In one embodiment, a system comprises an enclosure, at least one item enclosed within the enclosure, and at least one optical medium disposed between the enclosure and the at least one item. The at least one optical medium is arranged in a pattern such that the at least one optical medium substantially encloses the at least one item. The system further comprises a generator communicatively coupled to a first portion of the optical medium. The generator generates a pseudo-random sequence of bits. The pseudo-random sequence of bits is optically transmitted over the optical medium. The system further comprises a detector communicatively coupled to a second portion of the optical medium. The detector detects any portion of the pseudo-random sequence of bits received at the second portion of the optical medium.