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Power efficient optical OFDM J. Armstrong and A.J. Lowery

Summary: Power efficient optical OFDM
J. Armstrong and A.J. Lowery
A new technique for using orthogonal frequency division multiplexing
(OFDM) in optical systems is presented. Clipped OFDM is derived
from a bipolar OFDM waveform by setting the negative values to zero.
It has an optical efficiency 8 dB better than DC biased OFDM. If only
the odd OFDM subcarriers are modulated, the clipping noise is
orthogonal to the wanted signal.
Introduction: Orthogonal frequency division multiplexing (OFDM)
allows high-speed data transmission across a dispersive channel, so is
used in many new and emerging high-speed wired and wireless
communication systems. However, OFDM is not used in commercial
optical communication systems. This is because OFDM signals are
bipolar, while in optical systems that use intensity modulation (IM),
only unipolar signals can be transmitted. A large DC bias is usually
added to OFDM signals requiring a high mean optical power with a
low modulation depth. This is very inefficient. We show how optically
power efficient OFDM signals can be designed. We describe the new
technique applied to a baseband signal, but it is also applicable to
passband signals.


Source: Armstrong, Jean - Department of Electrical and Computer Systems Engineering, Monash University


Collections: Engineering