In the second mode of working, the crystal fibre uses the regular array of holes to influence light in much the same way as the arrangement of atoms in a crystal can determine whether electrons are able to travel easily through it and hence whether the crystal is electrically conducting or not.
Perhaps the most interesting part of this design is its dual-mode power system, which consists of the standard solar cell array as well as a nuclear power source, allowing the rover to operate continuously and in areas that go long periods without sunlight.