Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection

Free Space Optical (FSO) communications receive growing attention for use in high data rates wireless link with recent commercialization successes. It is an interesting solution to achieve high bandwidth in the ‘last-mile’ problem with economical and fast deployment. However, in the poor weather suc...

Full description

Saved in:

Bibliographic Details
Main Author:	Hitam, Salasiah
Format:	Thesis
Language:	English English
Published:	2006
Subjects:	Free space optical interconnects - Case studies
Online Access:	http://psasir.upm.edu.my/id/eprint/5143/1/FK_2006_37.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!

id	my-upm-ir.5143
record_format	uketd_dc
spelling	my-upm-ir.51432013-05-27T07:20:41Z Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection 2006 Hitam, Salasiah Free Space Optical (FSO) communications receive growing attention for use in high data rates wireless link with recent commercialization successes. It is an interesting solution to achieve high bandwidth in the ‘last-mile’ problem with economical and fast deployment. However, in the poor weather such as the heavy rainfall and low visibility lead to degradation of the links performance, particularly over ranges of several hundred meters or longer. Rare usage of FSO communications might be related to factors which are classified as scintillation, absorption, and scattering. In this purpose of studies, the heavy rainfall and low visibility data in Subang Airport, Malaysia were used for the analysis on conventional technique that is Intensity Modulation/Direct Detection (IM/DD) and a new technique namely Double Carrier Modulation/Differential Detection (DCM/Diff.D) as the worst case scenario.Currently, most FSO communication systems are using the IM/DD which are still subjected to many problems. The main problems associated with FSO transmission systems are; atmospheric loss, geometric loss, mispointing loss, and the inability of the receiver circuit to regenerate the transmitted bits because of low signal power. Another prevalent problem is that of its masking noises. The recovery technique in the IM/DD technique uses an injected voltage level as a threshold into a decision circuit, which decides whether the incoming bit is a ‘0’ or a ‘1’. This technique has two inherent problems; the instability of the injected threshold voltage, and the complexity of a dynamic threshold processing. Due to these problems, a new technique based on the automatic decision making known as DCM/Diff.D is provided to improve the transmissions. The performance of IM/DD and DCM/Diff.D was simulated by using commercial simulation software, OptiSystem Version 3.1 and 4. From the simulation results, it appears clearly that the DCM/Diff.D technique improves for more than twice the distance supported by the IM/DD technique under the conditions of heavy rainfall and hazy days. The theoretical development on probability of error and digital signal-to-noise ratio for the worst case scenario also support these results. Another outcome in this thesis is the theoretical derivation on positioning a passive reflector with a time delay produced can be acceptable until 2.5 Gbps. Free space optical interconnects - Case studies 2006 Thesis http://psasir.upm.edu.my/id/eprint/5143/ http://psasir.upm.edu.my/id/eprint/5143/1/FK_2006_37.pdf application/pdf en public phd doctoral Universiti Putra Malaysia Free space optical interconnects - Case studies Faculty of Engineering English
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English English
topic	Free space optical interconnects - Case studies
spellingShingle	Free space optical interconnects - Case studies Hitam, Salasiah Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection
description	Free Space Optical (FSO) communications receive growing attention for use in high data rates wireless link with recent commercialization successes. It is an interesting solution to achieve high bandwidth in the ‘last-mile’ problem with economical and fast deployment. However, in the poor weather such as the heavy rainfall and low visibility lead to degradation of the links performance, particularly over ranges of several hundred meters or longer. Rare usage of FSO communications might be related to factors which are classified as scintillation, absorption, and scattering. In this purpose of studies, the heavy rainfall and low visibility data in Subang Airport, Malaysia were used for the analysis on conventional technique that is Intensity Modulation/Direct Detection (IM/DD) and a new technique namely Double Carrier Modulation/Differential Detection (DCM/Diff.D) as the worst case scenario.Currently, most FSO communication systems are using the IM/DD which are still subjected to many problems. The main problems associated with FSO transmission systems are; atmospheric loss, geometric loss, mispointing loss, and the inability of the receiver circuit to regenerate the transmitted bits because of low signal power. Another prevalent problem is that of its masking noises. The recovery technique in the IM/DD technique uses an injected voltage level as a threshold into a decision circuit, which decides whether the incoming bit is a ‘0’ or a ‘1’. This technique has two inherent problems; the instability of the injected threshold voltage, and the complexity of a dynamic threshold processing. Due to these problems, a new technique based on the automatic decision making known as DCM/Diff.D is provided to improve the transmissions. The performance of IM/DD and DCM/Diff.D was simulated by using commercial simulation software, OptiSystem Version 3.1 and 4. From the simulation results, it appears clearly that the DCM/Diff.D technique improves for more than twice the distance supported by the IM/DD technique under the conditions of heavy rainfall and hazy days. The theoretical development on probability of error and digital signal-to-noise ratio for the worst case scenario also support these results. Another outcome in this thesis is the theoretical derivation on positioning a passive reflector with a time delay produced can be acceptable until 2.5 Gbps.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Hitam, Salasiah
author_facet	Hitam, Salasiah
author_sort	Hitam, Salasiah
title	Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection
title_short	Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection
title_full	Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection
title_fullStr	Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection
title_full_unstemmed	Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection
title_sort	improvement of free space optical communications using double carrier modulation/differential detection
granting_institution	Universiti Putra Malaysia
granting_department	Faculty of Engineering
publishDate	2006
url	http://psasir.upm.edu.my/id/eprint/5143/1/FK_2006_37.pdf
_version_	1747810360373542912

Improvement Of Free Space Optical Communications Using Double Carrier Modulation/Differential Detection

Similar Items