Interferometric Fiber Optic Gyroscope Research Articles

Tightly Coupled IFOG-Based GPS Guidance Package

An interferometric fiber-optic gyroscope (IFOG)-based GPS Guidance Package (GGP) achieved 4 m spherical error probable (SEP) in an integrated GPS/inertial mode and 10 m error growth after 5 min without GPS reception under harsh field conditions. The 295 in 3 , 14 lb Phase 1 GGP systems were evaluated under controlled laboratory conditions and during van testing, as well as in a U.S. Army Fire Support Team Vehicle (FISTV). During the FISTV demonstration, the GGP significantly outperformed the Army's currently used equipment. The results of these tests validated the tightly coupled GPS/inertial design approach with fiber-optic sensors and the system's suitability for applications with demanding environmental requirements. Current development is focused on 0.8 nmi/h inertial performance and miniaturization of the system to a 100 in 3 , 7 lb package. The Phase 2 design provides capabilities of high dynamics and low jamming susceptibility, as well as adaptability to multiple military and commercial applications with a low-cost production system.

Configuration to double I-FOG output power: Experimental investigation of noise performance and temperature effect

We propose a novel interferometric fiber-optic gyroscope (I-FOG) which has an improved signal to noise ratio in rotation measurement. The basic idea of this I-FOG is to use an additional polarization so that all the optical power from the light source can be utilized. The performance of this fiber gyro is experimentally examined, which shows that the noise level of rotation rate is almost half lower than that of a conventional I-FOG. In addition, the temperature effects on rotation measurement are also investigated. It shows that in the optimal case of 90/spl deg/ alignment between two polarizer axes the long-term drift of this fiber gyro can be greatly suppressed, and the drift can be suppressed to a comparable level as that of the conventional I-FOG only if the polarization properties of the fiber, coupler and polarizers are improved beyond those normally achieved.

Proton‐induced degradation in interferometric fiber optic gyroscopes

Recent advances in Interferometric Fiber Optic Gyroscope (IFOG) technology have enabled these devices to equal, and in some respects exceed, the performance of the floated, spinning wheel rate integrating gyroscope. However, their ability to perform in a space radiation environment has been a significant concern. Test results are presented addressing the effects of space radiation on the performance of a high precision pointing grade IFOG. Proton-induced degradation of the optical components of an IFOG is evaluated based on testing performed at the Harvard Cyclotron Laboratory (HCL). Rationale is provided for using the HCL proton accelerator as a reasonable simulation of the space environment. An analysis is presented which prioritizes the component-level dose tests based on expected radiation sensitivities. The evaluation addresses both total dose (to about 12 krad) and dose rate effects. Testing was performed at the component level as well as the system level with an expanded version of a closed-loop operational IFOG. Primary concerns include permanent attenuation and spectral transmission (wavelength) sensitivity to total dose, and angle random walk and bias stability degradation as a function of dose rate. Component level results are presented for a superfluorescent light source, integrated optics chip (IOC), coupler, and polarization maintaining fiber coils. Closed-loop transient noise results are evaluated based on dose rate testing of the IOC, coupler, and fiber coil.

New interferometric fiber-optic gyroscope with amplified optical feedback

A novel interferometric fiber-optic gyroscope with amplified optical feedback by an Er-doped fiber amplifier (EDFA) is proposed and theoretically investigated (the proposed gyroscope is named the feedback EDFA-FOG, FE-FOG in what follows). The FE-FOG functions like a resonant fiber-optic gyro (R-FOG) because of its multiple utilization of the Sagnac loop; however, it is completely different because a low-coherence light source is used. In addition, the gyro output signal is pulsed because the modulation frequency of the phase modulator placed in the Sagnac loop is selected to match the total round-trip time delay of the light, which includes the Sagnac-loop delay plus that of the feedback loop of the fiber amplifier. The sharpness of the output pulse can be adjusted by both the gain of an EDFA and the modulation depth of the phase modulator. When rotation occurs the peak position of the output pulse is shifted as a result of the Sagnac effect. The resolution of the rotation measurement depends on the sharpness of the output pulse. The techniques of both the open-loop and closed-loop methods are described in detail, which shows the great advantage of the proposed gyroscope over the to the conventional interferometric fiber-optical gyroscope (I-FOG).

Open Loop Fiber Optic Gyroscope : A Technical Note

This technical note describes the design and fabrication of a prototype open-loop interferometric fiber-optic gyroscope (IFOG). The gyro transfer function is transposed from that of a raised-cosine to a sine function using AC modulation, giving maximum sensitivity at rest. Among various signal processing methods, lock-in principle is used to detect the Sagnac phase shift due to rotation. Initial work is done with bulk-optic components. Finally, all-fiber gyroscope is built using laser diode (1300 nm), PINFET detector, fiber couplers and PZT phase modulator. An effort is made to develop compact IFOG with sensing coil diameter of 10 cm and signal processing card of size 10 x 6.5 sq cm. The present set-up is able to detect the direction of rotation at a rotation rate of 5 x 10/sup -4/ radian per second. Presently, the performance of the set-up is limited by the difficulty in achieving complete reciprocity.

Error of rotation output due to light injection to LD source in a self‐coupled interferometric fiber GYRO: Experiment

AbstractAn experiment regarding an inexpensive self‐coupled interferometric fiber optic gyroscope (self‐coupled I‐FOG) is conducted. The gyro output and rotation‐rate resolution of a self‐coupled I‐FOG are investigated and compared with those of a conventional I‐FOG having two couplers. The error effect of rotation output in a self‐coupled I‐FOG due to the interaction of the gyro output and the laser source is examined. Our results show that the resolution of rotation rate of an economical self‐coupled I‐FOG is one order of magnitude lower than that of a conventional I‐FOG. © 1995 John Wiley & Sons, Inc.

Interferometric fiber-optic gyroscope performance owing to temperature-induced index fluctuations in the fiber: effect on bias modulation

An analysis of the noise floor owing to temperature-induced index fluctuations in the fiber of a dynamically biased interferometric fiber-optic gyroscope is presented. A comparison with shot noise indicates that, for a harmonic bias modulation, thermal noise in the fiber dominates for fiber lengths longer than ~1-2 km when practical source power levels are considered. The noise can be reduced or eliminated by the proper choice of modulation frequency or waveform.

FIBER-OPTIC GYROSCOPES FOR AUTOMOTIVE APPLICATIONS

We review recent developments in interferometric fiber-optic gyroscopes for automotive applications. These gyroscopes use only elliptical-jacket or elliptical-core polarization-maintaining fibers to make their optical systems immune to environmental effects, and all of them use open-loop phase-modulation signal processing circuitry. We have begun mass-production of a gyroscope for automotive navigation and location systems. Another gyroscope employing an application specific integrated circuit developed for reducing size, cost and power consumption outputs the rotation rate as an analog voltage, and can be used for automotive chassis control and navigation systems. A more accurate gyroscope and a three-axis FOG system combined with clinometers can be applied to motion measurement systems for chassis development and testing. For further enhancement in terms of size, cost, and accuracy, we have developed an integrated optical circuit and a gyroscope that uses it.

Theory of a novel high sensitivity optical fibre gyroscope

A novel optical fibre gyroscope, with a structure making use of the combination of a Sagnac interferometer with an active fibre ring-resonator, is proposed and analysed. It can be regarded as a generalised structure of the conventional Sagnac interferometric fibre optic gyroscope (SIFOG). Counter-propagating optical waves in the gyroscope can circulate many times in the sensing loop into which an optical amplifier is incorporated to compensate partially for optical losses of each circulation. The optical response is effectively the sum of the optical responses of a series of conventional Sagnac interferometric fibre optic gyroscopes having effective loop length equal to the fibre loop length multiplied by the number of circulations. We show that the sensitivity of the proposed gyroscope can be two orders of magnitude higher than that for a conventional SIFOG and that the minimum detectable nonreciprocal phase shift limited by the amplifier noise is nearly one order of magnitude smaller than that of conventional SIFOG limited by quantum noise. These performance enhancements cannot be obtained by incorporating an optical amplifier into the conventional SIFOG structure.

Amplified fiber ring resonator gyro

The sensitivity of a fiber-optic ring resonator gyro increases with increasing resonator finesse, which can be achieved by including a fiber amplifier in the ring. The spontaneous emission from a fiber amplifier introduces additional noise. The effect of this noise on the performance of an amplified fiber ring resonator gyro (ARRG) is theoretically investigated, assuming an infinity source coherence length. It is found that for a given fiber length, the uncertainty in measuring the rotation rate with an ARRG can be more than one order of magnitude lower than with a shot noise limited passive ring resonator gyro (PRRG), and about three orders of magnitude lower than with an interferometric fiber optic gyro (IFOG). >

Novel fibre optic gyroscope with a configuration combining Sagnac interferometer with fibre ring resonator

A novel fibre optic gyroscope, with a structure making use of the combination of a Sagnac interferometer with an active fibre ring-resonator, is proposed and analysed. The proposed gyroscope can be viewed as a generalised structure of the conventional Sagnac interferometric type fibre optic gyroscope. It has the advantages of both long fibre loop length and multipath interferences. By inserting a fibre amplifier in the loop to provide an optical gain of several dB, the relative maximum sensitivity is enhanced to ~30 times more than that of conventional Sagnac interferometric fibre optic gyroscopes.

Excess noise in fiber gyroscope sources

Excess noise was measured in three potential interferometric fiber gyroscope sources, superluminescent diodes at 0.83 and 1.3 mu m, and a superfluorescent fiber source at 1.06 mu m. All three sources showed limiting signal-to-noise ratios in the 128-132 dB range (1 Hz bandwidth at 100 kHz), in agreement with their measured linewidths. The impact of the excess noise on the fiber gyro random walk coefficient is shown. It is pointed out that the noise source considered is important for interferometric fiber optic gyros because it imposes a limitation that does not arise in optical gyros which use narrowband sources. >

A comparison of the radiation vulnerabilities of ring resonator and interferometric fiber optic gyroscopes

A comparison is made between passive ring-resonator and interferometric fiber-optic gyroscope sensitivity to the radiation darkening of optical fibers. The radiation degradation factor for each type of gyroscope is developed, and figures of merit are given for comparing gyroscopes independently of the specific mechanization or modulation scheme used. It is shown that for most practical situations, interferometric gyros offer superior performance in radiation environments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>