to compensate for the changes in SOP. The sensitivity of the system was greatly improved by utilizing the heterodyne principle. The effects of neutron irradiation were studied on fiber optic materials (glasses), optical fibers, and photodetectors. In case of the heavy metal fluoride glasses, a red shift was found in the UV edge, which increased with neutron fluence. A very small amount of recovery was observed after three weeks. The shift could be due to the occurrence of color centers on irradiation and/or due to the shift in the Urbach edge itself