Fundamentals of Plastic Optical Fibers E-Book

Yasuhiro Koike

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 290

Veröffentlichungsjahr: 2014

Beschreibung

Polymer photonics is an interdisciplinary field which demands excellence both in optics (photonics) and materials science (polymer). However, theses disciplines have developed independently, and therefore the demand for a comprehensive work featuring the fundamentals of photonic polymers is greater than ever. This volume focuses on Polymer Optical Fiber and their applications. The first part of the book introduces typical optical fibers according to their classifications of material, propagating mode, and structure. Optical properties, the high bandwidth POF and transmission loss are discussed, followed by an outline on the propagating mode characteristics and how they affect the performances of the fiber. The second part of the book reviews conventional materials of POFs and gives an overview on fabrication methods. This is followed by a survey of characterization methods. Based on the characteristics of optical communication systems, the last chapter will concentrate on the many advantages of POF in link and network design. Written by a top expert in the field, this is an invaluable resource for semiconductor physicists, materials scientists, polymer chemists, electrical engineers, and those working in the semiconductor industry.

Leseprobe

Table of Contents

Cover

Related Titles

Title Page

Copyright

Preface

Acknowledgments

Chapter 1: Introduction: Faster, Further, More Information

1.1 Principle of Optical Fiber

1.2 Plastic Optical Fiber

References

Chapter 2: Transmission Loss

2.1 Absorption Loss

2.2 Scattering Loss

2.3 Low-Loss POFs

References

Chapter 3: Transmission Capacity

3.1 Bandwidth

3.2 Wave Propagation in POFs

3.3 Mode Coupling Effect in POFs

References

Chapter 4: Materials

4.1 Representative Base Polymers of POFs

4.2 Partially Halogenated Polymers

4.3 Perfluoropolymers

References

Chapter 5: Fabrication Techniques

5.1 Production Processes of POFs

5.2 Fabrication Techniques of Graded-Index Preforms

5.3 Extrusion of GI POFs

References

Chapter 6: Characterization

6.1 Refractive Index Profile

6.2 Launching Condition

6.3 Attenuation

6.4 Bandwidth

6.5 Near-Field Pattern

References

Chapter 7: Optical Link Design

7.1 Link Power Budget

7.2 Eye Diagram

7.3 Bit Error Rate and Link Power Penalty

7.4 Coupling Loss

7.5 Design for Gigabit Ethernet

References

Appendix Progress in Low-Loss and High-Bandwidth Plastic Optical Fibers

A.1 Introduction

A.2 Basic Concept and Classification of Optical Fibers

A.3 The Advent of Plastic Optical Fibers and Analysis of Attenuation

A.4 Graded-Index Technologies for Faster Transmission

A.5 Recent Studies of Low-Loss and Low-Dispersion Polymer Materials

A.6 Conclusion

Acknowledgment

References

Index

EULA

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Guide

Cover

Table of Contents

Preface

Chapter 1: Introduction: Faster, Further, More Information

List of Illustrations

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

Figure 2.7

Figure 2.8

Figure 2.9

Figure 2.10

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 3.7

Figure 3.8

Figure 3.9

Figure 3.10

Figure 3.11

Figure 3.12

Figure 3.13

Figure 3.14

Figure 3.15

Figure 3.16

Figure 3.17

Figure 3.18

Figure 3.19

Figure 3.20

Figure 3.21

Figure 4.1

Figure 4.2

Scheme 4.1

Figure 4.3

Figure 4.4

Figure 4.5

Figure 4.6

Figure 4.7

Scheme 4.2

Figure 4.8

Figure 4.9

Scheme 4.3

Scheme 4.4

Figure 4.10

Figure 4.11

Figure 4.12

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.7

Figure 5.8

Figure 5.9

Figure 5.10

Figure 5.11

Figure 5.12

Figure 5.13

Figure 5.14

Figure 5.15

Figure 5.16

Figure 5.17

Figure 5.18

Figure 6.1

Figure 6.2

Figure 6.3

Figure 6.4

Figure 6.5

Figure 6.6

Figure 6.7

Figure 6.8

Figure 6.9

Figure 6.10

Figure 6.11

Figure 6.12

Figure 6.13

Figure 6.14

Figure 7.1

Figure 7.2

Figure 7.3

Figure 7.4

Figure 7.5

Figure 7.6

Figure 7.7

Figure 7.8

Figure 7.9

Figure 7.10

Figure 7.11

Figure 7.12

Figure 7.13

Figure 7.14

Figure 7.15

Figure A.1

Figure A.2

Figure A.3

Figure A.4

Figure A.5

Figure A.6

Figure A.7

Figure A.8

Figure A.9

Figure A.10

Figure A.11

Figure A.12

Figure A.13

Figure A.14

Figure A.15

Figure A.16

Figure A.17

Figure A.18

Figure A.19

List of Tables

Table 2.1

Table 2.2

Table 2.3

Table 4.1

Table 4.2

Table 5.1

Table A.1

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Yasuhiro Koike

Fundamentals of Plastic Optical Fibers

The Author

Yasuhiro Koike

Professor, Keio University

Director, Keio Photonics Research Institute

Yokohama, Japan

Cover

The picture represents how light propagates through graded index POFs. The incident light draws a sine curve because GI POFs have parabolic refractive index profiles in the core regions.

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Preface

People in the industry formerly held the vague notion that polymers were unsuitable for application in the high-performance photonics field. Twenty odd years later, however, we have seen the birth of photonic polymers in applications such as the world's fastest plastic optical fiber (POF) and high-resolution displays. Research papers written in the first half of the twentieth century by Einstein and Debye, which delve into the essence of light scattering, have become my personal bibles. From them, I learned that the more we strive to achieve a breakthrough, the more important it is that we return to the fundamentals.

What originally drew me into the academic field of photonic polymers, a field which combines photonics and physical sciences, was my meeting with the late Professor Yasuji Otsuka, a person who I have the greatest respect for. I was a fourth year undergraduate student when I joined Professor Otsuka's laboratory in 1976. At that time, the laboratory had just begun its research into optically converging plastic rod lenses. By creating a graded index (GI) in the radial direction in a rod-shaped polymer, the light passing through it would travel in a meandering path, forming an image even when both ends of the rod were flat. I found this to be a most curious phenomenon and became fascinated by polymers. What interested me at first was why a GI causes light to bend gradually according to the refractive index profile. Professor Otsuka was an expert in polymer chemistry, focusing on emulsion polymerization, but he worked out and explained Maxwell's ray equation to me. I was very impressed and also surprised at the fact that he had gone beyond his particular field of polymer chemistry and was attempting to use optics and mathematics to explain the behavior of light in a polymer. I greatly admired Professor Otsuka.

Years later, I would find myself researching the fundamental reasons for light scattering loss – the prime reason why fibers could not be made transparent. While I remained a member of the polymer chemistry laboratory, on my own I entered the worlds of physics and optics as I studied subjects such as light scattering theory and polarization. I would continue to learn in the academic field of photonic polymers for the next 20 years, but my fundamental research method was the one that I learned at that time from Professor Otsuka.

In 1982, I received Ph.D. from Keio University and I was at a crossroads in my research into the question of whether it was truly possible to create a GI-type POF that could transmit optical signals at speeds exceeding one gigabit. The prototype GI-POF suffered from low transparency, and had a transmission loss of more than 1000 dB/km, preventing the light from traveling farther than a few meters. In order to achieve transmission speeds exceeding one gigabit, it was necessary to create a GI by adding another material inside the fiber and creating a density distribution in the radial direction. However, at the same time, determining how to eliminate impurities in order to make the POF transparent was a major issue. Therefore, attempting to achieve high-speed optical communication by adding another material (an impurity?) that would create a GI was a large challenge.

At that time, in order to create a gradient index, two monomers M1 and M2 with different reactivities were copolymerized. A polymer containing large quantities of the highly polymerizable M1 monomer with its low refractive index was gradually deposited around the periphery to create the gradient index. The created GI preform appeared transparent, but it was possible to see the light beam traveling in a pretty meandering path which was visible as a result of scattering of the light. We needed to reduce this light scattering loss by a factor of at least several hundreds. I was completely unaware of the large and theoretically impenetrable barrier which lays in the way of continuously improving the copolymerzation method which uses the different reactivities of the monomers to create the gradient index, and I continued to work toward creating a transparent GI-POF.

The problem of light scattering consumed me, and I was not able to assign this as a research theme for student graduation or master's theses because I did not know whether the research would produce any results. I continued to struggle with the problem on my own. As I was reading a broad range of documents on the subject, I came across Einstein's fluctuation theory of light scattering from the early twentieth century. This was based on micro-Brownian motion in solution, and it proposes that light scattering loss is proportional to isothermal compressibility. When I actually entered the isothermal compressibility of the POF material PMMA (poly(methyl methacrylate)), I obtained a value of 10 dB/km – much lower than the aforementioned value of 1000 dB/km. This meant that transmission over a distance exceeding 1 km was possible. This was truly a revelation to me at that time. However, in that case, where did the difference of 990 dB/km come from? In order to identify the kind of heterogeneous structure which was producing this excessive scattering, I learned everything I could about light scattering using Debye's correlation function from the 1950s. I also tried again to work the theory out on my own. This was an extremely useful theory for quantitative analysis of the relationship between micro nonuniform polymer structures and light scattering. What was wonderful about Debye's scattering theory was that it was possible to define the correlation function without hypothesizing the shape or size of the heterogeneous structures in the polymer chain. This makes it possible to experimentally find the correlation distance that includes information about the heterogeneous structure shape and size from the angular dependence of the light scattering. This became a powerful tool for me in working to identify the cause of excess polymer scattering.

At the same time, I began to see how the method of forming a gradient index according to differences in reactivity would form an extreme polymer compositional distribution in the generated copolymer. It became clear that, as we tried to make the gradient index larger by increasing the difference in reactivity, the polymer composition would contain increasing amounts of components that were similar to homopolymers of M1 and M2. This essential large heterogeneous structure reached sizes in excess of several hundred angstroms, and when applied to Debye's light-scattering theory, I discovered it to be the cause of an enormously large scattering loss exceeding several hundred decibels per kilometer. This realization was the culmination of many long years of research and allowed me to recognize that the fiber would theoretically not become transparent utilizing processing methods that rely on monomer reactivity.

I began experiments based on the completely new idea of forming a gradient index using the sizes of the molecules instead of the monomer reactivity. I still remember the day very clearly. It was April 1, 1990 (April Fool's Day). On that day, I had produced a superbly transparent GI-POF preform. This was the moment I emerged from my 10-year-long search for a solution to scattering loss. Our laboratory was galvanized from this point on. Our course was clearly set, and all student research themes were channeled in this direction. Test data on GI-POF with increasingly lower losses and higher speeds were produced one after another. I obtained a patent, wrote numerous papers, and began joint research with industry all at once. News that an optical signal with speed exceeding a gigabit passed through 100 m of GI-POF for the first time was reported on August 31, 1994, on the front page of the Nikkei Shimbun (newspaper).

The production method up until around 2005 was the preform method (a manufacturing method where a GI preform is created, which is then made into GI-POF through heat-drawing) with a focus on the interfacial-gel polymerization method. However, from around 2005, we began to develop the continuous extrusion method in earnest, and by 2008 succeeded in 40-Gb transmission. This was the world's fastest transmission speed, surpassing the GI-type silica optical fiber. We achieved these results through joint research with Asahi Glass. It was based on the essential principle of the materials, which indicates that a perfluorinated polymer used as the POF core material has a lower material dispersion compared to silica. (Material dispersion determines the transmission bandwidth.)

My research into light scattering, which I have described here, has been supported by the research papers that were written by Einstein and Debye during the first half of the twentieth century, and which delve into the essence of light scattering. Through these papers, I realized that the latest research papers would not always be useful in pursuing leading-edge research. I learned that the more we strive to achieve a breakthrough, the more important it is that we return to the fundamentals.

Yasuhiro Koike

Acknowledgments

This book was written by Yasuhiro Koike with inputs from Kenji Makino (Chapters 1, 3, 6, and 7), Azusa Inoue (Chapters 2 and 3), and Kotaro Koike (Chapters 2, 4, and 5), Project Assistant Professors of Keio Photonics Research Institute, Keio University, Japan. Their works were supported by the Japan Society for the Promotion of Science (JSPS) through its “Funding Program for World-Leading Innovative R&D on Science and Technology” (FIRST Program).

1Introduction: Faster, Further, More Information

The realization of these three features has motivated the development of communication systems since the dawn of history. Optical communication systems in the broad sense date back to ancient times. One of the earliest optical communication systems was fire and smoke. Although atmospheric conditions, such as rain, snow, fog, and dust, strongly affect the transmission reliability, this type of optical communication was used for a long time worldwide. In addition to the sensitivity to the environmental conditions, the signal receiver was the human eye; thus, the transmission system had poor reliability. More stable and dependable communication systems were developed; for instance, a courier or pigeon carried messages and letters.