Hongbin Huang

Dynamitic cascaded FBG based filter used in DWDM networks

The characteristics of uniform fiber Bragg gratings (FBGs) is analyzed. The reflected spectra in apodized uniformly periodic FBGs are calculated and the double exposure technique is used in suppressing the sidelobes of uniform gratings. After that, the corresponding FBGs filters used in DWDM networks and systems are imprinted. Based on the apodized FBGs, a cascaded FBGs filter module is proposed, in which two, or more, pieces of identical FBGs, with the same central wavelength, same bandwidth and same reflectivity, are spliced in series and each FBG is equipped with tuning device. By controlling the tuning device, the module can act either as a tunable single channel filter with its central wavelength and/or bandwidth being tunable, or as a double channel filter with its central wavelength being tunable. The tested results demonstrated that the module can dynamically tuned in the range of several nanometers.

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.

Design and implementation of programmble semiconductor pulse seed laser used in MOPA

A programmable semiconductor pulse seed laser, with a maximum peak current of 20A, repetition frequency from 10Hz to 1MHz and pulse width from 16ns to 1µs, was designed and implemented for MOPA pulsed fiber laser. The repetition frequency and pulse width can be continuously adjusted via DDS technique in FPGA.

Design and implementation of distributed high power LD driver used in fiber laser

In high power fiber laser, plenty of LDs are required as pumping source in order to get efficient high power output. It is obvious that the way to drive those LDs, effectively, simultaneously and reasonably, is a key factor in achieving excellent fiber laser. In this paper, a novel design of the so-called “distributed-driving” is proposed, where quite amount of LDs are independently driven and controlled in several separated channels which are dominated with one MCU. Besides, in order to ensure the stability of the current and temperature in those LDs, related protection measures based on effective control algorithm are taken while a perfect air circulation system to prevent the LDs from the temperature effects, is designed. The driving system is demonstrated through the corresponding test results, which show that the driving current can be up to 10A, with a high stability, whose fluctuation is less than 1% /h.

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.