Pham, Tien Thang

Forskningsarbejdet beskrevet i denne afhandling beskriver omfattende eksperimentelle undersøgelser af metoder til kost-effektive høj hastigheds optiske og trådløse kommunikationssystemer. Hovedbidragene i afhandlingen har udvidet state-of-the-art indenfor to områder: Høj-hastigheds optisk/trådløs integration, og avancerede modulationsformater til intensitets modulation og direkte detektion (IM/DD).Vedrørende optisk/trådløs integration, fokuserer afhandlingen på integration af bredbånds ultrawide-band (UWB) og 60-GHz trådløse systemer med optiske access netværk for at distribuere trådløse tjenester til personlige netværk (PAN). Fotoniske teknologier til generation og distribution af gigabit ultrawide-band (UWB) og 60-GHz signaler er foreslået og demonstreret. To nye metoder til optisk generation af UWB signaler, der overholder Federal Communications Commission (FCC) krav, samt integrationen af disse i passive optiske netværk (PON), er foreslået og demonstreret. Ydelsen af UWB og andre typer trådløse og kablede signaler er undersøgt eksperimentelt i forskellige arkitekturer, bl.a. heterogene fiber og trådløse netværk samt kombineret kommunikation og sensor-netværk. For 60-GHz radio-over-fiber (RoF) systemer er muligheden for at opnå en simplificering gennem en kombination af multimode fiber (MMF) og singlemode fiber (SMF) til gigabit data over 60-GHz forbindelser eksperimentelt undersøgt. Derudover er kvaliteten af videosignaler distribueret over et simplificeret 60-GHz system undersøgt eksperimentelt og teoretisk ved at analysere forholdet mellem forvrængning introduceret af videokodning og forvrængning introduceret i transmissionskanalen.Udover optisk/trådløs integration, udforsker denne afhandling teknikker til høj-hastigheds baseband signaler i IM/DD forbindelser. For at forbedre den spektrale effektivitet, er en ny metode for avancerede modulationsformater introduceret. Denne baserer sig på anvendelsen af bærebølgefrekvenser, der er mindre end signalets symbolrate, eksempelvis halvdelen og en fjerdedel af ymbolraten. Kvadratur amplitude modulation (QAM) ved en fjerdedel hhv. halvdelen af signalets symbolrate giver således en 37.5% hhv. en 25% forbedring i spektral effektivitet.Anvendeligheden af føromtalte halv-cyklus QAM er blevet demonstreret ved at transmittere et 10-Gbps 4-QAM signal over 20 km SMF og et 9-Gbps signal over 1 km MMF. Begge systemer anvender direkte modularede vertikal kavitet overflade emitterende lasere (VCSELs) og simple elektriske sender/modtager implementeringer. I forhold til tilsvarende konventionelle binært amplitudemodulerede signaler opnåedes en 3-dB forbedring af tolerancen overfor kromatisk dispersino og en 1,5-dB forbedring at tolerancen overfor inter-modal dispersion; begge ved en bit-fejl sansynlighed på 10&amp;#x100000;5.Det kan konkluderes at de i denne afhandling foreslåede teknikker demonstrerer anvendeligheden af optiske teknologier til distribution af gigabit trådløse signaler. Endvidere demonstreres integrérbarheden af af trådløse og optiske signaler i en fælles platform. Derudover er de mulige forbedringer i spektral effektivitet og dispersionstolerance ved anvendelse af halvcyklus QAM modulation demonstreret.The research work described in this thesis is devoted to experimental investigation of techniques for cost-effective high-speed optical communications supporting both wired and wireless services. The main contributions of this thesis have expanded the state-of-the-art in two main areas: high-speed optical/wireless integration and advanced modulation formats for intensity modulation with direct detection (IM/DD) optical systems.Regarding optical/wireless integration, this thesis focuses on integration of broadband ultra-wide band (UWB) and 60-GHz band wireless systems into optical fiber access networks to distribute wireless services in personal area networks (PANs). Photonic technologies to generate and distribute gigabit UWB and 60-GHz-band signals are proposed and demonstrated.Two novel methods are proposed and demonstrated to optically generate Federal Communications Commission (FCC)-compliant gigabit UWB signals and integrate them into baseband wavelength division multiplexingpassive optical networks (WDM-PONs). Performance of UWB signals and other wired/wireless signals in different scenarios including heterogeneous wired and wireless access networks, converged communication and sensing networks are experimentally assessed. For 60-GHz radio-over-fiber (RoF) systems, possibilities to simplify the system architecture and to use multimode fiber (MMF) together with single-mode fiber (SMF) to transport gigabit data at 60-GHz band are experimentally investigated. Additionally, the quality of video services distributed in a simplified 60-GHz RoF system is both experimentally and theoretically studied by analyzing the tradeoff between the distortion introduced by the video coding and distortion introduced by the optical/wireless transmission channel.Next to optical/wireless integration, this thesis explores techniques for delivery of high speed baseband signals in IM/DD optical links. To improve spectral efficiency (SE), a novel approach is introduced to implement advanced modulation formats, using subcarrier frequencies below the baud rate including half and quarter the baudrate. Compared to conventional single subcarrier modulation, quarter-cycle and half-cycle quadrature amplitude modulation (QAM) achieve a improvement of the SE by 37.5% and 25%, respectively. The feasibility of half-cycle QAM signals for IM/DD optical links is demonstrated by transmission of a 10-Gbps half-cycle 4-QAM signal over 20-km SMF and a 9-Gbps 4-QAM signal over 1 km MMF both using VCSELs and simple electrical transceiver structures. The proposed approach results in the 3 dB improvement of chromatic dispersion tolerance and 1.5 dB improvement of modal dispersion tolerance at the bit-error-ratio (BER) of 10&amp;#x100000;5 compared to similar OOK systems operating at the same bitrate.In conclusion, techniques proposed in this thesis demonstrate the feasibility of employing photonic technologies for the generation and distribution of gigabit wireless signals. They also demonstrate seamless integrability of wired and wireless signals into a unified optical fiber platform. Additionally, half-cycle QAM modulation has prospects to increase SE and bit rates in high-speed short-range optical communication systems

Online Research Database In Technology

Data transmission techniques for short-range optical fiber and wireless communication links

http://orbit.dtu.dk/ws/files/52006404/main_PTIT_final.pdf

Data transmission techniques for short-range optical fiber and wireless communication links

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Online Research Database In Technology