Abstract
The major drawback of incoherent broadband sources (BBSs) is their
inherent intensity noise. Semiconductor optical amplifiers (SOAs) can be
exploited at the transmitter to mitigate this noise. Optical filtering at
the receiver, however, leads to the return of most of suppressed noise.
Wider filtering at the receiver is the best known strategy to maintain
performance gains, at the price of reduced spectral efficiency due to the
tradeoff between noise cleaning and adjacent channel crosstalk. We introduce
a novel balanced receiver for wavelength division multiplexing (WDM) systems
that maintains greater noise cleaning and leaves spectral efficiency
unchanged. Unlike standard receivers, our balanced scheme does not filter
the desired signal. In this paper, we first demonstrate that the newly
proposed receiver is equivalent to standard WDM receivers when no SOA for
noise cleaning is present at the transmitter. Although a 2.9-dB power
penalty is incurred, network capacity is unchanged, i.e., bit error rate
(BER) floors due to intensity noise are the same. When SOAs are employed to
mitigate severe intensity noise, we show that our receiver outperforms the
wide filtering strategy by two orders of magnitude. Dense WDM capacity is
demonstrated up to 10 Gb/s using a
thermal source, a saturated SOA, and the balanced detection scheme. A BER of $10^{-6}$ is achieved at 10 Gb/s;
further improvement is possible using low overhead forward error correction
or a better SOA design. This demonstrates the ability of spectrum-sliced
wavelength division multiplexing (SS-WDM) passive optical networks (PONs) to
operate at 10 Gb/s at good spectral efficiency. Error performance better
than $10^{-9}$ is achieved up to 8 Gb/s with 30-GHz optical channel bandwidth
and 100-GHz spacing.
© 2009 IEEE
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