Fiber-grating-based optical CDMA spectral coding with nearly orthogonal M-sequence codes

An optical spectral coding scheme is proposed for fiber-optic code-division multiple access (FO-CDMA) communications. The spectral coding is based on the pseudo-orthogonality of FO-CDMA codes properly written in the fiber Bragg grating (FBG) devices. An FBG decoder is configured on the basis of orthogonal correlation functions of the nearly orthogonal maximal-length sequence codes. With such a design, an intended receiver user that operates on the defined orthogonal correlation functions will reject interfering users and obtain orthogonality between the FO-CDMA users in the system.