Performance Characteristics of a Multicore Interferometric Fiber Optic Gyroscope Using a 7-Core Fiber

Abstract

The sensitivity of an interferometric fiber optic gyroscope (IFOG) scales with the length of the sensing optical path. Thus, IFOG development history has seen much work devoted to shrinking ever-increasing lengths of optical fiber into a fixed volume. Indeed, the success of the IFOG as a guidance and navigation technology is founded, to a large extent, on the many advancements in fiber-optics which were required to compact numerous state-of-the-art components – including a multi-kilometer length of optical fiber – to within the size of a teacup.An exciting technology which promises to continue this trend is multicore optical fiber, in which multiple, independent optical waveguides (cores) are placed within the same glass cladding which would ordinarily contain only one core. The dense arrangement of cores in such fibers can be exploited in an IFOG by connecting them in series, and thereby increasing the instrument sensitivity proportionally. As originally proposed by Bergh [1], these features present an opportunity to increase sensitivity while reducing the sensor footprint and simplifying the optical fiber coil - a key driver of cost and complexity in IFOGs.Here we detail performance characteristics of an all-fiber multicore IFOG employing a bend-insensitive, single-mode, 7-core fiber in the sensing coil. Like the recent, first-ever demonstration by Mitani et al. [2], [3], we employ an open-loop testbed architecture with a depolarized sensing loop, in which fiber cores are connected in series via a pair of multicore fan-in/fan-out devices. Here however, the fan-in/fan-out components are tapered fiber devices, packaged in conventional fiber-optic component sleeves, and with the core interconnections made via standard fusion splices [4]. Measurements of noise and long-term stability of the instrument show that its performance is commensurate with the 7X enhanced sensitivity afforded by the optical path length increase. For this 7-core, 154 m long, 10 cm diameter fiber coil, we show long-term gyro bias stability under 0.02 deg/hr and angle random walk of $2.4\, \text{mdeg} /\sqrt {\text{hr}}$. This compares favorably with both noise models and performance measurements in IFOGs of similar scale factor, thus confirming the sensitivity improvement conferred by use of 7-core fiber.The all-fiber configuration of the sensing loop makes this instrument highly practicable as a drop-in replacement for current IFOGs, with no change to existing front-end designs. Moreover, as multicore fiber technology continues to push the frontiers of optical fiber transmission capacity, future designs may benefit from even greater core multiplicity – an exciting prospect for the next generation of compact, low-cost, high-accuracy IFOGs.