A novel code-shift-keying scheme against upstream eavesdropping in optical code division multiple access network

A 4-code code switching keying (CSK) modulation scheme was proposed. It can scramble the optical codes (OC) bit by bit to defeat the differential eavesdropping toward the upstream of the optical code division multiple access (OCDMA) network. The transmission and security test results for the 4-code CSK-OCDMA system at a data rate of 2.5 Gb/s were presented in this paper. It verified that the CSK-OCDMA system can provide a security and error free transmission service in an access network. The proposed system has a simple framework, enhanced security and especially asynchronous transmission compared to other CSK-OCDMA systems against eavesdropping.