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Optical mm-Wave Synthesizer Using Semiconductor Ring Laser (a Review)

100%
Memon M., Siraj M., Fathallah H.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1274-1276
EN
Millimeter wave (mm-wave) technology is significant for military needs and applications due to its numerous advantages, such as huge bandwidth, deploying small antenna and high radar resolution. Due to atmospheric influence, mm-wave is important in short-range applications such as fire control radar. Similarly for the next-generation communication and military applications, high-speed radio over fiber networks are very crucial. In this paper, a review of the generation and modulation of millimeter-wave signal optically using semiconductor ring laser (SRL) has been done. The phenomena of optical injection locking and four-wave mixing are exploited in SRL to generate radio frequency (RF) optical signals. The signals with huge data rate can be transferred directly from an intensity modulated optical signal onto a RF optical signal with RF frequency tunable in steps of the free spectrum range (FSR) of SRL. They can be converted with flexible RF modulation formats over the optical carrier.
2
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Radio Frequency Generator Using Four Wave Mixing in Cascaded Nonlinear Semiconductor Optical Amplifiers

100%
Memon M., Siraj M., Fathallah H., Khan M.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 4
832-834
EN
For the last three decades, the phenomenon of four-wave mixing is a significant technique for generation of light at new distinct wavelength. When two distinct laser beams (pump and probe) beat together in a non-linear medium, few modes are increased in the power at same distance from the probe and pump, as a result of four-wave mixing. In this paper, cascading structure of two semiconductor optical amplifiers produces very strong four-wave mixing. This technique is exploited to devise a tunable radio frequency signal generator. The wavelength distance between pump and probe laser beams determines the radio frequency of the generated signal. Using this scheme, it can be observed from the experimental results, that there is an increase of more than 3 dB in signal to noise ratio at 7 Gbits/sec data rate of the 60 GHz generated mm-wave signal. Moreover, the radio frequency can be tuned to hundreds of GHz by varying the distance between the pump and probe signals. This scheme will readily serve as future all optical radars. It is also a key technique for short-range communication systems for military applications. The above scheme can also be monolithically integrated.
3
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Video on Demand Over Optical Wireless Communication Links

100%
Siraj M., Memon M., Khan M.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 4
826-828
EN
Video on demand technology is a modern wireless communication application which requires a large bandwidth. Optical wireless networks, as a potential alternative to radio frequency, is an emerging technology that is easier to set up and provides a cost effective solution, where a physical network is difficult to deploy. Optical wireless networks can be used as a backbone to provide the much needed bandwidth for video on demand application. In this paper, Wavelength Division Multiplexing modulation scheme is proposed for the optical wireless networks due to its significance of transmitting distinct data channels at different wavelengths. Wavelength Division Multiplexing can be easily integrated with optical wireless networks, consequently resulting in an increased data rate. This paper presents a novel approach of integrating video on demand with the state of art Wavelength Division Multiplexing based optical wireless networks. Furthermore, the paper discusses the challenges and advantages over the convention modulation schemes.
4
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Performance Enhancement of Telemedicine Network by Free Space Optics Links Provisioning

100%
Siraj M., Shoaib M., Memon I.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 1
43-45
EN
Health care has benefited immensely with the implementation of fast moving information technology. It is a challenging assignment for the researchers to implement the present day technologies such as wireless mesh networks. Wireless mesh networks are deployed to guarantee a reliable and stable network infrastructure backbone to telemedicine systems. They are preferred to other wireless networks, as the solution which they provide is robust for broadband services. They are robust because if routing is not possible due to some mesh nodes failure, routing can be done by the other mesh nodes present. Wireless mesh network cannot only spread coverage but also save both cabling cost and human resource. However, their performance is degraded due to interference and varying load. Interference is a critical issue in wireless mesh networks. The interference occurs because of the congested unlicensed radio frequency spectrum. This problem can be addressed by applying free space optics technology for transmission instead of radio frequency technology in the unlicensed spectrum. Network capacity issue is addressed by provisioning free space optics links to generate the much needed throughput and to minimize interference. Telemedicine network is a network, which requires a high capacity bandwidth to cater for a large number of remote patients. It is observed that free space optics links provisioning results in a significant performance enhancement for the telemedicine network.
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