A Novel Optical Code Division Multiplexing Passive Optical Network Based On Subcarrier Multiplexing

With the rapid development of the Internet, the demand for the network access bandwidth is increasing fast. Due to its high bandwidth advantage characteristic, the optical access technology is becoming the mainstream of the access network. Among various access technologies, the optical code division multiple (OCDM) technology has become a research hotspot because of its prominent advantages such as scalability, low latency access, soft capacity on demand, unique privacy and security. Meanwhile it is considered as one of the promising solutions of the passive optical network.In this paper, through analysis and research of the optical code division multiplexing technology, a novel OCDM-PON system based on subcarrier multiplexing (SCM) technology is proposed by combining the spectral amplitude coding OCDM technology and SCM technology innovatively. The data in this system is mainly processed in the electrical domain, so it belongs to one kind of the electrical-processed OCDM systems (in some other papers it is also referred as the CDM over Fiber systems). Compared with the conventional OCDM systems, the proposed system has many advantage characteristics as follows:1,The proposed system can enable error-free asynchronous transmission with a very simple transmitter and receiver configuration to eliminate beat noise and MAI efficiently where complicated devices for en/decoding, optical thresholding, and time gating are not required.2,The novel system is low-cost and can be integrated easily because the signal procedures are mostly processed in the electrical domain.3,The en/decoders need only operate at the data rate owing to the spatial code spread, high-speed electrical en/decoders that operate at the chip rate are not required. Therefore the requirement for the devices is reduced.4,The truly asynchronous access can be realized to simplify the network protocol and enhance the system flexibility. 5. The proposed system can be integrated with the OFDM an DSP technologies to provide higher spectrum efficiency,larger number of users and higher speed transmission.6,The colorless ONU can be realized to reduce the costs.The main work done in this paper is to introduce and analysis the novel OCDM/SCM system theoretically, and simulate the performance of the downlink and uplink in the system. Besides, a preliminary experiment is carried out. The main contents are outlined as the follows parts:1,The en/decoding scheme of the novel OCDM/SCM-PON system is introduced in detail, and the principle of the cancellation of MUI by using the balanced detection is analyzed theoretically.2,Some of the key system technologies are analyzed, such as the advanced modulation formats and matched filters. Besides, the implementation principles and the dispersion affection of two common subcarrier modulation technologies are discussed, including the double signal band (DSB) modulation and the single signal band (SSB) modulation.3,The implementation principles and methods of the carrier suppression technology and the digital signal processing technology are introduced, and the improvements of the novel system are verified by using them through simulations.4,The VPItransmissionMaker software is used to simulate the uplink and downlink performance of the whole OCDM/SCM-PON system when multi-users transmit simultaneously 60 kilometers. Moreover, the error-free transmission performance and the implementation of the colorless ONU is also analyzed and verified.5,A preliminary experiment of the novel system is carried out.