Fogphotonics products instruction

Y-integrated optic chips

Lithium niobate-based Y junction waveguide multifunction integrated optic chip (M-IOC) is one of core optic components in fiber optic gyro. Its performances have very important influences on fiber optic gyro (FOG) accuracies. Fully understanding its performances in FOG will help us to further improve fiber optic gyro performance (bias drift < 0.01 degrees/h). Fogphotonics focuses on the researching of application features of Y-junction integrated optic chip(Y-IOC) in FOG with bias drift less than 0.01 degrees/h It also describes the system test methods for checking integrated optic chip performances. Interesting research points are: Y-IOC optic technology and its application in FOG, features of Y-IOC in FOG, the corresponding test system and the matching of Y-IOC with FOG system. Research results show: Y-IOC optic performances, Y-IOC electrical characteristics, as well as the matching between electrical circuits of FOG system and electrical features of Lithium niobate-based Y junction waveguide multifunction integrated optic chip all together play very important roles in achieving high performances of FOG.

http://www.fogphotonics.com/Pros_View.aspx?classId=47&id=244

Ring Laser Gyros (RLG)

Main article: Ring laser gyro

A ring laser gyro splits a beam of laser light into two beams in opposite directions through narrow tunnels in a closed optical circular path around the perimeter of a triangular block of temperature-stable Cervit glass with reflecting mirrors placed in each corner. When the gyro is rotating at some angular rate, the distance traveled by each beam becomes different—the shorter path being opposite to the rotation. The phase-shift between the two beams can be measured by an interferometer, and is proportional to the rate of rotation (Sagnac effect).

In practice, at low rotation rates the output frequency can drop to zero after the result of backscattering causing the beams to synchronise and lock together. This is known as a lock-in, or laser-lock. The result is that there is no change in the interference pattern, and therefore no measurement change.

To unlock the counter-rotating light beams, laser gyros either have independent light paths for the two directions (usually in fiber optic gyros), or the laser gyro is mounted on a piezo-electric dither motor that rapidly vibrates the laser ring back and forth about its input axis through the lock-in region to decouple the light waves.

The shaker is the most accurate, because both light beams use exactly the same path. Thus laser gyros retain moving parts, but they do not move as far.

http://www.fogphotonics.com/Pros_View.aspx?classId=104&id=269

Fiber optic gyros (FOG)

Main article: Fiber optic gyroscope

A more recent variation on this, the fiber optic gyroscope, uses an external laser and two beams going opposite directions (counter-propagating)in long spools (several kilometers) of fiber optic cable, with the phase difference of the two beams compared after their travel through the spools of fiber.

The basic mechanism, monochromatic laser light travelling in opposite paths, and the Sagnac effect, is the same in a FOG and a RLG, but the engineering details are substantially different compared to earlier laser gyros.

Precise winding of the fiber-optic coil is required to ensure the paths taken by the light in opposite directions is as similar as possible. The FOG requires more complex calibrations than a Laser ring gyro making the development and manufacture of FOG's more technically challenging that for a RLG. However FOG's do not suffer from laser lock at low speeds and do not need to contain any moving parts, increasing the maximum potential accuracy and lifespan of a FOG over an equivalent RLG.

http://www.fogphotonics.com/Pros_View.aspx?classId=48&id=177