Improved Nonlinear Model Implementation for VCSEL Behavioral Modeling in Radio-Over-Fiber links

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Advances in local area optical data communication systems

This paper reviews optical fibre technology for local area optical communications systems. Technologies used in local systems include single and multimode fibre, single and multimode lasers, optical modulators, photodetectors, wavelength division multiplexing, multilevel modulation formats, electronic packet switching, electronic equalization and error correction. These methods have enabled the local area optical link data rate to increase from 0.1 Gb/s in 1990 to nearly a Tb/s in 2019. The challenges to increasing link data rates further, whilst reducing the transmitted power per bit, at reduced cost are discussed. Potential technical solutions and newly proposed methods which might address these challenges are highlighted

Performance of low-cost radio-over-fibre systems

The research presented in this thesis has focused on the use of radio-over-fibre (RoF) technology for improving the quality of mobile/wireless coverage within buildings. The primary aim was to minimise overall system costs by employing commercially available components. For this purpose, a distributed antenna system using low-cost vertical-cavity surface-emitting lasers (VCSELs) operating at 850 nm and multimode fibre (OM1/OM2) has been designed and implemented. A detailed link budget analysis has been performed which allows for the prediction of maximum achievable ranges for the transmission of different wireless systems over the RoF link, while taking into account practical restrictions that are important for bidirectional link operation (e.g. crosstalk and noise emissions). The analysis indicates that when optimised component parameter values are utilised, reasonable cell sizes may be achieved for systems such as GSM, UMTS and WLAN. The link budget predictions were verified for the transmission of ‘real’ WLAN signals over the designed RoF link and complete coverage of a standard office room was demonstrated. The majority of previous research into low-cost RoF links has primarily involved characterisation of the optical path. In this investigation, signal strength and throughput measurements were conducted for the combined optical and wireless paths in order to verify the operation of the complete fibre-fed WLAN system. Throughput values close to 5 Mbps for IEEE 802.11b and 20 Mbps for IEEE 802.1 lg were recorded. Additionally, the transmission of different combinations of emulated mobile/wireless systems in a dual-band configuration over another radio-over-fibre link (also employing 850 nm VCSELs and MMF) has been successfully demonstrated. Experimental investigations have been carried out for the first time to analyse the performance of WLAN-over-fibre networks using different MAC mechanisms such as fragmentation and the use of RTS/CTS in the presence of hidden nodes. Finally, scenarios involving multiple clients accessing a single remote antenna unit and multiple remote antenna units being fed by a single access point have been demonstrated

Polymer waveguide based optical interconnects for high-speed on-board communications

This dissertation presents a study of multimode polymer waveguide technology for use in board-level communication links for future data centres and supercomputers. The motivation for this work comes from the severe interconnection bandwidth challenges faced by the conventional electrical interconnections technology and the potential performance advantages of optical interconnections. This thesis presents the work to address the bandwidth bottleneck by developing high-bandwidth multimode polymer waveguides. The use of multimode waveguides provides relaxed alignment tolerances enabling low-cost assembly tools. Siloxane polymer materials developed by Dow Corning Corporation are chosen to form the waveguides in this work due to their favourable optical properties (optical losses as low as 0.03 dB/cm and the ability to withstand temperatures in excess of 350 °C) that allow the waveguides to be directly integrated on printed circuits boards (PCBs) using conventional manufacturing processes. Useful design rules for the use of the multimode polymer waveguides are theoretically derived while the bandwidth-length products are investigated under various launch conditions. Frequency-domain measurements and ultra-short pulse measurements are then carried out to investigate the bandwidth performance of the polymer waveguides under different launch conditions and with lateral misalignments. The instrument-limited frequency-domain measurements show that these waveguides exhibit bandwidth-length products (BLPs) of at least 35 GHz×m, while the pulse broadening measurements reveal the actual BLPs to be in excess of 70 GHz×m under a 50 μm multimode-fibre (MMF) launch and 100 GHz×m for a restricted launch across a wide range of input offsets (>±10 μm). This shows the potential for data transmission rates of 100 Gb/s and beyond over a single waveguide channel. A theoretical model is developed using the measured refractive index profile and good agreement with the above experimental results is found. The effects of graded refractive index profiles on the performance of waveguide components (bends, crossings) are also investigated, demonstrating that appropriate refractive index engineering can provide enhanced waveguide loss performance while exhibiting adequate bandwidth. Waveguide bends with excess loss below 1 dB for a radius >6 mm, crossings with loss less than 0.02 dB/crossing while exhibiting adequate link bandwidth (>47 GHz×m) can be achieved for a MMF launch. On this basis, advanced modulation formats are investigated across the board-level waveguide links for further increasing the on-board data rates. Record NRZ-based 40 Gb/s and 56 Gb/s PAM-4 based data transmission over a 1 m long multimode polymer spiral waveguide are theoretically and experimentally demonstrated

Broadband Receiver Electronic Circuits for Fiber-Optical Communication Systems

The exponential growth of internet traffic drives datacenters to constantly improve their capacity. As the copper based network infrastructure is being replaced by fiber-optical interconnects, new industrial standards for higher datarates are required. Several research and industrial organizations are aiming towards 400 Gb Ethernet and beyond, which brings new challenges to the field of high-speed broadband electronic circuit design. Replacing OOK with higher M-ary modulation formats and using higher datarates increases network capacity but at the cost of power. With datacenters rapidly becoming significant energy consumers on the global scale, the energy efficiency of the optical interconnect transceivers takes a primary role in the development of novel systems. There are several additional challenges unique in the design of a broadband shortreach fiber-optical receiver system. The sensitivity of the receiver depends on the noise performance of the PD and the electronics. The overall system noise must be optimized for the specific application, modulation scheme, PD and VCSEL characteristics. The topology of the transimpedance amplifier affects the noise and frequency response of the PD, so the system must be optimized as a whole. Most state-of-the-art receivers are built on high-end semiconductor SiGe and InP technologies. However, there are still several design decisions to be made in order to get low noise, high energy efficiency and adequate bandwidth. In order to overcome the frequency limitations of the optoelectronic components, bandwidth enhancement and channel equalization techniques are used. In this work several different blocks of a receiver system are designed and characterized. A broadband, 50 GHz bandwidth CB-based TIA and a tunable gain equalizer are designed in a 130 nm SiGe BiCMOS process. An ultra-broadband traveling wave amplifier is presented, based on a 250 nm InP DHBT technology demonstrating a 207 GHz bandwidth. Two TIA front-end topologies with 133 GHz bandwidth, a CB and a CE with shunt-shunt feedback, based on a 130 nm InP DHBT technology are designed and compared

Wideband integrated circuits for optical communication systems

The exponential growth of internet traffic drives datacenters to constantly improvetheir capacity. Several research and industrial organizations are aiming towardsTbps Ethernet and beyond, which brings new challenges to the field of high-speedbroadband electronic circuit design. With datacenters rapidly becoming significantenergy consumers on the global scale, the energy efficiency of the optical interconnecttransceivers takes a primary role in the development of novel systems. Furthermore,wideband optical links are finding application inside very high throughput satellite(V/HTS) payloads used in the ever-expanding cloud of telecommunication satellites,enabled by the maturity of the existing fiber based optical links and the hightechnology readiness level of radiation hardened integrated circuit processes. Thereare several additional challenges unique in the design of a wideband optical system.The overall system noise must be optimized for the specific application, modulationscheme, PD and laser characteristics. Most state-of-the-art wideband circuits are builton high-end semiconductor SiGe and InP technologies. However, each technologydemands specific design decisions to be made in order to get low noise, high energyefficiency and adequate bandwidth. In order to overcome the frequency limitationsof the optoelectronic components, bandwidth enhancement and channel equalizationtechniques are used. In this work various blocks of optical communication systems aredesigned attempting to tackle some of the aforementioned challenges. Two TIA front-end topologies with 133 GHz bandwidth, a CB and a CE with shunt-shunt feedback,are designed and measured, utilizing a state-of-the-art 130 nm InP DHBT technology.A modular equalizer block built in 130 nm SiGe HBT technology is presented. Threeultra-wideband traveling wave amplifiers, a 4-cell, a single cell and a matrix single-stage, are designed in a 250 nm InP DHBT process to test the limits of distributedamplification. A differential VCSEL driver circuit is designed and integrated in a4x 28 Gbps transceiver system for intra-satellite optical communications based in arad-hard 130nm SiGe process

Enabling Technology in Optical Fiber Communications: From Device, System to Networking

This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking