Some 20-regular CDP(5,1;20u) and their applications

We give a direct construction for 20-regular cyclic difference packings CDP(5,1;20p)ʼs when is a prime. Then, recursively, we prove the existence of an optimal (20⋅α3u,5,1) optical orthogonal code for every nonnegative integer α and any positive integer u whose prime factors are all congruent to 1 (mod 6).