Abstract: Fiber optic communication uses several multiple access schemes. Among them Optical Code Division Multiple Access (OCDMA) is one of the multiple access schemes that are widely used because of their advantages such as the flexibility in the allocation of channels, ability to operate asynchronously, enhanced privacy and increased in burst networks. This paper deals with the security enhancement of an OCDMA system. Network security has three major security goals: confidentiality, availability and message integration between senders and receivers. To overcome the drawback of existing OCDMA system cryptography is applied. Cryptography can be used by everyone to protect the confidentiality of their information transmitted over insecure channels as well as to provide privacy, authenticity and data integrity. To provide more confidentiality two cryptographic techniques are incorporated into the system. The proposed technique is based on cryptography which includes the encryption and decryption of the information with the employment of a random key. This paper also discusses the comparison of the above two cryptographic techniques in the OCDMA system to find the best suited encryption technique for OCDMA system that provides strong security.

Keywords: Optical Code Division Multiple Access, Spreading codes, Cryptography, Advanced Encryption Standard, Blowfish.