Fiber optics deliver laser light directly to the measurement axes, eliminating the need for multiple remote beam splitters, benders, and adjustable mounts. The RLE20 is suitable for X-Y positioning systems that require precision control over two axes from a single laser source. The interferometer system and components provide subnanometer nonlinearity and resolution of 38 pm. The system provides positional output signals in differential digital RS-422 and/or 1-Vpp sine/cosine formats and digital outputsignal resolution up to 10 nm.