HIGH-RESOLUTION DISTANCE METER USING OPTICAL MODULATORS AT 3.5 GHZ

A high-resolution distance meter is fabricated using optical waveguide modulators. The modulation frequencies of the optical modulators are around 3.5 GHz, while the modulation frequencies of the optical intens ity are around 7 GHz because the modulation bias voltages are set at t he peaks of the electrooptic characteristics. The distance meter was e valuated in the National Research Laboratory of Metrology (NRLM) tunne l, which is a semiunderground tunnel, The measurement resolution has a standard deviation of 12 mu m for a distance range of 0.5 to 5 m afte r correction of the cyclic error. (C) 1997 Society of Photo-Optical in strumentation Engineers.