Design and Analysis of a Fiber Optical Code-Division multiple-Access System with Pseudo-Orthogonal Coded Fiber Bragg Gratings

• Main Authors: Dar-Zu Hsu, 徐達儒
• Other Authors: Jen-Fa Huang
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/42525247037625472587

碩士 === 國立成功大學 === 電機工程學系 === 88 === Asynchronous Transfer Mode (ATM) technology is currently being used to implement the Broadband Integrated Services Digital Network（B-ISDN）. Fiber-Optic Code-Division Multiple-Access (FO-CDMA) is the most suitable selection for multiple accessing. FO-CDMA proposed by this paper can achieve the exchange of users' data in ATM switchers and the routing in the network. An optical spectral coding scheme is devised for fiber-optic code-division multiple-access (FO-CDMA) networks. The spectral coding is based on the pseudo-orthogonality of FO-CDMA codes properly written in the fiber Bragg grating (FBG) devices. For an incoming broadband optical signal having spectral components equal to the designed Bragg wavelengths of the FBG, the spectral components will be reflected and spectrally coded with the written FO-CDMA address codes. Each spectral chip has different central wavelength and is distributed over the spectrum of the incoming light source. Maximal-length sequence codes (m-sequence codes) are chosen as the signature or address codes to exemplify the coding and correlation processes in the FO-CDMA system. By assigning the N cycle shifts of a signal m-sequence code to N users, we get an FO-CDMA network that can support N simultaneous users. The M-sequences provide higher system capacity than unipolar codes. Under the proper design, the new typical optical CDMA system can improve the lack of system capacity of using unipolar codes. To overcome the limiting factor of multiple-access interference (MAI) on the performance of the FO-CDMA network, an FBG decoder is configured on the basis of orthogonal correlation functions of the adopted pseudo-orthogonal codes. An intended receiver user that operates on the defined orthogonal correlation functions will reject interfering user and obtain complete orthogonality between the FO-CDMA users in the network.