Interferometric noise
There have been some concerns about the validity of the worst-case
approach that was
taken in our previous document about interferometric noise. In this
document we will extend the previous document in two different ways. In
both approaches worst-case polarization is assumed. In real life the
polarization state will vary slowly with time. However, the polarization
state will persist for a fairly long time and could give random and
unpredictable outages when the polarizations are aligned.
In the first approach, instead of using the worst-case phase between the
main signal and the reflected signal, the BER is averaged over the phase
difference between the interfering signals. Chirp and other dynamic
effects are ignored in this approach. In the second approach a
rate-equation model for a single-mode laser is used, and the resulting
output signal is used to calculate the effect of the interferometric
noise. Here dynamic effects such as chirp and overshoots are taken into
account. Although the semi-analytical approach makes a number of
simplifications it compares fairly well to the more detailed simulated
approach.
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interferometric2.pdf