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Cheng Gao
Room 410, 4th Floor, Kevin St

M.Sc. in Electronics, B.Eng in Applied Physics

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Postgraduate student (Ph.D.) Full-time


Techniques for bi-directional optical transmission over a single plastic optical fibre

The objective of Cheng’s research is to investigate the issues involved in bi-directional optical transmission system utilising graded index plastic optical fiber (GI-POF). The distances involved are less than 100 m, the maximum distance found in horizontal connections in local area networks and other short-range automotive and aeronautical applications. The bit rate target is at least 622 Mbits/sec in each direction.

A novel bi-directional optical coupling technique for transmission between a transceiver and a single POF have been proposed. An angle-terminated method on POF end has been investigated to realize the bi-directional coupling technique. The investigation shows that the numerical aperture of POF increases with the degree of the tilt termination. The results have been published in the proceeding of SPIE – the International Society for Optical Engineering, regional meeting, Ireland, 2002 [1].

The level of the Rayleigh backscattering within POF reduces the signal-to-noise ratio by causing cross-talk to the local receiver from the local transmitter. The Rayleigh backscattering within POF has been investigated and modelled. A theoretical analysis shown that the total Rayleigh backscattering increases with the fiber length and it also decreases with the increase of the wavelength of the light. The results have been published in 8th high-frequency colloquium, Belfast, Northern-Ireland [2].


[1] C. Gao, G. Farrell, “Numerical aperture characteristic of angle-ended plastic optical fiber”, Proceedings of Opto Ireland, SPIE regional meeting, Galway, Ireland, 2002.

[2] C. Gao, G. Farrell, “Modelling of Rayleigh backscattering on plastic optical fiber”, Digest in 8th high-frequency postgraduate student colloquium, IEEE UK and Ireland section, Belfast, Northern Ireland, 2003.

Laboratory Responsibilities

Optical Communications, FT-221, - Honours degree in electrical/electronic engineering, 4th year.

Circuit Theory, DT 273 2P – Diploma in Applied Science, Year 2, Applied physics option.



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