Research Of Code And Light Sources In OCDMA-PON

Passive Optical Network (PON) is based on the optical fiber communicationnetwork structure. All devices between the Optical Network Unit (ONU) and OpticalLine Terminal (OLT) are passive optical devices. PON systems reduce the energyconsumption, and they also provide users with a huge transmission bandwidth. Withthe rapid development of the Internet business, access network transmission capacityis under higher requirements. Governments around the world invested heavily inbuilding PON system. Optical fiber to the home (FTTH) has even been achieved insome developed countries in Asia.In the mid-1980s, the CDMA (Code Division Multiple Access) technology wasintroduced into the optical fiber communication system, called Optical CodeDivision Multiple Access (OCDMA) system. It inherits many advantages of CDMA,and it has the following advantages: asynchronous transfer, transparent to differentprotocols, distributed network architecture and easy network management, flexiblenetwork capacity, high information security.Optical Code Division Multiple Access passive optical network (OCDMA-PON)combined OCDMA technology and PON technology. It has the advantages of both,so it is a promising PON technology.Continuously wavelength-tunable light sources are important devices in thePON system. Two tunable light sources are proposed. The proposed tunable lightsources based on a self-seeding RSOA can output the single InternationalTelecommunication Union (ITU) standard wavelength spacing from1529.28nm to1563.6nm. The tunable light sources can also generate multi-wavelengths. Themaximum number of wavelengths generated simultaneously reaches4. Thefrequencies of the generated wavelengths can be selected. They are promising lightsources for the OCDMA-PON, WDM-PON and other hybrid PON, for their advantages of easy management and fast wavelength conversion.Codes are very important to the OCDMA-PON system. It is hard to design acode to improve system performance, the efficiency of resource using and systemsecurity. Codes musat be designed based on the needs of the communication system.Several classical code families used in CDMA and OCDMA are analyzied, and afamily of OCDMA-PON code is proposed. According to the proposed code family,each user is assigned with a unique code. Each user can obtain his own message withthe unique code, and the mutual interference between the different users issuppressed to a very low level. The codes are very easy to obtain. The efficiency ofresource using and system security have been improved at the cost of a worse systemperformance, the error rate is more vulnerable to the impact of system noise.The performance of the OCDMA-PON which uses this new code family isstudied. The impact of noise introduced by the receiver is consideres as the mainnoise. Some conclusions have been obtained.The last chapter is a comprehensive summary.