Performance issues in hybrid fiber radio communication systems due to nonlinear distortion effects in laser transmitters

With the increasing demand for broadband services, it is expected that hybrid fiber radio systems may be employed to provide high capacity access networks for both mobile and fixed users. In these systems, the radio frequency data signals are modulated onto an optical carrier at a mobile switching centre and then sent over fiber to a number of base stations, before being transmitted over air to the users. A possible method of generating the optical radio frequency data signals for distribution over fiber is to directly modulate the electrical signal onto an optical carrier using a laser diode. The major problem with this technique is that nonlinearities in electncal-to-optical conversion may seriously degrade the system performance. In this work we initially examined the distribution of a wideband code division multiple access signal (centered around 6 GHz) through an optically fed microwave system. Our results show that the adjacent channel leakage ratio is degraded from -52 to -32 dBc after passing through the optical system. We then examined the technique of externally injecting light into the directly modulated laser, to extend the bandwidth of the laser diode and hence, increase it’s linear region to beyond the frequency of interest With this technique an improvement of over 10 dB in the adjacent channel leakage ratio of the signal was achieved. We subsequently went on to examine the distribution of a 5-channel radio frequency signal (each channel carrying 10 Mbit/s) through a hybrid fiber system As in the previous work, we examined how external light injection into the directly modulated laser could be used to improve system performance, and our results show an improvement of up to 5 dB. Finally a model was designed using Matlab, which simulated the 5-channel system mentioned above. It used the laser rate equations to mimic the nonlinear effects of the laser diode Good correlation was observed between experimental and simulated results

Optical Communication

Optical communication is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters cover general concepts of optical communication, components, systems, networks, signal processing and MIMO systems. In recent years, optical components and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on optical devices, networking, signal processing, and MIMO systems and other enhanced functions for optical communication. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries

Enhancing the performance of spread spectrum techniques in different applications

Spread spectrum, Automotive Radar, Indoor Positioning Systems, Ultrasonic and Microwave Imaging, super resolution technique and wavelet transformMagdeburg, Univ., Fak. für Elektrotechnik und Informationstechnik, Diss., 2006von Omar Abdel-Gaber Mohamed Al

Sensors and Systems for Indoor Positioning

This reprint is a reprint of the articles that appeared in Sensors' (MDPI) Special Issue on “Sensors and Systems for Indoor Positioning". The published original contributions focused on systems and technologies to enable indoor applications

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

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

Investigation of stimulated Brillouin scattering effects in radio over fiber distribution systems

Because of the emerging demand for bandwidth, future wireless access networks are likely to use high frequency microwave signals as the access media. Hence, radiofrequency (RF) signals need to be processed and transmitted with higher bandwidth in many applications. However, the attenuation of RF signals in traditional transmission media increases rapidly when the frequencies of the signal increase. On the other hand, optical fiber has emerged as an alternative and promising transmission medium in which RF modulated optical carriers can be transmitted and distributed with very low loss. This kind of hybrid radio/fiber system or Radio over Fiber (RoF) system provides good synergy between optics and radio. This thesis first introduces optical and radio communication systems, and provides a review of the RoF systems for wireless access networks. The research then explores the effects of Stimulated Brillouin Scattering (SBS) in RoF distribution networks, and shows that it can seriously degrade the performance of radio-over-fiber systems in which a high transmission power is required. The work then goes onto look at how pre-filtering of the optical microwave signal can simultaneously perform Single Sideband (SSB) filtering to overcome the effects of signal fading due to dispersion, in addition to reducing the effect of SBS on signal transmission. Subsequently, the thesis investigates how to overcome the SBS effect by changing the modulation depth of the optical microwave signal. These experiments show that increasing the modulation index may increase the Brillouin threshold, as it is primarily the carrier power that induces the SBS effect due to its narrow linewidth. In this way we can further reduce the limitations on system performance due to SBS

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion