A fluid separation system is provided for separating a plasma-containing fluid into separated plasma and a concentrated fluid. The system cooperates with a fluid flow circuit including a fluid separation chamber and a plasma outlet line associated therewith for removing separated plasma from the fluid separation chamber. The system includes an optical sensor assembly that receives a portion of the plasma outlet line when the fluid flow circuit has been associated with the fluid separation system. To ensure proper installation of the plasma outlet line, the optical sensor assembly compares light received by its light detector to a baseline value, which is indicative of the amount of light received by the light detector before the plasma outlet line has been installed. The amount of received light being equal to or less than a selected percentage of the baseline value indicates that the plasma outlet line has been properly installed.
