Remote Measurements of Practical Length Standards Using Optical Fiber Networks and Low-Coherence Interferometers

Practical length standards are remotely measured using a tandem low coherence interferometer through an optical fiber network for communication of about 20 km length between Tsukuba City and Tsuchiura City in Japan. The reference low-coherence interferometer is installed at the National Institute of Advanced Industrial Science and Technology (AIST) and the measurement interferometer with a gauge block of 100 mm nominal length is installed at a calibration laboratory in Tsuchiura City. The optical fibers work as a common path for the tandem interferometric system. Interference fringes are generated when the optical path difference between the reference and measurement interferometers is equal, and thus the gauge block is measured within a standard uncertainty of 46 nm remotely.