Optically amplified free-space optical communication systems

Aladeloba, Abisayo Olufemi (2013) Optically amplified free-space optical communication systems. PhD thesis, University of Nottingham.

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Abstract

This thesis investigates terrestrial atmospheric FSO communication systems operating under the influence of turbulence-induced scintillation, beam spreading, optical interchannel crosstalk, amplified spontaneous emission noise and pointing errors. On-off keying-non–return-to-zero (OOK-NRZ) and digital pulse position (DPPM) are the modulation schemes used for the calculations.

The possibility of using sophisticated performance evaluation techniques such as moment generating function (MGF)-based Chernoff bound (CB), modified Chernoff bound (MCB) and saddlepoint approximation (SPA) for terrestrial DPPM and OOK-NRZ–based FSO communication systems employing optical amplification are investigated and compared with the conventional Gaussian approximation (GA) method. Relative to the other techniques, the MCB can be considered a safe estimation method for practical systems since it provides an upper bound upon the BER.

The turbulent optically preamplified DPPM FSO receiver employing integration over a time slot and comparing the results to choose the largest slot, is seen to give better advantage (about 7 - 9 dB) compared to an equivalent employing OOK-NRZ signalling. The atmospheric turbulence-induced spreading of the beam, ASE noise, and pointing error are seen to combine in a problematic way resulting in high BERs, depending on the size of the receiver and the beam’s jitter standard deviation.

Using FSO communication for the distribution links of a passive optical network-like wavelength division multiplexing access network is investigated in the presence of atmospheric turbulence, ASE noise and interchannel crosstalk. The results show that, for clear atmosphere, FSO distribution link length up to 2000 m can be reliably used (depending on turbulence strength) to achieve human eye safety and high capacity access networks. Also, error floors occur due to turbulence accentuated crosstalk effect for the cases of (i) signal turbulent, but crosstalk not and (ii) crosstalk turbulent, but signal not.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Phillips, A.
Woolfson, M.S.
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK5101 Telecommunication
Faculties/Schools: UK Campuses > Faculty of Engineering > Department of Electrical and Electronic Engineering
Item ID: 13304
Depositing User: EP, Services
Date Deposited: 17 Sep 2013 09:07
Last Modified: 14 Sep 2016 06:44
URI: http://eprints.nottingham.ac.uk/id/eprint/13304

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