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Design and Development of Fiber Optic Gyroscopes
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Book Description

Realizing the potential of the fiber optic gyro, like the ring laser gyro, has been a long and expensive process. Many researchers have made important enabling contributions, and many more engineers have worked diligently for many years on solving the problems associated with realizing viable inertial navigation and guidance produce at affordable costs. This book arose from efforts to form a special session to commemorate the fortieth anniversary of the first hardware demonstration of the fiber gyro in 1976 by Vali and Shorthill. The chapters include contributions from key engineers and scientists who have worked from as early as 1977 to the present on manufacturing high-performance fiber gyros for many applications.

Book Details

Date Published: 31 July 2019
Pages: 304
ISBN: 9781510626096
Volume: PM303

Table of Contents
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Table of Contents

1 A Potpourri of Comments about the Fiber Optic Gyro for Its Fortieth Anniversary: How Fascinating It Was and Still Is!
Hervé C. Lefèvre
1.1 Introduction
1.2 Historical Context of the Sagnac-Laue Effect
1.3 Fascinating Serendipity of the Fiber Optic Gyro
     1.3.1 The proper frequency
     1.3.2 Perfection of the digital phase ramp
     1.3.3 The optical Kerr effect
     1.3.4 Technological serendipity: erbium ASE fiber source and proton-exchanged LiNbO3 integrated-optic circuit
1.4 Potpourri of Comments
     1.4.1 OCDP using an OSA
     1.4.2 Strain-induced "T dot" Shupe effect
     1.4.3 Transverse magneto-optic effect
     1.4.4 RIN compensation
     1.4.5 Fundamental mode of an integrated-optic waveguide
     1.4.6 Limit of the rejection of stray light in a proton-exchanged LiNbO3 circuit with absorbing grooves
1.5 Conclusion
Acknowledgment
References

2 The Early History of the Closed-Loop Fiber Optic Gyro and Derivative Sensors at McDonnell Douglas, Blue Road Research, and Columbia Gorge Research
Eric Udd
2.1 Introduction
2.2 Invention and Demonstration of the Closed-Loop Fiber Gyro
2.3 Looking for Error Sources, Finding New Sensors
2.4 A Flow of Ideas
2.5 Moving into Viable Products and Applications
2.6 Summary and Conclusions
Acknowledgments
References

3 20 Years of KVH Fiber Optic Gyro Technology: The Evolution from Large, Low-Performance FOGs to Compact, Precise FOGs and FOG–Based Inertial Systems
Jay Napoli
3.1 Introduction
3.2 Superior Performance through End-to-End Manufacturing
     3.2.1 At the heart of the FOG: creating the fiber
     3.2.2 The core design of KVH open-loop FOGs
     3.2.3 Design advantages
     3.2.4 Key gyro performance factors
3.3 Evolution of the Technology
     3.3.1 The creation of D-shaped, elliptical-core fiber
     3.3.2 The first generation of KVH FOGs
     3.3.3 The shift to digital signal processing
     3.3.4 Changing the game: the invention of ThinFiber
     3.3.5 Expanding capabilities with high-performance fully integrated systems
3.4 Setting the Course for the Future of FOG Technology and Expanded Applications
     3.4.1 Navigation and control
     3.4.2 Positioning and imaging
     3.4.3 Stabilization and orientation
     3.4.4 Looking ahead

4 Fiber Optic Gyro Development at Honeywell
Glen A. Sanders, Steven J. Sanders, Lee K. Strandjord, Tiequn Qiu, Jianfeng Wu, Marc Smiciklas, Derek Mead, Sorin Mosor, Alejo Arrizon, Waymon Ho, Mary Salit, Neil A. Krueger, Clarence Laskoskie, Chellappan Narayanan, and Wes Williams
4.1 Introduction
4.2 IFOG Status
     4.2.1 Navigation-plus-grade IFOGs
     4.2.2 Strategic-grade IFOGs
     4.2.3 Reference-grade IFOGs
4.3 RFOG Development
     4.3.1 New RFOG architecture
     4.3.2 RFOG experimental results
     4.3.3 RFOG component development and future implementation
4.4 Summary
References
5 Fiber Optic Gyros from Research to Production
George A. Pavlath
5.1 Abstract
5.2 Research
5.3 Development
5.4 Productionization
5.5 Summary
References
6 Technological Advancements at Al Cielo Inertial Solutions
Meir Rosilio, Lisa Koenigsberg, Noam Pasternak, and Arnon Arbel
6.1 Introduction
6.2 Standard Control Loop
     6.2.1 Control model
     6.2.2 Sub-specifications and verifications
     6.2.3 Navigation accuracy sub-specification
     6.2.4 Monte Carlo simulation
     6.2.5 HITL simulation
6.3 Optimized Control Loop
     6.3.1 Control block
     6.3.2 Monte Carlo simulation
     6.3.3 HITL results
6.4 Inertial Measurements
6.5 Conclusion
Acknowledgement
References
7 Current Status of Fiber Optic Gyro Efforts for Space Applications in Japan
Shinji Mitani, Tadahito Mizutani, and Shin-ichiro Sakai
7.1 Current Status of FOGs for Space Applications
7.2 Activities for Improving Coil Performance
     7.2.1 Symmetrical winding
     7.2.2 Thermal conductivity and strain attenuation
     7.2.3 Zero-sensitivity winding design
     7.2.4 Summary of activity results
7.3 Conclusion
Acknowledgement
References

8 Fiber Optic Gyro Development at Fibernetics
Ralph A. Bergh
8.1 Introduction and Past Development
8.2 Current Development
8.3 Basic FOG Design
8.4 Dual-Ramp Phase Modulation
     8.4.1 Low-frequency approach
     8.4.2 High-frequency approach
8.5 Three-Axis Source-Sharing Design
8.6 Future Development
     8.6.1 Multicore fiber
8.7 Summary
References
9 Recent Developments in Laser-Driven and Hollow-Core Fiber Optic Gyroscopes
M. J. F. Digonnet and J. N. Chamoun
9.1 Introduction
9.2 Backscattering Errors in a Laser-Driven FOG
9.3 Polarization-Coupling Errors in a Laser-Driven FOG
9.4 Kerr-Induced Drift in a Laser-Driven FOG
9.5 Techniques for Broadening the Laser Linewidth
     9.5.1 Linewidth broadening through optimization of the laser drive current
     9.5.2 Linewidth broadening through external phase modulation
          9.5.2.1 Principle and advantages
          9.5.2.2 Linewidth broadening using sinusoidal modulation
          9.5.2.3 Linewidth broadening using pseudo-random bit sequence modulation
          9.5.2.4 Linewidth broadening using a Gaussian white noise modulation
     9.5.3 Measured dependence of noise and drift on laser linewidth
9.6 Hollow-Core Fiber Optic Gyroscope
     9.6.1 Kerr-induced drift
     9.6.2 Shupe effect
     9.6.3 Faraday-induced drift
     9.6.4 Noise and drift performance of HCF FOGs
9.7 Conclusions
References

10 Optical Fibers for Fiber Optic Gyroscopes
Chris Emslie
10.1 Introduction
10.2 Coil Fibers
     10.2.1 Stress- and form-birefringent fiber types
          10.2.1.1 Elliptical-core form-birefringent fiber
          10.2.1.2 Bow-tie fibers
          10.2.1.3 PANDA fiber
          10.2.1.4 Elliptical-jacket fiber
          10.2.1.5 Elliptical-core, form-birefringent fiber
     10.2.2 Microstructures in hollow-core, photonic bandgap fibers
          10.2.2.1 Bandgap fiber fabrication
     10.2.3 Multicore fiber
          10.2.3.1 Fabrication
10.3 Coil Fiber Design Considerations
     10.3.1 Diameter
     10.3.2 Wavelength
     10.3.3 Attenuation
     10.3.4 Polarized versus depolarized design
     10.3.5 Birefringence
     10.3.6 Numerical aperture
     10.3.7 Coating package design
     10.3.8 Radiation tolerance
10.4 Component Fibers
     10.4.1 ASE sources
     10.4.2 PM splitters and couplers
     10.4.3 Polarizing fibers
10.5 Epilogue
References

11 Techniques to Ensure High-Quality Fiber Optic Gyro Coil Production
X. Steve Yao
11.1 Introduction
11.2 Static Performance Parameters and Testing Methods
     11.2.1 Polarization-maintaining fiber coils
          11.2.1.1 Insertion loss and polarization extinction ratio
          11.2.1.2 Distributed polarization crosstalk analyzer
     11.2.2 Basics of polarization crosstalk in PM fibers
          11.2.2.1 Classification of polarization crosstalk by causes
          11.2.2.2 Classification of polarization crosstalk by measurement results
     11.2.3 Characterization of potting adhesive with a DPXA
     11.2.4 Characterization of coil quality by polarization crosstalk analysis
     11.2.5 Polarization-maintaining fiber characterization and screening
          11.2.5.1 Measurement fixture
          11.2.5.2 Group birefringence and group-birefringence-uniformity measurements
          11.2.5.3 Group birefringence dispersion measurement
          11.2.5.4 Group birefringence thermal coefficient measurement
          11.2.5.5 PER measurement
          11.2.5.6 PM fiber-quality evaluation
     11.2.6 Single-mode fiber coil inspection
          11.2.6.1 Lumped PMD and PDL measurements
          11.2.6.2 Distributed transversal stress measurement
          11.2.6.3 Degree-of-polarization tests
11.3 Coil Transient Parameter Characterization
11.4 Tomographic (3D) Inspection of Fiber Gyro Coils
Acknowledgement
References

12 A Personal History of the Fiber Optic Gyro
Eric Udd
References

Appendix: Additional Fiber Rotation Sensor Books, Papers, and Patents
A.1 Fiber Optic Rotation Sensor Contents in Books and Paper Collections
References
A.2 Accessing the Fiber Optic Rotation Sensor Patent Literature
References

Preface

In the early years of aviation, guidance was provided by mechanical gyros based on spinning wheels or disks. According to the conservation of angular momentum, the orientation of the spinning object axis is unaffected by tilting or rotation of the support on which the spinning object is mounted. The spinning top therefore defines a direction in space that is used as a reference. By the end of the 1930s, the performance of mechanical gyros had improved considerably, and their use was widespread in commercial and military aircraft. World War II resulted in the mass production of mechanical gyros on an unprecedented scale, with increased accuracy and resolution. In subsequent years, the boom in commercial air travel and military requirements for improved aviation significantly expanded the marketplace for inertial navigation systems based on these gyroscopes.

The implementation of navigation systems for aerospace platforms remained an important issue as mechanical gyros were responsible for nearly 50% of aircraft departure delays. Thus, the demonstration of the ring laser gyro shortly after the invention of the laser became an area of extreme interest for both military and commercial aviation. The US Department of Defense spent hundreds of millions of dollars to support research and development, followed by funds to support the establishment of manufacturing lines at US companies in the 1960s and 1970s. These efforts led to the introduction of ring laser gyro systems onto military and commercial aerospace platforms in the late 1970 and early 1980s.

In the 1970s, the fabrication of the first low-loss single-mode optical fiber occurred at Corning. Shortly thereafter, Dr. Victor Vali and Professor Richard Shorthill at the University of Utah constructed and operated the first open-loop fiber optic gyro. Their idea was simple: construct a Sagnac interferometer with a multi-turn fiber coil, which increases the total area subtended by the coil in proportion to the number of turns and enhances the Sagnac phase shift by the same ratio. This opened up the possibility of moving away from the severe requirement associated with manufacturing ring laser gyros in ultra-clean environments with ultra-pure gases, very-low-expansioncoefficient ceramics, and very-low-backscatter mirrors.

An immediate issue with the fiber optic gyro involved the need for eight orders of magnitude of dynamic range for the navigation of aircraft and extreme linearity. The open-loop fiber optic gyro at the time seemed capable of a dynamic range of three or four orders of magnitude with sufficient levels of linearity. The solution introduced by Cahill and Udd at McDonnell Douglas Astronautics Company used a closed-loop fiber gyro approach that solved in principle the dynamic range and linearity issue with performance and underlying equations similar to those of the ring laser gyro. Like in other closed-loop systems, the output signal of the gyro, which is proportional to the rotation rate, is fed back to the phase modulator in the Sagnac loop in order to cancel the output signal. The readout of the gyro is then the feedback voltage applied to the modulator, which is also proportional to the rotation rate. The benefits of the closed-loop gyro stem from the fact that the output always equals or is very near zero, no matter how large the rotation rate is, up to a very large value imposed mostly by the large voltage dynamic range of the feedback circuit. The dynamic range is therefore greatly increased, and its linearity is excellent because the signal never deviates far from zero. This solution offered the potential for an all-solid-state rotation sensor with a lower overall cost.

Realizing the potential of the fiber optic gyro, like the ring laser gyro, has been a long and expensive process. Many researchers have made important enabling contributions, and many more engineers have worked diligently for many years on solving the problems associated with realizing viable inertial navigation and guidance at affordable costs. This book contains contributions from key engineers and scientists who have worked from as early as 1977 to the present on manufacturing high-performance fiber gyros for many applications.

In this book, Eric Udd provides a chapter that overviews early work on developing open-loop and closed-loop fiber gyros at McDonnell Douglas. These efforts resulted in the first solid-state fiber optic gyros and were highly directed toward demonstrating feasibility for a range of aerospace and oil and gas applications. In parallel, Professor John Shaw at Stanford University obtained funding from Litton Guidance and Control that fueled many successful years of research to improve the performance of fiber optic gyros. In particular, his research group pioneered a series of novel all-fiber components in its early years - especially fiber couplers with extremely low loss and backscattering, and a fiber polarizer with an exceedingly high extinction ratio - that were implemented to eliminate the bulk components used in McDonnell Douglas early prototypes and produced gyros with recordbreaking rotation sensitivities. Many of Professor Shaw's graduate students went on to make major contributions to fiber optic gyro technology, including Hervé Arditty and Hervé Lefèvre (at Thomson CSF, then Photonetics, and now IxBlue), George Pavlath (at Litton Guidance and Control, now Northrop Grumman), Ralph Bergh (who has founded and operated a series of companies supporting fiber gyros), and Michel Digonnet, who succeeded Professor Shaw at the Edward L. Ginzton Laboratory at Stanford.

Several people from the Stanford group have contributed chapters to this book. Hervé Lefèvre provides a "potpourri of fortunate events" that serves as a broad overview of the history and fundamental physics of the fiber optic gyroscope, and the events that turned out just right for fiber optic gyros. With Hervé Arditty, Hervé Lefèvre promoted the "minimum configuration" fiber optic gyro, i.e., the configuration that comprises the minimum number of components required to enforce reciprocity, a key property that was ultimately instrumental in the remarkable overall performance of the fiber optic gyroscope. These components were eventually implemented in an integrated-optic chip fabricated in lithium niobate, a technology that was also critical to the gyroscope's success. These insights, as well as the early development of effective phase modulation techniques, were among the key contributions they both made to fiber optic gyro technology. George Pavlath of Northrop Grumman overviews the state of the art of closed-loop fiber optic gyros and their applications. In the early 1980s, Litton Guidance and Control selected him to lead their fiber optic gyro program, and over the decades he has guided that group to many important achievements, including the implementation of fiber optic gyros on major aerospace platforms. Most notably, Litton Guidance and Control provided the compact closed-loop fiber gyros that navigated all of the Mars rovers, including Spirit, Opportunity, and Curiosity. Pavlath's chapter outlines the achievements of Litton Guidance and Control and Northrop Grumman. Ralph Bergh's chapter outlines a recently improved signal-processing approach for optimizing the closed-loop fiber gyro operation. The work at the Edward L. Ginzton Laboratory that Professor Shaw started continues under the direction of Professor Michel Digonnet. The chapter by Digonnet and his former graduate student Dr. Jacob Chamoun describes some of the latest efforts toward interrogating the fiber gyro with a coherent light source, instead of the conventional broadband light source, in order to produce the next generation of fiber gyros with improved scale-factor stability and reduced noise.

In the late 1970s, Professor Shaoul Ezekial at MIT demonstrated a different type of optical rotation sensor: the passive ring resonator. With James Davies, he later independently demonstrated a closed-loop fiber optic gyro similar to that of McDonnell Douglas. One of his students, Glen Sanders, joined Honeywell in Minneapolis in 1983. Honeywell was a leader in ring laser gyros but initiated research efforts in fiber optic gyros and resonant fiber optic gyros in the mid-1980s. This position increased in October 1986 when Honeywell acquired Sperry and their active fiber gyro program in Phoenix. Glen Sanders joined the Phoenix group in the late 1980s and became a leader of the fiber gyro program there. He was joined by key co-developer Lee Strandjord and, later, by Steve Sanders in 1998. They continued to develop fiber optic gyros, particularly for high-performance applications, and they have demonstrated state-of-the-art approaches in RFOGs. They, and other Honeywell co-authors, summarize the history and status of this work in their chapter.

Also in the early 1980s, Richard Dyott of Andrew Corporation led his group in developing D-shaped optical fiber with an elliptical core. The D shape enabled the fabrication of fiber polarizers and polarization-preserving optical fibers. Andrew Corporation made satellite dishes, and their focus was on stabilizing these units. KVH Industries, Inc. acquired the fiber gyro capabilities of Andrew Corporation and improved the linearity and range of the open-loop fiber gyro. The result has been successful at producing units for the middle range of the rotation sensor market. Jay Napoli of KVH outlines the state of the art of these developments in his chapter.

Other companies continue to enter the fiber gyro marketplace as key patents have expired and new methods for enhanced performance are developed. The chapter by Al Cielo Inertial Solutions, Ltd provides an example of this type of company.

One of the keys to success of the fiber optic gyro are components and associated packaging that meet stringent requirements to reduce error sources. Examples of these components include polarization-maintaining optical fiber with thin coatings suitable for winding, polarizing optical fiber packaged for maximum and stable extinction ratios, and fiber couplers. Overall, the properties of polarization-maintaining fibers, fiber polarizers, and fiber couplers have enabled reductions in the fiber gyro bias drift by many orders of magnitude. Chris Emslie describes the specialty optical fibers and components that have played a significant role in fiber gyro development, and offers examples produced by the University of Southampton, Fibercore, and other key players.

In a fiber optic gyro, the configuration and packaging of the fiber coil is particularly important to reduce the errors induced by temperature variations, acoustic waves, and strains, as required to achieve high performance. Steve Yao at General Photonics offers a close look at quadrupole fiber-coil windings and the associated test procedures that are used to meet this goal. The last chapter of the book is a personal history of the fiber gyro by Eric Udd. It provides a glimpse of some of the motivations, events, and people associated with the fiber gyro development and its introduction as an important product for many applications from 1977 to the present.

This book arose from efforts to form a special session to commemorate the 40th anniversary of the first hardware demonstration of the fiber gyro in 1976 by Vali and Shorthill. The invited expert papers published in the conference proceedings were extended and new material added in an effort to present both a historical perspective and a more in-depth representation of the existing state of the art. New chapters were prepared that extend the range of topics covered. We would like to thank the contributors to this book for their efforts over more than four decades to convert the dream of high-performance solid-state rotation sensors into reality.

Eric Udd
Michel Digonnet
June 2019


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