Polarization maintaining patch cords are built with polarization maintaining panda fiber and connectors like FC, SC, and LC. They feature low insertion loss, high extinction ratio, and high return loss. The slow or fast axis of the fiber can be aligned to the connector key. Specifications include insertion loss less than 0.5dB, optical return loss of 50-60dB, and extinction ratio greater than 23dB. They use PM panda fiber and can operate from -40 to 80 degrees Celsius.