Shun-er Chen

Study and implementation using FPGA of RTT in EPON

Nowadays, EPON technology is regarded as one of the best candidate technology for next generation broadband access technology. In this paper, the architecture of EPON is introduced first. The upstream in EPON adopts TDMA/TDM technology, and it is necessary to know the exact RTT(Round Trip Time), the principle of RTT measurement (ranging) and RTT compensation are introduced. We use Xilinx FPGA SpartanII chip series to realize ranging function module, the main idea of implementation is given in this paper, and this can be used for further study of hardware implementation.

Research and optimization of FBG apodization technic based on Double-exposure method

The reflection spectral influence of fiber Bragg gratings (FBG) caused by refractive index of DC component was analyzed. FBG with double exposure apodized by raised cosine beam, was found the best way to eliminate reflection sidelobe among three beams (raised-cosine, Gaussian and cosine beam).Through adjusting Full Width Half Maximum (FWHM) parameter in the best double-exposure apodising function, the optimal apodising function was obtained with its sidelobe suppression value 35dB.

Implementation of LAN emulation in EPON

The point-to-point LAN emulation and shared LAN emulation over EPON solution are introduced. Two different kinds of LAN function are placed in a single model named IULSLE upper MAC layer to simplify the design, whose functions like a bridge and can be attached to any device, whether a bridge, a router, or a host computer. A Logical Link is established between OLT and ONU which is identified with a LLID attaching MAC address. In this model, the function of RS sublayer is only processing LLIDs according by the MAC ADD and LLID table in IULSLE module, and MAC layer is as normal bridge. The main LAN emulating function is accomplished by IULSLE block making OLT operates as a bridge. Not only the hardware block diagram but also the actually circuit are accompanied in detail.

Double muxed/demuxed CWDM multiservice transmission system used in metro-networks

A CWDM multi-service transmission system used in metro-networks is proposed and demonstrated. In the system, two wavelengths, with channel spacing of about 5 nm and 6 nm in old band and C band, respectively, are multiplexed by using fiber tapered couplers, instead of using thin film filter couplers. The two multiplexed bands are doubly multiplexed in a fiber. The system is designed to transmit different kinds of signals including E1, IP, E3/T3 and etc in metro networks. So the system can be used to transmit four different kinds of network service in one fiber link. The designs of the whole system and the related subsystems are described in details, and the corresponding tested results are also given.

A novel design of optical CDMA system based on TCM and FFH

For the application in Passive Optical Network (PON), a novel design of OCDMA system scheme is proposed in this paper. There are two key components included in this scheme: a new kind of OCDMA encoder/decoder system based on TCM and FFH and an improved Optical Line Terminal (OLT) receiving system with improved anti-interference performance by the use of Long Period Fiber Grating (LPFG). In the encoder/decoder system, Trellis Coded Modulation (TCM) encoder is applied in front of the FFH modulator. Original signal firstly is encoded through TCM encoder, and then the redundant code out of the TCM encoder will be mapped into one of the FFH modulation signal subsets for transmission. On the receiver (decoder) side, transmitting signal is demodulated through FFH and decoded by trellis decoder. Owing to the fact that high coding gain can be acquired by TCM without adding transmitting band and reducing transmitting speed, TCM is utilized to ameliorate bit error performance and reduce multi-user interference. In the OLT receiving system, EDFA and LPFG are placed in front of decoder to get excellent gain flatness on a large bandwidth, and Optical Hard Limiter (OHL) is also deployed to improve detection performance, through which the anti-interference performance of receiving system can be greatly enhanced. At the same time, some software is used to simulate the system performance for further analysis and authentication. The related work in this paper provides a valuable reference to the research.

Studies of OAM sublayer in EPON and related FPGA implementation

Ethernet Passive Optical Network (EPON) must be equipped with Operations, Administration and Maintenance(OAM) features. Functions of 802.3ah OAM protocol in EPON system are Link performance monitoring, Fault detection and Fault signaling, Loopback testing. The related five types of OAMPDUs are Variable Request/Response, Information, Event Notification, Loopback Control and Organization Specific. Both OAM functions and OAMPDUs described in detail. The main functions provided by OAM are partitioned into three components: multiplexer, parser and client and control. As a part of our EPON system, the OAM sublayer components has been implemented using FPGA which can manage high speed Non-OAMPDUs and slow protocol at the same time. The OAM sublayer module and implemented its function are designed by using Xilinx PPGA. Not only the hardware block diagram but also the actually circuit are accompanied in detail. The result indicates that the data is the same as the protocol description.

Design and realization of high-stability digital temperature controller in LD

A reference model is setup for a high stability temperature controlling in LD by testing the response characteristics of LD refrigerator, and an SoC based digital temperature controller is designed and realized, which is simple in hardware, and flexible in software. Experiment results demonstrate that the temperature drift of LD is within ±0.05 °C.

Application of SNMP on CATV

A new type of CATV network management system developed by universal MCU, which supports SNMP, is proposed in this paper. From the point of view in both hardware and software, the function and method of every modules inside the system, which include communications in the physical layer, protocol process, data process, and etc, are analyzed. In our design, the management system takes IP MAN as data transmission channel and every controlled object in the management structure has a SNMP agent. In the SNMP agent developed, there are four function modules, including physical layer communication module, protocol process module, internal data process module and MIB management module. In the paper, the structure and function of every module are designed and demonstrated while the related hardware circuit, software flow as well as the experimental results are tested. Furthermore, by introducing RTOS into the software programming, the universal MCU procedure can conducts such multi-thread management as fast Ethernet controller driving, TCP/IP process, serial port signal monitoring and so on, which greatly improves efficiency of CPU.

Supervisory system based on subcarrier overmodulation for optical amplifier system

We have reviewed some techniques which are used in supervision of EDFAs so far. Based on these techniques, we propose a new supervisory scheme and discuss some key problems in the scheme. This kind of SV system will be quite important for the all-optical networks in the future.

Free-space optics: last-mile alternative

The present status of the use of fiber-free optics technology for solutions providing high speed local access connectivity is introduced. The advantages of the technologies are presented. By analyzing the factors that limit the public application of the free-space optics, an integrated network solution that combines the benefits of both microwave technology and free-space technology is presented.