Well the RLG is easy if you can understand the regular gyro INS. Basically you have one laser ring for each dimension ( as I think the conventional system has one gyro for each dimension). Basically you point a laser in each direction around the glass triangle and measure how long each beam of light takes to get back to the start. If you rotate the triangle about its plane then one receiver will move closer to its light source, and the other receiver will move further away from it's light source. This creates a difference in the time it takes each laser to travel the circuit, which is manifested in an apparent frequency change of the laser light. By some clever maths you can thus determine how much the triangle has rotated by and then do all the usual calculations to determine aircraft position.