We describe a new type of optical reflectometry which is useful in testing single-mode lightguide systems. This technique uses a scanning Michelson interferometer in conjunction with a broadband illuminating source and cross-correlation detection. High resolution is achieved through the limited coherence of the backscattered radiation. With this approach it is possible to distinguish scattering centers separated by only a few micrometers. In some cases loss may be estimated for components in the transmission path of a test lightguide. The basic principles of this diagnostic technique, along with some performance characteristics, are illustrated for an all-fiber reflectometer. We also discuss several laboratory applications which serve to demonstrate the resolution capabilities of this measurement concept.

It is a challenging task to revise a book that has already enjoyed many years of success. It is an honor to be asked to undertake this latest revision of what has now been several editions. I have had a deep belief in these books ever since I first used them as a young theory teacher in 1967 when they were first available. With a great deal of history behind me, and the highest respect and regard for all of Paul Harder's diligent efforts, I now offer various revisions and enhancements that I believe keep to the original spirit of Dr. Harder's programmed concept, and that I hope all users will find helpful as they work through these pages. In making the revisions, I have responded to comments that were made available to me from Dr. Harder's estate and to suggestions from reviewers and current users of the book. Earlier revisions contained additions made to the supplementary exercises and to the Appendix material. In selected places throughout the book, I have continued to clarify definitions or to demonstrate to the reader that there are always alternatives to the ideas presented and that the reader should explore those alternatives either independently or in class with the instructor. This edition sees further changes in or additions to selected exercises, changes in the Appendixes, and the addition of "Supplementary Activities." I hope that the differences in theoretical and analytical approaches (which, I know, will always be there) work comfortably with this book and also provide many interesting points of discussion in class. I'm quite sure that Dr. Harder never intended this volume to be the final, definitive answer but, rather, to provide an informed point of departure for exploring the many anomalies that are always to be found in musics everywhere. 7/19/06 9:33 AM both a performer and a listener. The purpose of conceptualizing musical processes is to render more understandable the responses elicited by the auditory stimuli of music. Remember, music is an aural art; it is apprehended better by the ear than by the eye. An icon beside a frame indicates that the music in that frame is reproduced on the compact disc.

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