  The optical sensors of the IceCube Neutrino Observatory are attached on
vertical strings of cables. They were frozen into the ice in the deployment
holes made by hot water drill. This hole ice, to the best of our knowledge,
consists of a bubbly central column, with the remainder of the re-frozen volume
being optically clear. The bubbly ice often blocks one or several of the
calibration LEDs in every optical sensor and significantly distorts the angular
profile of the calibration light pulses. It also affects the sensors' response
to in-coming photons at different locations and directions. We present our
modeling of the hole ice optical properties as well as optical sensor location
and orientation within the hole ice. The shadowing effects of cable string and
possible optical sensor tilt away from the nominal vertical alignment are also
discussed.
