Tunable fiber Bragg grating-based a pair of m-sequence coding for optical CDMA

A fiber-optical code-division multiple-access (FO-CDMA) scheme, which is based on spectral coding, is proposed. The spectral coding is based on the pseudo-orthogonality of FO-CDMA codes properly written in the fiber Bragg grating (FBG) devices. A pair of maximal-length sequence codes is used to exemplify the coding and correlation processing among FO-CDMA user codes. Cooperating with TDMA and the tunable FBG coding devices, it can support more users without mass-deploying coding devices. Instead of making a direct correlation operation, we configure an FBG decoder scheme on the basis of orthogonal correlation functions of nearly orthogonal m-sequence codes. With the devised FBG decoder architecture, an intended receiver user that operates on the defined orthogonal correlation functions will reject any interfering user and obtain a complete orthogonality between the FO-CDMA users in the system. We also show that this devised system can provide a simple error detecting function.