A fiber optic laser encoder system introduced by Renishaw Inc. offers picometer resolution, differential measurement and parts-per-billion laser frequency stability. The RLE20 uses fiber optics to deliver the laser light directly to the measurement axes, eliminating the need for remote beamsplitters, benders and adjustable mounts. The interferometer system and components achieve subnanometer nonlinearity and 38-pm resolution. The laser is connected to the detector head by a 3-m fiber optic cable. Positional output signals are provided in differential digital RS-422 and/or 1 Vpp sine/cosine formats.