Online ISSN
1751-8776
Print ISSN
1751-8768
IET Optoelectronics
Volume 4, Issue 2, April 2010
Volumes & issues:
Volume 4, Issue 2
April 2010
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- Author(s): L.-C. Yang ; C.-C. Huang ; S.-C. Yang ; S.-L. Tsao
- Source: IET Optoelectronics, Volume 4, Issue 2, p. 51 –56
- DOI: 10.1049/iet-opt.2008.0042
- Type: Article
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A new encoder/decoder structure, called the ‘dynamic encoder/decoder’, for optical code-division-multiple-access (CDMA) network applications is proposed. Two theoretical models, including Z-transform in RF signals and electromagnetic fields in optical signals, are built to describe the signal transmission characteristics for the dynamic encoder/decoder. Suitable optical parameters of the dynamic optical encoder/decoder can be determined easily by comparing the frequency responses of the electrical control signals and the optical fields. - Author(s): H.A. Khan and A.A. Rezazadeh
- Source: IET Optoelectronics, Volume 4, Issue 2, p. 57 –63
- DOI: 10.1049/iet-opt.2009.0011
- Type: Article
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57
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Spectral response (SR) and optical characteristics of GaAs-based heterojunction phototransistors (HPTs) have been successfully predicted for the first time through an advanced absorption model presented in the present article. The model is based on the accurate prediction of photocarriers in the active layers of the phototransistor which, when related to the base current of transistor in forward active mode, enables the prediction of optical characteristics. The importance of collection efficiency in accurate SR modelling is highlighted and it is not considered unity like all the previous studies on HPTs. The layer dependence of the optical power absorption profile at near-bandgap wavelengths is also investigated and its generalisation as a single exponential has been refuted for GaAs-based HPTs. The measured results at 635, 780 and 850 nm show good agreement to the predicted results, validating the proposed theoretical model. - Author(s): H.-H. Chou ; T.D. Wilkinson ; N. Collings ; W.A. Crossland ; H.-T. Chou
- Source: IET Optoelectronics, Volume 4, Issue 2, p. 64 –77
- DOI: 10.1049/iet-opt.2009.0044
- Type: Article
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64
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With an increasing demand on storage devices in network enterprises, storage area networks (SANs) have attracted significant attention and are currently considered as one of the most important network elements in the next generation optical Internet. An optical switch fabric capable of multicast transmission and multiple wavelength operation corresponding to a SAN's growth is critical, since SANs will soon suffer from data bottlenecks and cost inflation because of limited switching capabilities within pure electronics. The authors present and demonstrate a reconfigurable shutter-based free-space optical switching core capable of multicast transmission using multiple wavelengths per-fibre for use in optical SANs. The switch architecture, operation mechanism and the design of key components are described. New optical materials are utilised to raise the switching speed, and ferroelectric liquid crystals (FLCs) or transparent lanthanum-modified lead zirconate titanate (PLZT) have been compared. The optical performance of an implemented crossbar switch prototype is evaluated through a proposed node architecture constructed with a transceiver-based test-bed. - Author(s): M. Karásek ; J. Radil ; J. Vojtěch
- Source: IET Optoelectronics, Volume 4, Issue 2, p. 78 –84
- DOI: 10.1049/iet-opt.2009.0047
- Type: Article
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78
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We present experimental results on transmission of 20 channels over 238 km long link composed of two spans (100 and 138 km) of non-zero dispersion shifted fibre. Transmission is based on distributed Raman amplification. Both spans are counter-directionally pumped by time-division-multiplexed four wavelengths optical units. Five of the 20 channels are 10 GB Ethernet signals (10 GE). Error-free transmission has been checked with 10 GE bit error ratio tester. Experimental results are extended by numerical simulations. - Author(s): K. Nikolaidis and M.J.N. Sibley
- Source: IET Optoelectronics, Volume 4, Issue 2, p. 85 –94
- DOI: 10.1049/iet-opt.2008.0055
- Type: Article
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This study describes a performance analysis of eight different multiple pulse position modulation (PPM) systems with 4, 7, 12, 15, 17, 22, 28 and 33 slots operating over a plastic optical fibre (POF) channel. The receiver/decoder uses slope detection and a maximum likelihood sequence detector (MLSD). As the analysis of any multiple pulse position modulation (MPPM) system is extremely time consuming, especially when the number of slots is large, a software solution was used. A measure of coding quality that accounts for efficiency of coding and bandwidth expansion was applied and original results showed that the middle systems of these MPPM families are the most efficient for a wide range of bandwidths. Although the efficient Gray coding was used for this investigation, a close to optimum mapping is presented for MPPM systems of the families mentioned above. These mappings were found to be superior to the efficient Gray codes, linear coding and a series of random mappings.
Analysis of dynamic encoder and decoder for optical code-division-multiple-access networks
Spectral response modelling of GaAs-based heterojunction phototransistors for short wavelength detection
Implementation of coarse wavelength division multiplexing multi-wavelength routing switch core for storage area networks
Transmission of 20 channels over 238 km of non-zero dispersion shifted fibre using distributed time-division multiplexing-pumped Raman amplification
Investigation of higher order optical multiple pulse position modulation links over a highly dispersive optical channel
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