PREFACE

The first fiber optic sensors were the flexible endoscopes developed in the first half of the twentieth century. Their development and use created a revolution in medicine that continues to this day. The modern age of fiber optic sensors was enabled by the development of extremely low‐loss optical fibers in the mid‐1970s. A wide variety of sensor types and applications have been demonstrated for almost 50 years since reports of the early fiber optic sensors appeared in the literature.

There have been three distinct waves of fiber optic sensor development that can be identified with the types of fiber optic sensors associated with them. The most successful sensors of the first wave were the fiber optic gyroscopes based on the Sagnac effect and fiber optic hydrophones based on Mach–Zehnder and Michelson interferometers. These sensors were developed to the point of practicality with both commercial and military systems in use today. The second wave of fiber optic sensors was based upon Fabry–Perot interferometers, either extrinsic or intrinsic. A wide variety of applications using these sensors have been reported in the literature. The third wave of fiber optic sensors began with the development of in‐line Bragg grating optical filters for optical communication purposes. It was soon found that fiber Bragg gratings, or FBGs, made excellent optical transducers for sensing several different parameters. The fourth and most recent dramatic wave has been the realization of distributed fiber optic sensors for acoustics, pressure, temperature, and strain. Within each wave of development, many new transducer concepts have been demonstrated and reported to support an ever‐increasing array of applications.

The third edition of this book retains most of the second edition chapters associated with fundamentals, key concepts, and technology of fiber optic sensor technology. Eight new chapters have been written to support the third edition, and two more have been updated. Some chapters have been dropped to enable the third edition to be contained in a single volume.

This third edition of the book is comprised of 22 chapters. The first chapter serves as a guide to the content of the book as well as providing an overview of the history and direction of fiber optic sensor technology. Chapters 2 through 5 introduce the fundamentals of the components associated with fiber sensors. Chapter 2 on optical fibers for sensors has been rewritten and greatly expanded by Emslie to cover the many new implementations of optical fiber in a wide span of applications. Chapter 6 provides a brief overview of a selection of intensity‐based fiber sensors and those based on Fabry–Perot etalons. Polarization‐based fiber sensors are introduced in Chapter 7 with examples of multimode implementations. The important class of interferometric fiber sensors based on the Sagnac, Mach–Zehnder and Michelson interferometers are covered in Chapters 8 through 12. The Sagnac interferometer Chapters 8 and 9 cover fiber optic gyros and derivative classes of acoustic, distributed, and strain sensors as well as secure fiber communication. Chapters 10 and 11 on the Mach–Zehnder and Michelson interferometer focus on important acoustic applications and link strongly to Chapter 12 on multiplexing. Chapters 9 and 11 provide updates on the status of these classes of fiber sensors that have a long history of development, resulting in their being among the most commercially successful class of fiber sensors. Chapters 13 and 14 are new, extensive chapters on distributed sensing techniques that are rapidly emerging as an extremely important class of fiber optic sensor technology that also has direct impact on fiber optic communication systems. Chapter 15 provides a brief overview of fiber optic smart structures that serves as an introduction in part to the next five chapters of the book. Chapters 16 and 17 are extensive chapters on fiber optic grating sensors. Chapter 16 introduces a series of fiber grating sensors and multiparameter sensing with a wide variety of application examples often related to fiber optic smart structures. Chapter 17 is highly directed toward extensions of fiber optic grating sensor technology to withstand extreme environments. The next five chapters of the book are devoted to the fields of application of fiber optic sensor technology in more depth than in the prior chapters. Chapter 18 explores fiber sensors in civil structures. Chapter 19 reviews the application of fiber optic sensors in the oil and gas industry. Chapter 20 overviews the emerging field of fiber optic biosensors in some detail. Chapter 21 reviews fiber optic magnetic sensors. Chapter 22 provides an introduction to fiber sensors used to support industrial processes.

The editors of this book have been involved in the development of fiber optic sensors from the very beginning. In the early 1980s, the United States Naval Research Laboratory issued two contracts to demonstrate fiber optic hydrophone systems. Eric Udd worked on the single‐mode fiber optic hydrophone program at McDonnell Douglas, while Bill Spillman worked on the parallel multimode fiber optic hydrophone program at the Sperry Research Center. It was at that time that the editors became acquainted and discovered that they both were in the early stages of writing books on fiber optic sensors. Since Eric was further along in writing his book, it was decided that Bill would contribute a few chapters to Eric’s book and abandon his own effort. These chapters were included in the first edition of this book. Both Eric and Bill remained active in the development of fiber optic sensors throughout their careers, up until the present.

In this third edition of Fiber Optic Sensors: An Introduction for Engineers and Scientists, we provide engineers, scientists, graduate students, and advanced undergraduates with an introduction to the field of fiber optic sensors. To do this, the book contains all the necessary scientific and technical background material to allow a technical understanding of the sensors described. As can be seen from the table of contents, a great many different sensor types have been developed over the years. It has been more than a decade since the second edition of the book was published. Since that time, fiber optic sensing has become a mature part of the sensing marketplace with many successful sensor and sensor system products in areas ranging from aerospace, to civil structures, oil and gas, the medical field and electrical power. In this book, we showcase the most successful of these and their applications. We bring the book up to date by describing in detail the exciting new fiber optic sensor technologies that will take the field into the future.

It is interesting to note that many of the original concepts described in the first and second editions of this book turned out to be impractical at the time due to the lack of cost‐effective technologies to implement them. Many of the patents on these concepts have now expired, so they are free to be used by the technical community at large. More importantly, however, the base of fiber optics and other component technologies progressed to the point that several of the original concepts that were abandoned then are now practical and can be applied to solve today’s sensing problems.

No undertaking as comprehensive as that represented by this book could ever be successful without the support of more friends and colleagues than could possibly be named. Bill Spillman would particularly like to thank all past and present contributors to the “Fiber Optic Sensors” series of conferences that began in 1982 in London and have continued to this day. Without the talented and exceptional people who have made those conferences a success, there would be no field of fiber optic sensing today. Bill would also like to especially cite the contributions of Sir D. E. N. Davies, one of the pioneers of the field, and the legions of now very successful students that he trained in his laboratory at University College London. He would also like to offer his thanks to the colleagues at the Sperry Research Center with whom he worked on some of the first multimode fiber optic sensors: Don McMahon, Richard Soref, Art Nelson, Bob Gravel, and Larry Sheppard, a great team to be a part of. Eric Udd would like to thank his coworkers at McDonnell Douglas who supported much of his early work on fiber optic sensors including Richard Cahill who acted as his mentor during his early work on fiber optic gyros and fiber optic acoustic sensors, Bruce Turner and Paul Theriault who provided excellent technical support for many years, and his many colleagues and friends at McDonnell Douglas including Steve Watanabe, Stuart Higley, Al Joseph, Wil Otaguro, Jeff Eck, Russ Johnson, Robert Rice, and Tom Weaver who worked for and/or with him over the 16 years he worked at McDonnell Douglas. Eric would also like to thank the many people who worked with and for him at Blue Road Research including John Seim, Mike Morrell, Whitten Schulz, John Corones, Stephen Kreger, Marley and Wesley Kunzler, Bob McMahon, Caryn Major, and Sean Calvert. He would like to thank the many people who have sponsored and championed his work on fiber optic sensors over the years especially Wolfgang Schubel of Wright‐Patterson AFB and Captain John Ryan of Eglin AFB for sponsoring his efforts on fiber optic gyros; Jim Dorr and Kelli Corona‐Bittick of Production Products who sponsored and teamed on early work on fiber...