Rare-Earth Iron Garnets for Fiber Optic Current Sensors

Fiber optic current sensors with temperature-independent sensitivity have been developed. For Faraday rotators of the sensors, highly Bi-substituted rare-earth iron garnets, BixGdYY3-(X+Y) Fe5O12, are prepared by a liquid phase epitaxy (LPE) method. It is found that the temperature dependence of the sensitivity constants is improved by Gd substitution. The crystal with the components of X=1.3 and Y=0.43 is found to show the least temperature variation of the sensitivity constants within ±0.5% between 253 and 353K. The sensor modules using the crystals have good characteristics in practical use. The sensor units for monitoring the condition of power distribution lines have high environmental durability, high insulation, and no electromagnetic induction.