Experimental demonstration of all-optical CDMA using bipolar codes

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dc.contributor.advisorYoung, James F.en_US
dc.creatorDennis, Tasshien_US
dc.date.accessioned2009-06-04T08:00:56Zen_US
dc.date.available2009-06-04T08:00:56Zen_US
dc.date.issued1999en_US
dc.description.abstractFiber optic networks capable of supporting a large pool of subscribers, many simultaneous users, and high data rates are receiving heightened interest as solutions to a growing communications need. The experiments reported in this study constitute the first experimental demonstration of a novel bipolar equivalent code-division multiple-access (CDMA) scheme. The sophisticated encoding increases noise tolerance, provides user security, and enables network flexibility. The scheme is based on an established bipolar radio frequency (RF) technique adapted to the unipolar optical domain. Whereas the phase of an RF signal can be readily detected, the high carrier frequency ( ∼ 200 THz at 1.5 mum) of an optical wave necessitates that optical signals be detected and processed solely by intensity. Asynchronous operation makes the CDMA scheme data rate independent, while all-optical implementation avoids the bandwidth limitations imposed by electrical processing. A proof-of-principle experiment was conducted by spectrally encoding an erbium-doped superfluorescent fiber source (SFS) using a diffraction grating and an amplitude mask. The optical properties of the system were measured and the bipolar correlation of codes was verified. The practical implementation of the scheme was investigated by the design, construction, and operation of a fiber-based testbed. Correlation measurements performed with modulated signals confirmed that the scheme can recover a binary information symbol while rejecting multiple access interference. A theoretical analysis of the optical correlation process was conducted, which identified key optical parameters important to future implementations. The theory of excess noise associated with the photodetection of a thermal source was considered, followed by noise measurements of a light bulb and the erbium-doped SFS used for spectral encoding. Finally, the ability of the proposed scheme to effectively transmit data was investigated. Signal-to-noise-ratio and eye diagram measurements of the testbed were recorded. Bit-error rate (BER) measurements were conducted for various network scenarios, including operation with one and two active users, as well as with varying amounts of broadband optical interference. The analysis of the BER measurements addresses the limitations due to excess noise, the impact of imperfect correlation performance) and the anticipated capacity for multiple users.en_US
dc.format.extent121 p.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.callnoTHESIS E.E. 1998 DENNISen_US
dc.identifier.citationDennis, Tasshi. "Experimental demonstration of all-optical CDMA using bipolar codes." (1999) Diss., Rice University. <a href="https://hdl.handle.net/1911/19372">https://hdl.handle.net/1911/19372</a>.en_US
dc.identifier.urihttps://hdl.handle.net/1911/19372en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectElectronicsen_US
dc.subjectElectrical engineeringen_US
dc.subjectOpticsen_US
dc.titleExperimental demonstration of all-optical CDMA using bipolar codesen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentElectrical Engineeringen_US
thesis.degree.disciplineEngineeringen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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