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Laser Frequency Offset Compensation in Coherent Optical Fiber Communication Links
KTH, School of Information and Communication Technology (ICT).
2017 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

Optical Communications play a critical role in the telecommunications world. They are able to provide a big amount of data and to complement the Wireless Communications. Within the Optical Communications we can find different detection techniques: Direct Detection and Coherent Detection. Direct Detection has been the most used; it modulates the amplitude of the signal to send the information. However, with the development of Digital Signal Processing techniques, Coherent Detection is getting more important due to it allows the modulation of the amplitude and phase of the signal. For that reason, we are able to use new modulations and to increase the amount of data that we can send in the same bandwidth than with Direct Detection.

The use of this detection technic also comes with new problems that have to be solved if we want a correct performance of the whole system. One of these problems that we will find is the Frequency Offset of the lasers, this thesis project is focused on its study and correction with the use of high order modulations (16 or 64-Quadrature Amplitude Modulation).

In order to correct this Frequency Offset three new algorithms have been developed in this thesis with MatLab: QPSK Partitioning Based FOC, QPSK Partitioning Differential Phase Based FOC and Improved QPSK Partitioning Differential Phase Based FOC. These algorithms will be compared with a reference algorithm (BPS Based FOC) that is already working, and it has been provided by the research group formed by KTH Materials and Nano Physics together with the research institute Acreo.

The results show that with low Frequency Offset, the algorithm that works best is the reference algorithm (BPS Based FOC). However, with high Frequency Offset two of the three developed algorithms have a better and more stable performance (QPSK Partitioning Differential Phase Based FOC and Improved QPSK Partitioning Differential Phase Based FOC).

Place, publisher, year, edition, pages
2017. , p. 39
Series
TRITA-ICT-EX ; 2017:109
Keywords [en]
Quadrature Amplitude Modulation, Light Emitting Diode, Light Amplification by Stimulated Emission of Radiation − IM/DD: Intensity Modulation / Direct Detection − COC: Coherent Optical Communications, Bit Error Rate, Digital Signal Processing, Inphase/Quadrature, Local Oscillator, Analog to Digital Converter, Optical Signal to Noise Ratio, Frequency Offset, Carrier Phase Recovery, Frequency Offset Compensation, Symbol Time, Triangular Edge
National Category
Computer and Information Sciences
Identifiers
URN: urn:nbn:se:kth:diva-227804OAI: oai:DiVA.org:kth-227804DiVA, id: diva2:1205329
Subject / course
Information and Communication Technology
Educational program
Bachelor of Science - Information and Communication Technology
Examiners
Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-14Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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Output format
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