Role of laser linewidth in high speed DWDM system by incorporating duobinary modulation scheme

This work is focused on realization of DWDM system of 1.6 Tb/s ultra high capacity using duobinary return to zero modulation scheme with EDFA and dispersion compensation scheme.Duo binary format is used as it is suitable for high spectral efficiency at large transmission distance.40 channels having capacity of 40 Gbps data rate each are multiplexed with channel spacing of 100 GHz to realize 1.6 Tbps as total transmission over optical span of 60 Km by using pre and post compensation technique.The comparison of parameters is observed in terms of Q value and eye opening keeping BER in acceptable range Moreover, the role of laser line-width is also investigated to minimize the non linearity and four wave mixing effect

Towards Higher Speed Next Generation Passive Optical Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen

Directly Phase Modulated Transmitters and Coherent Recivers for Future Passive Optical Networks (PON)

En los últimos años, el tráfico de dato transmitido en las redes ópticas de acceso ha crecido exponencialmente debido a nuevos servicios como pueden ser la computación en la nube, el video online, la realidad virtual y aumentada, el internet de las cosas (IoT) y la convergencia entre las redes ópticas y redes inalámbricas en el paradigma del 5G. Estos nuevos servicios endurecen los requerimientos de las redes ópticas de acceso, como pueden ser unas tasas de datos más altas, un mayor alcance y un mayor número de usuarios. Para abordar estos requerimientos, esta tesis ha investigado, desarrollado y analizado nuevas tecnologías para transmisores y receptores orientadas a los dos tipos de redes ópticas de acceso que la comunidad científica ha identificado como posibles candidatas. Estos dos tipos de redes ópticas son las redes uDWDM y las redes TWDM como las redes NG-PON2 y sus evoluciones.Las redes uDWDM están basadas en la transmisión de tasas de datos relativamente bajas, por debajo de 2.5 Gbps, que son dedicadas en su totalidad a los usuarios finales. Estas tasas de datos relativamente bajas son multiplexadas en longitud de onda usando intervalos frecuenciales estrechos, del orden de 12.5 GHz o 6.25 GHz. En esta tesis, los transmisores modulados directamente en fase se han propuesto como posibles candidatos para estas redes uDWDM. En concreto, se han propuesto un DFB modulado directamente en fase con una tasa de datos de 1 Gbps; un RSOA bombeado por un VCSEL y modulado directamente en fase con una tasa de datos de 1 Gbps; y un VCSEL modulado directamente en fase con una tasa de datos de 1.25 Gbps y 2.5 Gbps. Estas señales moduladas directamente en fase son recibidas con un receptor heterodino con un único fotodiodo (PD) para mantener el coste tan bajo como sea posible. La combinación de estos transmisores modulados directamente en fase con el receptor heterodino con un único PD ha sido probada como unos candidatos muy prometedores para las redes ópticas de acceso basadas en redes uDWDM. Estas combinaciones proveen sensibilidades que varían entre -39.5 dBm y -52 dBm, que se traducen en balances de potencia que van desde 38.5 dB a 51 dB y por lo tanto en ratios de división o número de usuarios de entre 128 y 1024 después de una transmisión de 50 km a través de fibra monomodo estándar (SSMF).Además, los links de 1 Gbps formados por la modulación directa de DFBs o de RSOAs bombeados por VCSELs y el receptor heterodino con un único PD son usados como enlace de subida en canales bidireccionales. Estos enlaces de subida son combinados con enlaces de bajada basados en Nyquist-DPSK generada con un MZM y recibidos con un receptor heterodino de un único PD. Como parte de análisis de los canales bidireccionales, se ha analizado el estudio de la viabilidad del uso de LOs de bajo coste, como DFBs o VCSELs, en los receptores heterodinos con un único PD. Estos canales bidireccionales son también unos candidatos prometedores para las futuras redes uDWDM, ya que en esta tesis se ha probado que pueden proveer enlaces full-duplex de 1 Gbps usando intervalos frecuenciales tan pequeños como 6.25 GHz o 5 GHz. Estos canales bidireccionales tienen balances de potencia que van desde 37 dB a 42 dB y tienen posibles ratios de división de 128 o 256 después de una transmisión de 50 km a través de SSMF.Esta tesis también ha investigado y desarrollado receptores quasicoherentes para redes NG-PON2 y sus evoluciones. Este tipo de redes están basadas en altas tasas de datos, como 10 Gbps para redes NG-PON2 y 25 Gbps para las futuras evoluciones de NG-PON2, en entornos multi longitud de onda donde los usuarios son multiplexados en tiempo y longitud de onda (TWDM). El receptor quasicoherente usa la amplificación coherente gracias a la recepción heterodina y por tanto la sensibilidad del receptor es mejorada en comparación con los esquemas de detección directa. El receptor quasicoherente es independiente a la polarización, lo cual es una característica importante para los receptores coherentes. Además, el receptor quasicoherente permite seleccionar el canal de trabajo sin la necesidad de filtros ópticos y es un receptor independiente de la longitud de onda debido a que el canal de trabajo se puede elegir ajustando la longitud de onda del LO. El receptor quasicoherente de 10 Gbps muestra una sensibilidad -35.2 dBm y por tanto permite un balance de potencias de 35.64 dB y un ratio de división de 128 después de una transmisión de 40 km a través de SSMF.La combinación del receptor quasicoherente con un ecualizador FFE/DFE permite combatir la dispersión cromática de la banda C y conseguir un link de 25 Gbps con un alcance de 20 km a través de SSMF. El receptor quasicoherente a 25 Gbps con ecualización FFE/DFE muestra una mejor sensibilidad de -30.5 dBm con el llamado ecualizador de altas prestaciones, lo que lleva a un balance de potencias de25 dB. Si se utilizada el llamado ecualizador de baja complejidad, la sensibilidad cae a -27 dBm y el balance de potencias cae a 23 dBm. En ambos casos, el receptor quasicoherente a 25 Gbps con ecualización FFE/DFE permite un ratio de división de 32 después de una transmisión de 20 km a través de SSMF.En conclusión, esta tesis ha presentado transmisores (DFB, RSOA y VCSEL) modulados directamente en fase combinados con un receptor heterodino con un único PD como potenciales candidatos para las redes uDWDM. Esta tesis también ha presentados los receptores quasicoherentes como unos candidatos muy prometedores para las redes NG-PON2 y sus futuras evoluciones.<br /

Design Techniques for High Performance Serial Link Transceivers

Increasing data rates over electrical channels with significant frequency-dependent loss is difficult due to excessive inter-symbol interference (ISI). In order to achieve sufficient link margins at high rates, I/O system designers implement equalization in the transmitters and are motivated to consider more spectrally-efficient modulation formats relative to the common PAM-2 scheme, such as PAM-4 and duobinary. The first work, reviews when to consider PAM-4 and duobinary formats, as the modulation scheme which yields the highest system margins at a given data rate is a function of the channel loss profile, and presents a 20Gb/s triple-mode transmitter capable of efficiently implementing these three modulation schemes and three-tap feedforward equalization. A statistical link modeling tool, which models ISI, crosstalk, random noise, and timing jitter, is developed to compare the three common modulation formats operating on electrical backplane channel models. In order to improve duobinary modulation efficiency, a low-power quarter-rate duobinary precoder circuit is proposed which provides significant timing margin improvement relative to full-rate precoders. Also as serial I/O data rates scale above 10 Gb/s, crosstalk between neighboring channels degrades system bit-error rate (BER) performance. The next work presents receive-side circuitry which merges the cancellation of both near-end and far-end crosstalk (NEXT/FEXT) and can automatically adapt to different channel environments and variations in process, voltage, and temperature. NEXT cancellation is realized with a novel 3-tap FIR filter which combines two traditional FIR filter taps and a continuous-time band-pass filter IIR tap for efficient crosstalk cancellation, with all filter tap coefficients automatically determined via an ondie sign-sign least-mean-square (SS-LMS) adaptation engine. FEXT cancellation is realized by coupling the aggressor signal through a differentiator circuit whose gain is automatically adjusted with a power-detection-based adaptation loop. In conclusion, the proposed architectures in the transmitter side and receiver side together are to be good solution in the high speed I/O serial links to improve the performance by overcome the physical channel loss and adjacent channel noise as the system becomes complicated

DPSK regeneration: phase and amplitude noise suppression based on Kerr medium

The scope of this thesis is to identify and propose new schemes for Deferential Phase Shift Keying (DPSK) regeneration. DPSK modulation format presents increased robustness against ASE noise, which makes it strong candidate for use in long haul transmission systems. To achieve reasonable DPSK regeneration suppression of both the amplitude and phase noise is required. Three types of all-optical regenerators that make use of a Kerr medium, which can be a highly nonlinear fiber are analyzed. The first scheme is based on a modified nonlinear optical loop mirror (NOLM), with a subsequent addition of a bidirectional attenuator (DANOLM). The bidirectional attenuator allows to counterbalance the generation of the phase noise generated by the Gordon Mollenauer effect inside the Kerr medium. The second type of optical regenerator is based on the Self Phase Modulation (SPM) effect and offset filtering. Finally a novel scheme derived from the concepts of two former setups is presented and compared to the previous proposed. The operational conditions for optimum noise rejection are identified for each one of them. Through numerical simulations and detailed benchmarink we identify that our proposal outperforms all the schemes that have been presented previously in literature

Design and applications of advanced optical modulation formats for optical metro/access transmission systems.

光纖通信技術與光網絡在過去三十年間極大地改變了人們的生活。雖然整個光通信行業因為2000年互聯網泡沫的破滅受到了影響，但近年來由於高清電視，移動多媒體和社交網絡的興盛，互聯網對通信網絡傳輸帶寬的需求達到了前所未有的高度，進而推動了光通信行業的再一次興盛。站在行業的高度來看，寬帶接入網無疑是推動行業發展的最主要領域。而實現寬帶接入網的最主要技術則是無源光網絡技術。無源光網絡的本質是一個樹型拓撲的光網絡，其主要的傳輸光纖可被多用戶共享，且在中央基站和用戶之間無任何有源器件，從而大大降低了網絡的成本。然而，在具體實踐中，仍然有許多的技術難題需要解決，例如：無色光網絡單元、突發性傳輸、全雙工傳輸、長距離無源光網絡和網絡功能集成等。這些技術需求亦反應了市場對通信技術發展的要求，及“更快，更便宜，更灵活“。為滿足無源光網絡的技術要求，研究者們從不同的角度提出了各種解決方案，研究領域囊括光傳輸技術、新型器件、系統結構、網絡協議等等。本論文研究從傳輸碼型的角度來解決上述一項或幾項問題。研究碼型包括雙二進制反歸零碼，雙二進制曼切斯特碼，還有常規曼切斯特碼。研究內容則包括上述碼型的產生、接收、傳輸特性和系統應用等等。論文首貳章為概要和背景技術介紹，其餘幾章則按照不同的碼型分類討論。本論文第一項研究課題為雙二進制反歸零碼。相比傳統的歸零碼和反歸零碼，雙二進制反歸零碼具有更大的色散容限，且每個傳輸符號均有能量。我們先研究了它的優勢，調製/解調方法，而後研究了該碼型在無源光網絡中的具體應用，包括10‐Gb/s 全光組播系統和基於重調製的80 公里長距離波分複用無源光網絡系統。第二項研究課題為雙二進制曼切斯特碼型，該碼型的優勢包括較大的時鐘分量，窄帶寬，無直流分量等。我們提出了一種基於直接調製的雙二進制曼切斯特碼產生方法。該方法具有高效，低價，高輸出功率等特點。基於該雙二進制曼切斯特碼發射機，我們實現了70 公里雙向傳輸的波分複用無源光網絡。該系統下行傳輸採用雙二進制曼切斯特碼型，上行傳輸採用直接調製的反射式半導體激光器，所以系統成本大大降低。最後，我們研究了電色散補償技術對於傳統曼切斯特碼型的傳輸性能的改善。所使用的電均衡技術包括前向均衡器、判決反饋均衡器和極大似然估計均衡器。通過離線處理的方法，我們對曼切斯特碼型在三種均衡器下的傳輸性能進行了實驗驗證。研究內容包括前向均衡器和判決反饋均衡器抽頭數的優化、不同採樣率下系統性能、極大似然估計中狀態機個數的影響和不同的曼切斯特接收機的影響等等。The increasing demands for bandwidth have aroused a myriad of industry and academic activities in developing high-speed and cost-effective optical networks,among which optical broad band access networks was the main driving force for such growth in recent years. The most promising solution to optical broadband access network is the passive optical network (PON), which is a point-to-multipoint tree-topology network that connects optical line terminal (OLT) with many optical network units (ONUs) via a long fiber feeder and many short distribution fibers. Promising the concept it is, it raises many detailed technical challenges, such as colorless ONUs, burst mode transmission, bi-directional transmission with mitigated backscattering noise, long-reach PON, and integrating network functionalities. All of the technical requirements are motivated by the “original requirements“ of telecommunication -- faster, cheaper, and more robust.To fulfill the technical requirements, different researchers take different angles to design system and to study the enabling technologies. For example, devices, system architectures, network protocols, etc. In this thesis research, we have tried to deal with one or multiple problems by employing advanced modulation formats for the optical signals. In particular, we have studied IRZ-duobinary, Manchester-duobinary, and Manchester formats, including the modulation/demodulation techniques, transmission properties, and system applications. The research topics are classified according to the type of modulation formats.In the first topic, IRZ-duobinary format is proposed for optical signal transmission. It has desirable properties of large dispersion tolerance (as compared to conventional RZ/IRZ) and finite optical power in each bit. In this study, we firstly show the advantages of IRZ-duobinary and the corresponding modulation techniques. Then, we demonstrate a 10-Gb/s per channel optical multicast overlay scheme and an 80-km-reach system with re-modulated ONU, both in wavelength division multiplexing (WDM) PON.In the second topic, Manchester-duobinary format, which has the advantages including easy clock/level recovery, compressed bandwidth, and zero DC component, is studied. We propose an efficient and cost-effective Manchester-duobinary transmitter by properly modulating a chirp managed laser (CML) with electrical Manchester signal. Then, a cost-effective CLS 70-km-Reach full-duplex WDM-PON with downstream 10-Gb/s Manchester-duobinary signal and upstream 1.25-Gb/s re-modulated NRZ-OOK signal is proposed and experimentally demonstrated. This design simultaneously solves the problems of colorless ONU, bi-directional transmission, and long-reach, using cost-effective system design and devices.Finally, we investigate the performance of electronic dispersion compensation (EDC) technique on 10-Gb/s Manchester coded optical signal, so as to further improve its dispersion tolerance and may enables its applications in long-reach PON. In this study, feed forward equalizer (FFE), decision feedback equalizer (DFE), and maximum-likelihood sequence estimation (MLSE) are employed as the equalizers Utilizing off-line signal processing, the performance of different equalizers with different parameters (number of taps, sampling rates, number of states, etc.) under both cases of single-ended and balanced detection are studied and compared. Experimental results show that the transmission distance of Manchester coded signal can be increased by a factor of three with four-sample-per-symbol FFE-DFE.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Liu, Zhixin.Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.Includes bibliographical references (leaves 128-148).Abstract also in Chinese.Acknowledgement --- p.1Abstract --- p.3摘要 --- p.5Table of contents --- p.7List of figures and tables --- p.13Chapter Chapter 1. --- IntroductionChapter 1.1 --- Optical Broadband Access --- p.18Chapter 1.1.1 --- Bandwidth requirement --- p.19Chapter 1.1.2 --- Passive optical networks --- p.22Chapter 1.2 --- Research Challenge of Next-Generation Optical Access Network --- p.25Chapter 1.2.1 --- Colorless ONU --- p.25Chapter 1.2.2 --- Burst Mode Transmission --- p.27Chapter 1.2.3 --- Backscattering Noise in PON --- p.28Chapter 1.2.4 --- Long-Reach Access Network --- p.30Chapter 1.2.5 --- Enriching Network Functionalities --- p.31Chapter 1.3 --- Major contribution of this thesis --- p.32Chapter 1.3.1 --- IRZ-duobinary transmitter and application --- p.32Chapter 1.3.2 --- Manchester-duobinary transmitter and application --- p.33Chapter 1.3.3 --- Receiver with electronic equalizer for Manchester signal --- p.34Chapter 1.4 --- Outline of this Thesis --- p.35Chapter Chapter 2. --- Optical Modulation Technique and Transmission ImpairmentsChapter 2.1 --- Optical Modulation techniques --- p.38Chapter 2.1.1 --- Chirp managed laser --- p.38Chapter 2.1.2 --- Mach-Zehnder modulator --- p.41Chapter 2.2 --- Transmission Impairments --- p.47Chapter 2.2.1 --- Noise --- p.47Chapter 2.2.2 --- Chromatic dispersion --- p.49Chapter 2.2.3 --- Fiber nonlinearity --- p.50Chapter 2.3 --- Impairment Mitigation Techniques --- p.51Chapter 2.3.1 --- In-line compensation techniques --- p.51Chapter 2.3.2 --- Post-compensation techniques --- p.52Chapter Chapter 3. --- Optical Multicast and Re-modulation Based on Inverse-RZ-duobinary TransmitterChapter 3.1 --- Introduction --- p.53Chapter 3.2 --- IRZ-duobinary transmitter --- p.55Chapter 3.2.1 --- Generation of IRZ-duobinary format --- p.55Chapter 3.2.2 --- Comparison of different configurations of IRZ-duobinary generation --- p.56Chapter 3.3 --- IRZ-duobinary format for optical multicast in WDM-PON --- p.60Chapter 3.3.1 --- Optical multicast in WDM-PON --- p.60Chapter 3.3.2 --- Proposed system architecture --- p.61Chapter 3.3.3 --- Experimental demonstration of the proposed optical multicast system --- p.65Chapter 3.4 --- IRZ-duobinary for long-reach PON --- p.68Chapter 3.4.1 --- Long-reach PON using DI based IRZ-duobinary transmitter --- p.69Chapter 3.4.2 --- Long-reach PON using CML based IRZ-duobinary transmitter --- p.75Chapter 3.5 --- Summary --- p.81Chapter Chapter 4. --- Manchester-duobinary Transmitter for Bi-directional WDM-PONChapter 4.1 --- Introduction --- p.83Chapter 4.2 --- Manchester-duobinary transmitter --- p.85Chapter 4.2.1 --- Mach-Zehnder modulator based Manchester-duobinary transmitter --- p.85Chapter 4.2.2 --- Chirp managed laser based Manchester-duobinary transmitter --- p.87Chapter 4.3 --- Rayleigh noise mitigated bi-directional WDM-PON based on Manchester-duobinary transmitter --- p.94Chapter 4.3.1 --- CLS Bi-directional long-reach WDM-PON. --- p.94Chapter 4.3.2 --- Proposed system architecture --- p.97Chapter 4.3.3 --- Experimental demonstration --- p.99Chapter 4.4 --- Summary --- p.102Chapter Chapter 5. --- Electronic Equalizer for Manchester Coded SignalChapter 5.1 --- Introduction --- p.103Chapter 5.2 --- Electronic equalizer for CD compensation --- p.104Chapter 5.2.1 --- Channel model --- p.104Chapter 5.2.2 --- FFE-DFE --- p.106Chapter 5.2.3 --- MLSE --- p.107Chapter 5.3 --- FFE-DFE for Manchester signal --- p.109Chapter 5.3.1 --- Experimental setup for CD compensation of Manchester signal using FFE-DFE --- p.110Chapter 5.3.2 --- Results and discussion --- p.112Chapter 5.4 --- MLSE equalizer for Manchester signal --- p.121Chapter 5.4.1 --- Experimental setup for CD compensation of Manchester format using MLSE --- p.121Chapter 5.4.1 --- Results and discussion --- p.122Chapter 5.5 --- Summary --- p.124Chapter Chapter 6. --- ConclusionChapter 6.1 --- Summary of this thesis --- p.125Chapter 6.2 --- Future work --- p.127References --- p.128Chapter Appendix: --- p.149Chapter A. --- List of abbreviations --- p.149Chapter B. --- List of publications --- p.15

OPTICAL ACCESS NETWORKS BASED ON 1.5-?m VCSELS

Ph.DDOCTOR OF PHILOSOPH

Digital Linearization of High Capacity and Spectrally Efficient Direct Detection Optical Transceivers

Metropolitan area networks are experiencing unprecedented traffic growth. The provision of information and entertainment supported by cloud services, broadband video and mobile technologies such as long-term evolution (LTE) and 5G are creating a rapidly increasing demand for bandwidth. Although wavelength division multiplexing (WDM) architectures have been introduced into metro transport networks to provide significant savings over single-channel systems, to cope with the ever-increasing traffic growth, it is urgently required to deploy higher data rates (100 Gb/s and beyond) for each WDM channel. In comparison to dual-polarization digital coherent transceivers, single-polarization and single photodiode-based direct-detection (DD) transceivers may be favourable for metropolitan, inter-data centre and access applications due to their use of a simple and low-cost optical hardware structure. Single sideband (SSB) quadrature amplitude modulation (QAM) subcarrier modulation (SCM) is a promising signal format to achieve high information spectral density (ISD). However, due to the nonlinear effect termed signal-signal beat interference (SSBI) caused by the square-law detection, the performance of such SSB SCM DD systems is severely degraded. Therefore, it is essential to develop effective and low-complexity linearization techniques to eliminate the SSBI penalty and improve the performance of such transceivers. Extensive studies on SSB SCM DD transceivers employing a number of novel digital linearization techniques to support high capacity (≥ 100 Gb/s per channel) and spectrally-efficient (net ISD > 2 b/s/Hz) WDM transmission covering metropolitan reach scenarios (up to 240 km) are described in detail in this thesis. Digital modulation formats that can be used in DD links and the corresponding transceiver configurations are firstly reviewed, from which the SSB SCM signalling format is identified as the most promising format to achieve high data rates and ISDs. Following this, technical details of the digital linearization approaches (iterative SSBI cancellation, single-stage linearization filter and simplified non-iterative SSBI cancellation, two-stage linearization filter, Kramers-Kronig scheme) considered in the thesis are presented. Their compensation performance in a dispersion pre-compensated (Tx-EDC) 112 Gb/s per channel 35 GHz-spaced WDM SSB 16-QAM Nyquist-SCM DD system transmitting over up to 240 km standard single-mode fibre (SSMF) is assessed. Net ISDs of up to 3.18 b/s/Hz are achieved. Moreover, we also show that, with the use of effective digital linearization techniques, further simplification of the DD transceivers can be realized by moving electronic dispersion compensation from the transmitter to the receiver without sacrificing performance. The optical ISD limit of SSB SCM DD system finally explored through experiments with higher-order modulation formats combined with effective digital linearization techniques. 168 Gb/s per channel WDM 64-QAM signals were successfully transmitted over 80 km, achieving a record net optical ISD of 4.54 b/s/Hz. Finally, areas for further research are identified

DPSK regeneration: phase and amplitude noise suppression based on Kerr medium

The scope of this thesis is to identify and propose new schemes for Deferential Phase Shift Keying (DPSK) regeneration. DPSK modulation format presents increased robustness against ASE noise, which makes it strong candidate for use in long haul transmission systems. To achieve reasonable DPSK regeneration suppression of both the amplitude and phase noise is required. Three types of all-optical regenerators that make use of a Kerr medium, which can be a highly nonlinear fiber are analyzed. The first scheme is based on a modified nonlinear optical loop mirror (NOLM), with a subsequent addition of a bidirectional attenuator (DANOLM). The bidirectional attenuator allows to counterbalance the generation of the phase noise generated by the Gordon Mollenauer effect inside the Kerr medium. The second type of optical regenerator is based on the Self Phase Modulation (SPM) effect and offset filtering. Finally a novel scheme derived from the concepts of two former setups is presented and compared to the previous proposed. The operational conditions for optimum noise rejection are identified for each one of them. Through numerical simulations and detailed benchmarink we identify that our proposal outperforms all the schemes that have been presented previously in literature