Abstract
We demonstrate through theoretical analysis that unlike predicted by
others, an unbiased coupled resonant optical waveguide (CROW) gyroscope made
of $N$ ring resonators
has a response to a rotation rate $\Omega$ that is proportional to $(N
\Omega)^2$, and hence its sensitivity to small rotation rates
is vanishingly small. We further establish that when proper phase bias is
applied to the CROW gyro, this response becomes proportional to $N\Omega$ and the sensitivity to small rotation rates
is then considerably larger. However, even after optimizing the CROW parameters
($N$ and the ring-to-ring
coupling coefficient $\kappa$),
the CROW gyro has about the same sensitivity as a conventional fiber optic
gyroscope (FOG) with the same loop loss, detected power, and footprint. This
maximum sensitivity is achieved for $N
= 1$, i.e., when the CROW gyro resembles a resonant FOG. The
only benefit of a CROW gyro is therefore that it requires a much shorter length
of fiber, by a factor of about $1/ (2 \kappa)$, but at the expense of a stringent control of the rings' optical
path lengths, as in a resonant FOG. Finally, we show that the slower apparent
group velocity of light in a CROW gyro compared to a FOG is unrelated to this
shorter length requirement.
© 2009 IEEE
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