Arlunno, Valeria

Denne afhandling omhandler design og evaluering af digitale signalbehandlingsalgoritmer for kohærent optisk kommunikation. Forskningsresultaterne præsenteret rapporterer om transmissionsegenskaber for modulationsfor-mater med høj spektral effektivitet som benytter højere ordens modulationsformater og polarisationsmultipleksing. Avanceret signalbehandling i modtageren åbner mulighed for robuste og fleksible højkapacitets optiske netværk og er derfor et grundelement i næste generations kohærente modtagere.Der er to hovedbidrag i denne afhandling: Det første er brugen af udligning med tilbagekobling og det andet er signalbehandlingsalgoritmer for en optisk kohærent modtager som benytter OFDM og automatisk genkendelse af modulationsformater. Udligning med tilbagekobling kombineret med kodning er blevet undersøgt for transmissionssystemer som benytter højere ordens modulationsformater og for transmissionssystemer med tætpakkede optiske kanaler.Forskningshøjdepunkter i denne afhandling er evaluering og implementering af en ny metode for fælles kodning og udligning, såkaldt Turbo Equalization (TE) . Denne metode er vist at være meget nyttig til at modvirke signalforvrængning for højere ordens modulationsformater som 16 QAM. Den foreslåede TE algoritme er også blevet demonstreret for dispersionskompenserede links. Endvidere er den udvidede version af TE algoritmen blevet demonstreret for optiske links som ikke benytter dispersionskom-penserende fiber. Den nye TE algoritme benytter en mindre kompleks foldningskode i forhold til tidligere publicerede algoritmer. For at opretholde de strenge krav om spektral effektivitet undersøges også anvendelse af en digital adaptiv udligner til rekonfigurerbare og ultra-tætte WDM systemer. En algoritme baseret på beslutningstilbagekoblet udligning er anvendt for at forbedre båndbreddeudnyttelsen uden brug af optiske adskillelsesbånd. Digitale signalbehandlingsalgoritmer for udligning af OFDM signaler er også undersøgt sidst i afhandlingen og er blevet verificeret eksperimentelt for radio-over-fibre systemer og systemer der benytter forskellige modulationsformater.For at konkludere, denne afhandling demonstrerer den fleksibilitet og robusthed der kan opnås med avancerede digitale signalbehandlingsteknikker for fremtidens højhastigheds optiske netværk med høj kapacitet. Endvidere viser den nogle muligheder for lovende udligningsteknikker der anvender tilbagekobling understøttet af kodning såsom TE.This PhD thesis addresses the design and performance evaluation of advanced Digital Signal Processing (DSP) algorithms for coherent optical fiber transmission systems. The research results presented in this thesis report on transmission of highly spectrally efficient optical communication systems employing multiplexing techniques with polarization multiplexing and multi-level modulations format. Advanced digital signal processing techniques offer robustness and flexibility for next generation high capacity optical fibre networks and are therefore considered as key building blocks in next generation digital coherent receivers.The research results presented in this thesis are pioneering in two areas: first the use of feedback equalization structures and second the use of digital signal processing for receiver structure supporting Orthogonal Frequency Division Multiplexing (OFDM) and reconfigurable format detection. Feedback equalization structure have been investigated in high order modulation formats transmission, when combined with coding techniques, and for closed spaced multiplexing scenario. Highlight results presented in this PhD thesis include evaluation and implementation of a novel approach based on joint encoding and equalization technique, known as Turbo Equalization (TE). This scheme is demonstrated to be powerful in transmission impairments mitigation for high order modulations formats, such as 16 Quadrature Amplitude Modulation (QAM), considered a key technology for high speed high capacity optical links thanks to their increased spectral efficiency. The proposed TE algorithm is successfully applied in dispersion managed link transmission. Then, an extension of the TE algorithm is applied to uncompensated link transmission scenario. Moreover the new proposed approach uses a lower complexity convolutional code compared to state of the art reports.Furthermore, in order to fulfill the strict constrains of spectral efficiency, this thesis shows the application of digital adaptive equalizer for reconfigurable and Ultra Dense Wavelength Division Multiplexing (U-DWDM)transmission. A feedback structure based on Decision Feedback Equalizer (DFE) algorithm is proposed to improve the overall bandwidth utilization reducing the undesired spectral guard bands.Last, digital signal processing (DSP) algorithms are studied to equalize OFDM signal. The experimental demonstrations support Radio-over-Fiber (RoF) transmission system for a stand alone case and mixed modulation mixed bit rates transmission scheme.In conclusion, this PhD thesis demonstrates the flexibility, upgrade-ability and robustness offered by rising advanced digital signal processing techniques, for future high-speed, high-capacity optical networking. Furthermore, it opens the prospects for next generation feedback equalization techniques supported by coding such as Turbo Equalization

Online Research Database In Technology

Advanced Equalization Techniques for Digital Coherent Optical Receivers

http://orbit.dtu.dk/ws/files/87698154/ValeriaArlunnoFinalThesis.pdf

Advanced Equalization Techniques for Digital Coherent Optical Receivers

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Online Research Database In Technology