Table Of ContentEPO APPLIED TECHNOLOGY SERIES
OTHER TITLES IN THE SERIES
Volume 1 CARDON & FRANSEN Dynamic Semiconductor RAM Structures
Volume 2 LAMMINEUR & CORNILLIE Industrial Robots
Volume 3 BRACKE et al. Inorganic Fibres & Composite Materials
Volume 4 HOORNAERT Reverse Osmosis
Volume 6 JACOBS et al. Nickel & Cobalt Extraction Using
Organic Compounds
Volume 7 CRISTOL Solid State Video Cameras
Volume 8 CORNILLIE & DA VIES Microprocessors
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Optical Fibres
J. GEISLER
G. BEAVEN
J. P. BOUTRUCHE
European Patent Office, The Hague, The Netherlands
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Copyright © 1986 European Patent Office
All Rights Reserved. No part of this publication may be reproduced,
stored in a retrieval system or transmitted in any form or by any means:
electronic, electrostatic, magnetic tape, mechanical, photocopying,
recording or othenvise, without permission in writing from the
copyright holders.
First edition 1986
Library of Congress Cataloging in Publication Data
Geisler, J. A.
Optical fibres.
(EPO applied technology series ; v. 5)
Includes index.
1. Optical communications. 2. Optical fibers.
I. Beaven, G. L. II. Boutruche, J. P. III. Title
IV. Series.
TK5103.59.G44 1986 621.38Ό414 86-787
British Library Cataloguing in Publication Data
Geisler, J A.
Optical fibres.—(EPO applied technology series; v. 5)
1. Fibre optics
I. Title II. Beaven, G. L. III. Boutruche, J. P.
IV. Series
621.36'92 TA1800
ISBN 0-08-030577-6
In order to make this volume available as economically and as rapidly
as possible the authors' typescripts have been reproduced in their
original forms. This method unfortunately has its typographical
limitations but it is hoped that they in no way distract the reader.
Printed in Great Britain by A. Wheaton & Co. Ltd., Exeter
Foreword
A long way has been gone since Graham Bell's proposal to send speech over
visible light beams, a century ago. Since then, low-loss fibres, high-
power LED's and lasers as well as sensitive p-i-n and APD detectors have
provided the basis for a new technology, allowing the transition from a
laboratory curiosity into operational use. Nhy is there such an interest
in this new communication medium? Let a single example provide the answer.
A copper link between a radar transceiver and its consoles requires 47
cables carrying 375 separate signal lines and five hefty copper wires to
help subdue the effects of large earth loops. The copper installation
weighs 7 tons and costs $ 1 million. The fibre-cable version requires a
single cable of seven strands, weighs 15 pounds and costs $ 30,000.
This is not enough. A fibre-optic link has many advantages, a few dis
advantages and many potential applications.
Advantages
smaller cable size and weight (easier to install, to handle, to store)
compatible with integrated-circuit dimensions
immunity to electromagnetic interference (radiofrequency or electro
magnetic-pulse interference)
eliminates earth loops
no electromagnetic emission (does not radiate any signals and has no
noise emission problems), few cross-talk problems, security against
electromagnetic eavesdropping
much greater bandwidth (accepts wide-band or multiplexed signals),
easily upgraded in bandwidth
v
vi FOREWORD
free from sparking, safe in explosive atmosphere, no short-circuits,
does not attract lightning, freedom to route cable through water, at a
high temperature, in a highly electrical field
handles high voltages without isolation transformers
potentially lower cost, savings in energy.
Disadvantages
as a new phenomenon, may need trained personnel familiar with inter
connection techniques and suffer customer acceptance problems due to a
reluctance to abandon well-proven systems
not yet standardized, possibly existing inferior-product support
inherent limitations such as light-launching difficulties, attenuation
in sharp bends, reflection noise, backward scattering, etc.
Applications
Earth-based systems
The "wired city" concept. It is expected that copper cables can be
exchanged for fibre-optic cables in a 1 : 1 proportion in existing
conventional services (telephony, cable TV, data transmission), ISDN
(integrated services digital networks) are in the making.
Long-haul transmissions with repeaters at a national or international
network level (digital and analogous).
Medium- and short-haul applications such as private signal wiring or
printed-circuit board to printed-circuit board signal transfer,
cabling in severe environments (nuclear, chemical), computer networks,
distributed-data processing.
Measuring instrumentation.
° Industriai control with optical sensors, signal transfer from rotating
parts.
Submarine cabling.
° Applications in power plants, radar installations, railroad
operations, petroleum explorations, motor cars, medicines, robotics.
Avionics cabling with substantial weight reduction.
° Navionics cabling (aboard-ship systems).
FOREWORD vii
Potential Market
The world-wide market share of fibre-optics is estimated at $ 600
million in 1985 and at $ 1,000 million in 1990.
Fibre-optic transmission challenges the satellite links, radio links and
all kinds of wire links. In addition to being a replacement of existing
services, fibre-optic links compete for applications such as broad-band
integrated networks offering new services (alarm, banking, etc.).
Predictions related to fibre-optics production.
In 1985 : 1 million km at $ 0.6 a meter : $ 600 million.
In 1990 : 10 million km at $ 0.1 a meter : $ 1,000 million.
Present Situation
Fibre-production capacity 800,000 km/year, 40 manufacturers of data links,
multiplexers and transducers, 15 experimental fibre-optic local networks.
Future of the Fibre-Optic Technology
This new technology will compete with existing transmission technology and
probably supersede a great deal of it. In the mean time, many new
components such as integrated optics will have to prove that the photon
can replace the electron. Right now, it looks that way. Undoubtedly, the
new technology will have a great impact on diverse systems, with social
and cultural implications.
The Monograph
Such an interest in fibre-optic technology goes along with much research
and patent activity. However, we feel that this technology remains a
mystery to many engineers and scientists. The aim of the present monograph
is to clear up the mystery by explaining the technology from a practical
point of view by making use of the latest information disclosed in patent
and other literature from all over the world. In particular, this
monograph is a survey of such literature to be found in the parts of the
systematically arranged search files of the European Patent Office
referred to as subclasses C03B, G02S and H04B of the International Patent
Classification.
viii FOREWORD
The monograph is divided into three parts : the first one deals with the
manufacture of optical fibres, the second describes optical-fibre
connectors, terminals and branches, and the third one is concerned with
the major optoelectronic components encountered in optical-communication
systems.
Since there are thousands of relevant documents, this survey cannot refer
to all of them and a selection had to be made. Ne have eschewed the
historical approach and, instead, have chosen those documents which best
illustrate the present state of the art in all its variations. Thus, along
with selecting documents representing the main aspects, we have also
selected those which show, and claim to solve, the various practical
difficulties that can arise.
The documents chosen have been abstracted and/or important sections have
been quoted. If a particular patent or article is of interest, greater
detail and further embodiments can usually be obtained from the full
version. Similar or related patents have also been mentioned so as to
provide the reader with a basis for further investigation. Furthermore,
since many modern patents (US, GB, DE, EP, NO) nowadays publish the
citations that have been raised against them, one can quickly build up a
detailed picture by looking up these citations.
For convenience, the patent and other documents have been referred to by
their number or title.*
It has been assumed that the reader has no previous knowledge of the
subject and so, whenever possible, the simplest examples of each aspect
have been used. However, no necessary complexity has been deliberately
avoided and the survey should mention all the details and techniques
required for a comprehensive knowledge of the art presented here.
A monograph of this sort, reflecting current thinking in topical areas of
technology, will be useful to research scientists and engineers or patent
personnel who are engaged in the field concerned.
It also provides the newcomer with an opportunity to familiarize himself
with the specific problems of the technology involved.
Taking into account that patent literature is, in many areas, from five to
six years ahead of the final development of its subject, such a monograph
provides a working tool much more up to date than traditional books or
manuals usually written and published after the final development stage.
* See "Note on Cited Patent Documents" (opposite page).
NOTE ON CITED PATENT DOCUMENTS
In this monograph, a great number of patents and published patent
applications are cited, using an international two-letter country code,
i.e. :
DE = Germany (Federal Republic)
EP = European Patent Office (EPO)
FR = France
GB = United Kingdom
JP = Japan *)
NL = The Netherlands
SU = USSR
US = United States of America
NO = International Bureau of N.I.P.O. **)
*) All cited documents are published patent applications (Kokai Tokkyo).
**) Patent applications published under the Patent Cooperation
Treaty (PCT).
OF-A* i x
CHAPTER I
Manufacture of Optical Fibres
SUMMARY : PAGE
INTRODUCTION 4
SECTION A : PRODUCTION OF PREFORMS 6
1. STARTING FROM MOLTEN GLASS 6
2. BY REFORMING PREFORMED GLASS BODIES INTO A PREFORM 12
3. BY CHEMICAL MEANS 22
3.1. Inside Vapour Deposition 22
3.1.1. Substrate pretreatments 22
3.1.2. Control of the quantity of the reactants and their 22
introduction into the substrate tube
3.1.3. Seals 27
3.1.4. Heating burners 28
3.1.5. Control and regulation systems 31
3.1.6. Reaction products exhaust 35
3.1.7. Collapsing into a rod 36
3.1.8. Miscellaneous 39
3.2. Plasma Chemical-Vapour Deposition 40
3
4 OPTICAL FIBRES
3.3. Vapour Axial Deposition (VAD) 50
3.3.1. General description of the process 50
3.3.2. Torches 54
3.3.3. Control of the process 59
3.3.4. Post-treatment of the preform 61
3.3.5. Miscellaneous 62
3.4. Outside Vapour Deposition 66
3.4.1. General description of the process 66
3.4.2. Mandrels 68
3.4.3. Heating systems 71
3.4.4. Control systems 72
3.4.5. Consolidating 74
3.4.6. Introduction of dopant after preform-making 78
3.5. Processes using Liquid Reactants 79
SECTION B : DRANING OF OPTICAL FIBRES 90
1. STARTING FROM THE MOLTEN GLASS; DOUBLE-CRUCIBLE TECHNIQUE 90
2. STARTING FROM A PREFORM 99
3. COMBINED SYSTEMS 114
SECTION C : POST-TREATMENT OF OPTICAL FIBRES 120
1. ORGANIC COATINGS 120
2. INORGANIC COATINGS 132
INTRODUCTION
As mentioned in the foreword, there are many advantages to the use of optical
fibres versus the use of copper wires. Among these, a better prospect for the
raw materials : the earth's reserves of copper are decreasing continuously
while the silica reserves, representing 14 1 of the mass of the earth crust,
are almost inexhaustible. An optical fibre usually consists of a core, a
cladding and a coating. Core and cladding are almost always made of glass
while the coating, the purpose of which is to protect the interior of the
fibre, is made of plastic material.
The cladding possesses a smaller refractive index than the core does. Thus,
due to the reflexion of light on the cladding surface, it will force the light
to travel along the fibre axis.
