First I have heard of it but, it looks like that could be the wave of the future for some airplanes.
According to an article I am reading about a new Embraer business jet, has Northrop Grumman LITEF LCR-100 fiber optic gyros that are private labeled as Rockwell-Collins AHS-40000 units(not sure what the privaye labeling means).
These units provide virtually all the inertial position, attitude Heading/Reference, and velocity outputs of top end laser IRS boxes., but at a much lower cost and weight. The 6 lb. units have a lower than 12 nm/hour drift rate, require no forced air cooling, and have a 15,000 hour MTBF.
The article does mention that there is an optional Honeywell LaserRef box that improves navigation performance in remote and oceanic regions by eliminating the need for GPS RAIM checks for dispatch and by prolonging the period during which the aircraft can maintain navigation performance without GPS or VOR/DME updates.
So perhaps the fiber optic gyro units could become more common on short/medium haul aircraft. The CRJ 1000 has approval for this.
From Wikipedia....
"A
fibre optic gyroscope (
FOG) senses changes in orientation using the
Sagnac effect, thus performing the function of a mechanical
gyroscope. However its principle of operation is instead based on the
interference of light which has passed through a coil of
optical fibre, which can be as long as 5 km. Two beams from a laser are injected into the same fibre but in opposite directions. Due to the
Sagnac effect, the beam travelling against the rotation experiences a slightly shorter path delay than the other beam. The resulting differential
phase shift is measured through interferometry, thus translating one component of the
angular velocity into a shift of the interference pattern which is measured
photometrically.
From Rockwell-Collins...."The Collins Aerospace AHS-4000 Attitude and Heading Reference System (AHRS) features a distinctive solid-state design in a small, lightweight package. The embedded low-power fiber-optic gyro and triple-axis MEMS accelerometers ensure high reliability and low power consumption. Continuous monitoring of all functions and internal diagnostics gives you a high-integrity system. You can operate the AHS-4000 in several modes to provide your aircraft with the most accurate navigation data based on available inputs. After self-aligning, the system operates like an Inertial Reference System, providing free inertial navigation position and velocity outputs along with the basic AHRS functions. For higher precision calculations, the AHS-4000 can use GPS inputs."
The fiber optic may be very long but it is not straigh. It has thousands of turns(coiled) with the more turns, the better it is.
Any additional info would be welcome.