One embodiment according to the present invention is a unique system for gas turbine engine control. In some embodiments, first and second openings extend through first and second implant ends, respectively, for permitting a tissue plug to grow through each opening. Desirably, the at least one synthetic sweetener comprises aspartame, acesulfame-K, sucralose, or combinations thereof and the at least one magnesium salt comprises magnesium chloride or magnesium sulfate. Even when a vibration occurs at the corner cube, the reflected light flux is received at the avalanche photodiode as long as the light flux having been reflected at and having exited the corner cube is within the predetermined range.