High Speed Optical Links Using CAP Modulation and Novel Equalisation Techniques

High speed optical links suffer from inter-symbol-interference (ISI) due to their limited bandwidth. Equalisation is typically used to mitigate ISI and therefore improve the link capacity. This dissertation explores novel equalisation techniques for carrierless amplitude and phase (CAP) modulation based optical communication systems including OM4 based and plastic optical fibre (POF) based links. An 850 nm VCSEL based OM4 link using CAP-16 scheme is studied. For the first time, the CAP equaliser, is proposed to mitigate both crosstalk channel interference (CCI) and ISI in the link at the receiver side. Performance comparisons are studied between the CAP-16 scheme using CAP equaliser and a conventional equaliser, pulse amplitude modulation (PAM-4) scheme, and discrete multitone (DMT) scheme. CAP based data transmission of 112 Gb/s is achieved over 150 m OM4 fibre with this novel equaliser, while the conventional equaliser can only support over 1 m OM4 fibre and fails to recover the signals at the same data rate. In addition, this novel equaliser provides a 1.2 dB and 1.7 dB improvement in receiver sensitivity over PAM-4 and DMT schemes, respectively, at 112 Gb/s over 100 m OM4 fibre. A novel pre-CAP-equaliser solving CCI at the transmitter side is also proposed. Data transmission of 56 Gb/s over 100 m OM4 fibre is reported experimentally with an improvement of 0.7 dB in receiver sensitivity compared to using the CAP equaliser at the receiver side. A simulation study shows a 2 dB improvement in receiver sensitivity at 112 Gb/s over 100 m OM4 fibre. Furthermore, an artificial neural network (ANN) equaliser in conjunction with the CAP equaliser structure is explored in a VCSEL based OM4 fibre link in order to further mitigate the nonlinear impairments. For 112 Gb/s data transmission over 100 m OM4 fibre, a 2.4 dB improvement of receiver sensitivity is achieved compared to the CAP equaliser. In addition to the electrical equalisers, a monolithically integrated silicon optical equaliser consisting of three taps is used for 50 Gb/s data transmission. After 10 km standard single mode fibre (SSMF), error free eye diagrams at the receiver are demonstrated. A μLED based POF link based on an APD receiver is also investigated with the CAP equaliser at the receiver side. Data transmission rates of 4 Gb/s over 25 m and 5 Gb/s over 10 m POF links are demonstrated with this equaliser while the conventional equaliser can only support 4 Gb/s over 10 m and fails to recover the signals for 5 Gb/s data transmission

Transmission capacity improvement for high speed multimode waveguide links using advanced optical launch and multilevel modulation schemes

This dissertation investigates the potential technologies in both optical and electrical domains for transmission capacity improvement in multimode waveguide links. The first half of the dissertation focuses on the multimode waveguide made from glass, the multimode glass fibre. A new optical launch scheme is developed, namely low-loss Hermite-Gaussian launch, to achieve single mode group excitation in the multimode glass fibre. Novel implementations using elliptical Gaussian beam and square-shaped launching profiles are developed, achieving a coupling loss at least 2.5 dB lower than the previously reported line launch scheme. Theoretical calculations show that these launches provide 50% bandwidth-distance product improvement over the dual launch scheme for a 99% yield of the entire OM1 fibre installed base. It is also found experimentally that the low-loss Hermite-Gaussian launches outperform dual launch for fibres favouring either centre launch or offset launch. Misalignment tolerance measurements reveal that the bandwidth improvements over a perfectly aligned centre launch using these launches are maintained within a radial offset range of ≤ 8 μm. Error free transmissions at 10 Gbit/s are demonstrated for different orders of low-loss Hermite-Gaussian launches over 250 m worst case OM1 fibre without the use of equalisation. The second half of the dissertation concentrates on another type of multimode waveguide which is made from plastic, namely step-index plastic optical fibre (SI-POF). Both baseband and passband multilevel modulation schemes are investigated to provide over gigabit/s transmissions using LEDs. For the first time, fractionally-spaced equalisers are thoroughly examined in multilevel modulation systems for LED-based SI-POF links. Based on the link budget analysis, it is found that PAM-8 and CAP-64 are the best baseband and passband solutions respectively. For 25 m links, calculations show that PAM-8 and CAP-64 can achieve data rate up to 3 Gbit/s with system margins of 2.2 dB and 1.3 dB. Meanwhile for 50 m links, they achieve data rate up to 1.5 Gbit/s with system margins of 1.9 dB and 1.2 dB respectively. A new FPGA system is developed to experimentally evaluate the PAM-8 and CAP-64 schemes. Error free transmissions are achieved at 3 Gbit/s using PAM-8 for 25 m SI-POF and 1.5 Gbit/s using CAP-64 for 50 m SI-POF. These results record the highest bit-rate-distance-product achieved in LED-based SI-POF links without the use of forward error correction

[[alternative]]System Evaluation, Simulation Platform Set Up and Baseband Circuit Implementation for Wireless Sensor Network

計畫編號：NSC93-2213-E032-023研究期間：200408~200507研究經費：515,000[[abstract]]本計畫分三年以實現無線感測網路之系統評估模擬平台建置與基頻電路研製。本計劃研 究子題如下： (A) IEEE 802.15.4 系統之分析及設計 1. 媒介擷取控制層與實體層間之介面設計 2. 系統架構的確定，系統規格及各子方塊之間之介面規格之訂定 3. 低功率基頻電路的設計及探討 4. 接收機技術研究(同步、通道等化、信號偵測等) 5. 利用 ADS 與 Matlab 以建立模擬平台 6. 傳送端與接收端低功率基頻電路之硬體實現 (B) IEEE 802.15.4a 系統之分析及設計 1. UWB 基本原理之研究與探討 2. UWB 傳送與接收基本技術之研究 3. 利用 ADS 及 Matlab 建立模擬平台，對 UWB 之架構模擬 4. UWB 基本方塊規格之訂定 5. 精確定位之研究 (C) IEEE 802.15.4 之MIMO 架構設計 1. MIMO 架構之演算法與架構之研究 2. MIMO 架構之用於IEEE 802.15.4 之通道效應之探討與研究 3. 利用MIMO 架構傳送MPEG-4 之效能探討 4. MIMO 架構之接收技術之研究 5. 利用 ADS 及 Matlab 建立性模擬平台以研究多頻帶的傳輸特性 6. 探討如何利用基頻電路的切換以達低功率而高速的信號傳送 (D) 通道分析及模型的建立 1. 通道傳送損失特性之分析 2. 路徑衰減及多重路徑之分析 3. 路徑衰減之經驗公式推導 4. 通道模型之建立 5. 通道等化器演算法之推導及分析(E) 模擬平台的建立 1. 利用 ADS 程式以建立基頻及 RF 端之模擬平台 2. 利用 Matlab 程式以建立基頻及 RF 端之模擬平台 3. 基頻及 RF 端 ADS 模擬平台的介面設計 4. 基頻及 RF 端 Matlab 模擬平台的介面設計 5. 系統特性的模擬及數據分析 (F) 測試平台的建立 1. IEEE 802.15.4 實體層各子方塊之 Verilog 程式燒錄至 FPGA 並測試 2. IEEE 802.15.4 實體層整合電路之 Verilog 程式燒錄至 FPGA 並測試 3. Mulit-Band 實體層之 Verilog 程式燒錄至 FPGA 並測試 4. IEEE 802.15.4 實體層 ASIC 之測試 5. IEEE 802.15.4 實體層 ASIC 與 RF 之整合測試 6. IEEE 802.15.4 實體層 ASIC 與 MAC 之整合測試 7. IEEE 802.15.4 實體層 ASIC , MAC 及 RF 之整合測試[[sponsorship]]行政院國家科學委員

On Coding and Detection Techniques for Two-Dimensional Magnetic Recording

Edited version embargoed until 15.04.2020 Full version: Access restricted permanently due to 3rd party copyright restrictions. Restriction set on 15/04/2019 by AS, Doctoral CollegeThe areal density growth of magnetic recording systems is fast approaching the superparamagnetic limit for conventional magnetic disks. This is due to the increasing demand for high data storage capacity. Two-dimensional Magnetic Recording (TDMR) is a new technology aimed at increasing the areal density of magnetic recording systems beyond the limit of current disk technology using conventional disk media. However, it relies on advanced coding and signal processing techniques to achieve areal density gains. Current state of the art signal processing for TDMR channel employed iterative decoding with Low Density Parity Check (LDPC) codes, coupled with 2D equalisers and full 2D Maximum Likelihood (ML) detectors. The shortcoming of these algorithms is their computation complexity especially with regards to the ML detectors which is exponential with respect to the number of bits involved. Therefore, robust low-complexity coding, equalisation and detection algorithms are crucial for successful future deployment of the TDMR scheme. This present work is aimed at finding efficient and low-complexity coding, equalisation, detection and decoding techniques for improving the performance of TDMR channel and magnetic recording channel in general. A forward error correction (FEC) scheme of two concatenated single parity bit systems along track separated by an interleaver has been presented for channel with perpendicular magnetic recording (PMR) media. Joint detection decoding algorithm using constrained MAP detector for simultaneous detection and decoding of data with single parity bit system has been proposed. It is shown that using the proposed FEC scheme with the constrained MAP detector/decoder can achieve a gain of up to 3dB over un-coded MAP decoder for 1D interference channel. A further gain of 1.5 dB was achieved by concatenating two interleavers with extra parity bit when data density along track is high. The use of single bit parity code as a run length limited code as well as an error correction code is demonstrated to simplify detection complexity and improve system performance. A low-complexity 2D detection technique for TDMR system with Shingled Magnetic Recording Media (SMR) was also proposed. The technique used the concatenation of 2D MAP detector along track with regular MAP detector across tracks to reduce the complexity order of using full 2D detection from exponential to linear. It is shown that using this technique can improve track density with limited complexity. Two methods of FEC for TDMR channel using two single parity bit systems have been discussed. One using two concatenated single parity bits along track only, separated by a Dithered Relative Prime (DRP) interleaver and the other use the single parity bits in both directions without the DRP interleaver. Consequent to the FEC coding on the channel, a 2D multi-track MAP joint detector decoder has been proposed for simultaneous detection and decoding of the coded single parity bit data. A gain of up to 5dB was achieved using the FEC scheme with the 2D multi-track MAP joint detector decoder over un-coded 2D multi-track MAP detector in TDMR channel. In a situation with high density in both directions, it is shown that FEC coding using two concatenated single parity bits along track separated by DRP interleaver performed better than when the single parity bits are used in both directions without the DRP interleaver.9mobile Nigeri

Overcoming degradation in spatial multiplexing systems with stochastic nonlinear impairments

Single-mode optical fibres now underpin telecommunication systems and have allowed continuous increases in traffic volume and bandwidth demand whilst simultaneously reducing cost- and energy-per-bit over the last 40 years. However, it is now recognised that such systems are rapidly approaching the limits imposed by the nonlinear Kerr effect. To address this, recent research has been carried out into mitigating Kerr nonlinearities to increase the nonlinear threshold and into spatial multiplexing to offer additional spatial pathways. However, given the complexity associated with nonlinear transmission in spatial multiplexed systems subject to random inter-spatial-path nonlinearities it is widely believed that these technologies are mutually exclusive. By investigating the linear and nonlinear crosstalk in few-mode fibres based optical communications, we numerically demonstrate, for the first time, that even in the presence of significant random mixing of signals, substantial performance benefits are possible. To achieve this, the impact of linear mixing on the Kerr nonlinearities should be taken into account using different compensation strategies for different linear mixing regimes. For the optical communication systems studied, we demonstrate that the performance may be more than doubled with the appropriate selection of compensation method for fibre characteristics which match those presented in the literature