technology photodiodes
slow minority carrier injection process, which severely degrades the modulation speed and limits the maximum data transmission rate. By use of the ultra-fast switching characteristic of the NBUTC-PD, we have demonstrated the photonic-transmitter-mixer for an MMW-over-fibre communication system operating at 20 Gbit/s (see Figure 6).
In such proposed scheme, it is possible to use another optical wavelength to provide the data signal for bias modulation on our photonic-transmitter-mixer, by converting this to electrical 20 Gbit/s data with another low-speed photo-diode.
Getting commercial traction Today, the biggest opportunities for MMW wireless linkage in consumer electronics exist at 60 GHz, for indoor linking, and at 100 GHz, for outdoor linking. Applications include wireless HDMI broadcasting and linking, and high-speed data transfer between cell phones and Sony’s cyber-shot camera via Transfer Jet, a proximity-based, wireless technology that can transfer images, video, and other files between compatible devices held about an inch apart.
Up until now, photonic technology has not made an impact on these systems. Competition from the all- electronic approach is strong, and the cost of the MMW photonic wireless linking approach must fall. This situation could change, because increasing maturity of CMOS IC technology is making it possible to install MMW CMOS local-oscillator (LO) chips at each base station without using a synchronized LO signal.
However, the MMW wave that is produced above 60 GHz behaves like an optical-wave: Propagation of the signal is in a straight line, and obstacles in the way drive down its intensity. Realising good network
Figure 6.(a) The photonic-transmitter-mixer developed by National Central University,Taiwan,that is used in the last-mile MMW-over-fibre system; and (b) set-up of a photonic wireless linking system for 20Gbit/s data transmission using a line-by-line pulse shaper with a central frequency around 100 GHz as the photonic MMW source
coverage for the end-user could require the deployment of numerous remote antenna units, particularly for an outdoor wireless linking system.
The biggest advantage of the photonic technique over the all-electronic approach is the use of a fibre backbone to interconnect and synchronize the units. This minimizes interference and multi-path effects between the units. Other merits of the photonic technology include superior immunity to bad weather conditions, plus an improvement in data processing efficiency. However, these benefits will not be enjoyed unless there is widespread availability of ultra-high speed photodiodes and photonic-transmitter (mixer) modules.
© 2012 Angel Business Communications. Permission required.
Further reading
Figure 5.(a) An end-fire quasi-yagi antenna for rectangular waveguide (WR) excitation; (b) top- view of an NBUTC-PD based photonic transmitter with an integrated quasi-yagi antenna for WR-10 waveguide excitation; and (c) the device during measurement
M. Lazarus, IEEE Spectrum 47 26 (2010) J.-W. Shi et. al. NPG Asia Materials 3 41 (2011) H.-J. Song et. al. IEEE Trans. Terahertz Science Tech. 1 256 (2011) Nan-Wei Chen et. al. IEEE Trans. Microwave Theory Tech. 59 978 (2011) H. Ito, et. al. IEEE J. of Sel. Topics in Quantum Electronics 10 709 (2004) F.-M. Kuo et. al. IEEE/OSA Journal of Lightwave Technology 29 432 (2011) F.-M. Kuo et. al. IEEE Photonics Journal 3 209 (2011)
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