Growth in the telecommunication industry continues to expand with requirements evolving around increased bandwidth and security. Advances in networking technologies have introduced low cost optical components that has made passive optical networks (PON) the choice for providing huge bandwidth to end users. PON are covered by established standards such as IEEE 802.3ah and ITU-T G.983.1/984.1, with star topology of broadcast and select (B&S) on shared fiber links that poses security vulnerability in terms of confidentiality and privacy;Research and reports in the literature focus around increasing cardinality via coding schemes that lack in addressing security, which was left for implementation in application layers via cryptography. This dissertation presents an approach on security in PON at the network level using slow wavelength hopping techniques and diffusion of data packets among dense wave division multiplex (DWDM). Orthogonal wavelength sequences are generated by mapping an ITU-T G694.1 based wavelength grid matrix and code matrices. The arrangement of wavelengths in the wavelength grid matrix, which can be changed frequently (i.e, hourly) serves as the first key of secure operation. Allocation of generated wavelength sequences distributed in multiple quantities to nodes based on their security level serve as second individual keys for the nodes. In addition, an improved level of security provided via the cycling order of those allocated wavelength sequences to nodes is the third key between the central office (CO) and a node. The proposed approach to PON security provides three new keys available outside the world of cryptography;Various coding techniques are used, and results show that even time spreading/wavelength hopping based on symmetric prime numbers provided the least wavelength sequences; however, it provided excellent correlation properties and level of security. A PON simulation model was implemented to investigate channel impairments in DWDM with 64 channels spaced at 25GHz carried over a 25 km ITU-T G.655 compliant shared fiber cable. Security performance evaluation included analytical studies in classical probabilities to capture the correct order of wavelength hopping sequence using exhaustive searching and reverse construction of matrices from monitored channels. Encouraging results obtained support the feasibility of this proposed technical approach for security.