The PolaStay™ polarization stabilizer actively maintains a stable output state of polarization (SOP) against rapid input SOP fluctuations as fast as 2 ms, and tracks against an endlessly rotating input SOP up to 16p/s without reset. This unique product is a complete system consisting of General Photonics’ polarization controller, in-line polarization monitor, and proprietary algorithm. The instrument's output can be either single mode fiber or PM fiber with the output polarization aligned to its slow axis. When a polarizer is placed at the output, the maximum power fluctuation caused by input polarization fluctuation is less than 0.1 dB. This instrument can be used to suppress noise figure in optical amplifiers, reduce PDL effects, demultiplex polarization division multiplexed channels, and eliminate polarization fading in coherent communication and fiber sensor systems. In addition to the standard configuration, specialized versions are available for low power applications (down to -30 dBm) and special wavelengths (1064 nm).