Roy Greason wrote: > What is a fibre optic loop - Just interested. Roy: In this context, it's a gyroscope. The usual name for it is "Ring Laser Gyro". It works by splitting a laser beam into two beams, each of which travels through a fiber optic loop... The beams follow the same path, but in opposite directions. The beams are combined after their trip around the loop. If the gyro isn't rotating, each beam will have traveled the same distance and they'll still be in phase at the output detector. If the gyro IS rotating, the beams will have traveled DIFFERNT distances and they'll be out of phase when they're recombined. Since the amplitude of the output signal is related to the degree of phase shift, and since the phase shift is related to the rotation rate, you can calculate rotation rate by carefully measuring the amplitude of the output signal. The primary advantage of laser gyros over mechanical gyros is that lasers don't drift over time... This makes them suitable for use in aircraft, etc. For high-precision applications where the total flight time is relatively short (like, for instance, guiding intercontinental ballistic missiles), laser gyros are generally NOT used... Mechanical gyros are preferred because they're more accurate. At least, they WERE preferred; I don't know whether any recent advances have been made in laser-gyro technology. -Andy === Andrew Warren - fastfwd@ix.netcom.com === === Fast Forward Engineering - Vista, California === === === === Custodian of the PICLIST Fund -- For more info, see: === === http://www.geocities.com/SiliconValley/2499/fund.html ===