Fiber optic gyroscope based inertial sensors are being used within increasingly severe environments, enabling unmanned systems to sense and navigate in areas where GPS satellite navigation is unavailable or jammed. A need exists for smaller, lighter, lower power inertial sensors for the most demanding land, sea, air, and space applications. <p> </p>Fibernetics is developing a family of inertial sensor systems based on our closed-loop navigation-grade fiber optic gyroscope (FOG). We are making use of the packaging flexibility of the fiber to create a navigation grade inertial measurement unit (IMU) (3 gyroscopes and 3 accelerometers) that has a volume of 102 cubic inches. We are also planning a gyrocompass and an inertial navigation system (INS) having roughly the same size. In this paper we provide an update on our development progress and describe our modulation scheme for the Sagnac interferometers. We also present a novel multiplexed design that efficiently delivers source light to each of the three detectors. In our future development section we discuss our work to improve FOG performance per unit volume, specifically detailing our focus in utilizing a multicore optical fiber.
We describe amplitude-type polarization errors in depolarized fiber gyros and show a management scheme for their suppression. Prototypes operating both at 0.8 micrometers and 1.3 micrometers wavelengths exhibiting navigation grade drift and noise performance have been realized.
Signal transformations around an open-loop fiber gyroscope are identified. This shows that the interferometer performs a derivative. An electronic integrator is used to cancel this effect. Control theory shows that a second integrator can then be used to complete the closed-loop architecture. Variations of this architecture are used by both dual-ramp and serrodyne approaches. The method that these two techniques use to manage the second integrator, and avoid saturation of its output, is described.