PON Downstream Scheme Supporting Simultaneously Different ONU Categories

We propose a PON downstream scheme simultaneously supporting different categories of ONUs (e.g. different generations), whereby lower-category ONUs employ components with limited bandwidth. Our solution relies upon CDM utilizing Hadamard codes and the spectral properties of its code words. We propose a novel code allocation scheme and provide two optimization approaches by employing an optimized secondary spreading code and a power allocation scheme to improve the system performance.