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【12月8日大公报讯】诺贝尔奖得主高锟的获奖演说
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诺贝尔奖得主高锟的获奖演说
【大公报讯】综合外电斯德哥尔摩2009年12月8日消息：身在瑞典的今届诺
贝尔物理学奖得主高锟，昨日下午由夫人黄美芸在斯德哥尔摩大学代为发表演讲。
历时两小时的演讲会，回顾了光纤理论的基础和对世界的影响，展示了高锟一流
科学家对科研的创见、自信与坚持。
演辞开首黄美芸先自我介绍，并对丈夫未能亲自演讲表示歉意。黄美芸在演
说中回忆高锟在众人质疑声音中坚持自己的信念，最后使光纤通信得到世人认可
的点点滴滴。
醉心研究归家迟
黄美芸回忆起四十多年前，高锟总是因为醉心于光纤研究而很晚回家，以至
年幼的子女要在餐桌前等爸爸回来才能开饭。黄美芸每次都很生气，依稀还记得
高锟总是说：“别生气，我们现在做的是非常振奋人心的事情，有一天它会震惊
世界的。”黄美芸当时略带讽刺地说：“是吗？那你会因此获得诺贝尔奖吗？”
幽默而心酸的回忆，引发台下笑声，一直坐在台下凝神聆听夫人演讲的高锟
亦被逗得咧嘴而笑。黄美芸表示，回望过往才发现，高锟是对的，“他的成果给
通信界带来了一场惊天动地的革命。”
黄美芸娓娓道出一九六○年代高锟研发光纤的时代背景及理论简介，谈及当
年物理学界已有光通讯的理论，不过无法制造出可长距离传输光信息的物料。当
时高锟认定传送物料才是关键，便埋首研究制作光纤的方法，终在一九六六年发
表光通讯理论，指人类可制作出极高纯度的玻璃纤维，取代传统铜线传送极高容
量资料。演辞讲述一九七○年代科学界如何利用高锟的理论，并由康宁玻璃工厂
以石英制造出世界第一条光纤，自此“光纤”技术一日千里，带来世界通讯革命。
历年诺贝尔奖得奖者皆在领奖前夕，在瑞典首都发表得奖演讲，综述生平最
重要的研究成就和学术思想。由于患阿兹海默症（老人痴呆症一种）的高锟发言
有困难，今次演讲由太太黄美芸代为以英语发表。
据了解，高锟夫妇于十月获通知得奖后，即联络中大寻求协助，其中与高锟
相识多年的中大副校长兼物理学家杨纲凯，和另外两名在一九九○年代由高锟邀
请到中大的工程学“传人”，现任中大讯息工程学系教授张国伟和陈亮光，即义
不容辞组成专家小组，协助完成这篇学术性甚浓的演讲。
亘古砂石递捷音
演辞由黄美芸亲自点题为“亘古砂石递捷音”（Sand from centuries past:
Send future voices fast），以英文写成。（编者按：光纤必须用高度纯净的
二氧化硅来做，否则光（以及它所负载的声音）就会受散射而不能够在里面传播
很远，而最普通的砂子正是二氧化硅。）
瑞典皇家科学院常任秘书贡诺．厄奎斯特在记者招待会上说，高锟在“有关
光在纤维中的传输以用于光学通信方面”取得了突破性成就，他将获得今年物理
学奖一半的奖金，共五百万瑞典克朗（约合七十万美元）；博伊尔和史密斯发明
了半导体成像器件──电荷耦合器件（CCD）图像感测器，将分享今年物理学奖
另一半奖金。
下面是英文演讲内容（来自信报网）：
Sand from centuries past;Send future voices fast.
A Nobel Lecture organized by the Royal Swedish Academy of Sciences
and The Prize Committee in Physics delivered by Mrs Gwen MW Kao
on behalf of Prof Charles K Kao Nobel Laureate in Physics 2009
8 December 2009 Aula Magna Stockholm University
1. Introduction
It is sad that my husband, Professor Charles Kao, is unable to give
this lecture to you himself. As the person closest to him, I stand
before you to honour him and to speak for him. He is very very proud
of his achievements for which the Nobel Foundation honours him. As are
we all!
In the 43 years since his seminal paper of 1966 that gave birth to the
ubiquitous glass fiber cables of today, the world of telephony has
changed vastly. It is due to Professor Kao’s persistence in the face
of skepticism that this revolution has occurred.
In the 1970s the pre-production stage moved to ITT Corp Roanoke VA, USA.
Whilst Charles worked there, he received two letters. One contained a
threatening message accusing him of releasing an evil genie from its
bottle; the other, from a farmer in China, asked for a means to allow
him to pass a message to his distant wife to bring his lunch. Both
letter writers saw a future that has since become past history.
In the 1960s, our children were small. Charles often came home later
than normal – dinner was waiting as were the children. I got very
annoyed when this happened day after day. His words,maybe not exactly
remembered, were –‘Please don’t be so mad. It is very exciting what
we are doing; it will shake the world one day!’ I was sarcastic,
‘Really, so you will get the Nobel Prize, won’t you!’
He was right – it has revolutionized telecommunications.
2. The early days
In 1960, Charles joined Standard Telecommunications Laboratories Ltd.
(STL), a subsidiary of ITT Corp in the UK, after having worked as a
graduate engineer at Standard Telephones and Cables in Woolwich for
some time. Much of the work at STL was devoted to improving the
capabilities of the existing communication infrastructure with a focus
on the use of millimeter wave transmission systems.
Millimeter waves at 35 to 70 GHz could have a much higher transmission
capacity. But the waters were uncharted and the challenges enormous,
since radio waves at such frequencies could not be beamed over long
distances due to beam divergence and atmospheric absorption. The waves
had to be guided by a waveguide. And in the 1950’s, R&D work on low
loss circular waveguides –HE-11 mode – was started. A trial system
was deployed in the 1960s. Huge sums were invested, and more were
planned, to move this system into the pre-production stage. Public
expectation for new telecommunication services such as the video phone
had heightened.
Charles joined the long-haul waveguide group led by Dr Karbowiak at STL.
He was excited to see an actual circular waveguide. He was assigned to
look for new transmission methods for microwave and optical
transmission. He used both ray optics and wave theory to gain a better
understanding of waveguide problems – then a novel idea. Later, his
boss encouraged him to pursue a doctorate while working at STL. So
Charles registered at University College London and completed the
dissertation ‘Quasi-Optical Waveguides’ in two years.
The invention of the laser in 1959 gave the telecom community a great
dose of optimism that optical communication could be just around the
corner. The coherent light was to be the new information carrier with
capacity a hundred thousand times higher than point-to-point
microwaves –based on the simple comparison of frequencies: 300
terahertz for light versus 3 gigahertz for microwaves.
The race between circular microwave waveguides and optical
communication was on, with the odds heavily in favour of the former.
In 1960, optical lasers were in their infancy, demonstrated at only a
few research laboratories, and performing much below the needed specs.
Optical systems seemed a non-starter.
But Charles still thought the laser had potential. He said to himself:
‘How can we dismiss the laser so readily? Optical communication is
too good to be left on the theoretical shelf.’
He asked himself the obvious questions:
1. Is the ruby laser a suitable source for optical communication?
2. What material has sufficiently high transparency at such wavelengths?
At that time only two groups in the world were starting to look at the
transmission aspect of optical communication, while several other
groups were working on solid state and semiconductor lasers. Lasers
emit coherent radiation at optical frequencies, but using such
radiation for communication appeared to be very difficult, if not
impossible. For optical communication to fulfill its promises, many
serious problems remained to be solved.
3. The key discovery
In 1963 Charles was already involved in free space propagation
experiments: the rapid progress of semiconductor and laser technology
had opened up a broader scope to explore optical communication
realistically. With a helium-neon laser beam directed to a spot some
distance away, the STL team quickly discovered that distant laser
light flickered. The beam danced around several beam diameters because
of atmospheric fluctuations.
The team also tried to repeat experiments done by other research
laboratories around the world. For example, they set up con-focal lens
experiments similar to those at Bell Labs: a series of convex lenses
were lined up at intervals equal to the focal length. But even at the
dead of night when the air was still and even with refocusing every
100 meters, the beam refused to stay within the lens aperture.
Bell Labs experiments using gas lenses were abandoned due to the
difficulty of providing satisfactory insulation while maintaining the
profiles of the gas lenses. These experiments were struggles in
desperation, to control light travelling over long distances.
At STL the thinking shifted towards dielectric waveguides. Dielectric
means a non-conductor of electricity; a dielectric waveguide is a
waveguide consisting of a dielectric cylinder surrounded by air. Dr
Karbowiak suggested Charles and three others to work on his idea of a
thin film waveguide.
But thin film waveguides failed: the confinement was not strong enough
and light would escape as it negotiates a bend.
When Dr Karbowiak decided to emigrate to Australia, Charles took over
as the project leader and he then recommended that the team should
investigate the loss mechanism of dielectric materials for optical
fibers.
A small group worked on methods for measuring material loss of
low-loss transparent materials. George Hockham joined him to work on
the characteristics of dielectric waveguides.
With his interest in waveguide theory, he focused on the tolerance
requirements for an optical fiber waveguide; in particular, the
dimensional tolerance and joint losses. They proceeded to
systematically study the physical and waveguide requirements on glass
fibers.
In addition, Charles was also pushing his colleagues in the laser
group to work towards a semiconductor laser in the near infrared, with
emission characteristics matching the diameter of a single-mode fiber.
Single mode fiber is optical fiber that is designed for the
transmission of a single ray or mode of light as a carrier. The laser
had to be made durable, and to work at room temperatures without
liquid nitrogen cooling. So there were many obstacles. But in the
early 1960s,
esoteric research was tolerated so long as it was not too costly.
Over the next two years, the team worked towards the goals. They were
all novices in the physics and chemistry of materials and in tackling
new electromagnetic wave problems. But they made very credible
progress in considered steps. They searched the literature, talked to
experts, and collected material samples from various glass and polymer
companies. They also worked on the theories, and developed measurement
techniques to carry out a host of experiments. They developed an
instrument to measure the spectral loss of very low-loss material, as
well as one for scaled simulation experiments to measure fiber loss
due to mechanical imperfections.
Charles zeroed in on glass as a possible transparent material. Glass
is made from silica –sand from centuries past that is plentiful and
cheap.
The optical loss of transparent material is due to three mechanisms: (a)
intrinsic absorption, (b)extrinsic absorption, and (c) Rayleigh
scattering. The intrinsic loss is caused by the infrared absorption of
the material structure itself, which determines the wavelength of the
transparency
regions. The extrinsic loss is due to impurity ions left in the
material and the Rayleigh loss is due to the scattering of photons by
the structural non-uniformity of the material. For most practical
applications such as windows, the transparency of glass was entirely
adequate, and no one had studied absorption down to such levels. After
talking with many people, Charles eventually formed the following
conclusions.
1. Impurities, particularly transition elements such as iron, copper,
and manganese, have to be reduced to parts per million or even parts
per billion. However, can impurity concentrations be reduced to such
low levels?
2. High temperature glasses are frozen rapidly and therefore are more
homogeneous, leading to a lower scattering loss.
The ongoing microwave simulation experiments were also completed. The
characteristics of the dielectric waveguide were fully defined in
terms of its modes, its dimensional tolerance both for end-to-end
mismatch and for its diameter fluctuation along the fiber lengths.
Both the theory and the simulated experiments supported the approach.
They wrote the paper entitled, ‘Dielectric-Fibre Surface Waveguides
for Optical Frequencies’ and submitted it to the Proceedings of
Institute of Electrical Engineers. After the usual review and revision,
it appeared in July 1966 – the date now regarded as the birthday of
optical fiber communication.
4. The paper
The paper started with a brief discussion of the mode properties in a
fiber of circular cross section.
The paper then quickly zeroed in on the material aspects, which were
recognized to be the major stumbling block. At the time, the most
transparent glass had a loss of 200 dB/km, which would limit
transmission to about a few meters – this is very obvious to anyone
who has ever peered through a thick piece of glass. Nothing can be seen.
But the paper pointed out that the intrinsic loss due to scattering
could be as low as 1 dB/km,which would have allowed propagation over
practical distances. The culprit is the impurities:
mainly ferrous and ferric ions at these wavelengths. Quoting from the
paper: ‘It is foreseeable that glasses with a bulk loss of about 20
dB/km at around 0.6 micron will be obtained, as the iron-impurity
concentration may be reduced to 1 part per million’. In layman terms,
if one has a sufficiently ‘clean’ type of glass, one should be able
to see through a slab as thick as several hundred meters. That key
insight opened up the field of optical communications.
The paper considered many other issues:
? The loss can be reduced if the mode is chosen so that most of the
energy is actually outside the fiber.
? The fiber should be surrounded by a cladding of lower index (which
became the standard technology).
? The loss of energy due to bends in the fiber is negligible for bends
larger than 1 mm.
? The losses due to non-uniform cross sections were estimated.
? The properties of a single-mode fiber (now a key technology
especially for long distance and high data rate transmission) were
analyzed. It was explained how dispersion limits bandwidth; an example
was worked out for a 10 km route – a very bold scenario in 1966.
It may be appropriate to quote from the Conclusion of this paper:
The realization of a successful fiber waveguide depends, at present,
on the availability of suitable low-loss dielectric material. The
crucial material problem appears to be one which is difficult but not
impossible to solve. Certainly, the required loss figure of around 20
dB/km is much higher than the lower limit of loss figure imposed by
fundamental mechanisms.
Basically all of the predictions pointed accurately to the paths of
developments, and we now have 1/100 of the loss and 10,000 times the
bandwidth then forecast – the evolutionary proposal in the 1966 paper
was in hindsight too conservative.
5. Convincing the world
The substance of the paper was presented by Dr Kao at an IEE meeting
in February 1966. Most of the world did not take notice – except for
the British Post Office (BPO) and the UK Ministry of Defense, who
immediately launched major research programs. By the end of 1966,
three groups in the UK were studying the various issues involved: Kao
himself at STL; Roberts at BPO; Gambling at Southampton in
collaboration with Williams at the Ministry of Defense Laboratory.
In the next few years, Dr Kao traveled the globe to push his idea: to
Japan, where enduring friendships were made dating from those early
days; to research labs in Germany, in the Netherlands and elsewhere to
spread his news. He said that until more and more jumped on the
bandwagon, the use of glass fibers would not take off. He had
tremendous conviction in the face of widespread skepticism. The global
telephony industry is huge, too large to be changed by a single person
or even a single country, but he was persistent and his enthusiasm was
contagious, and slowly he converted others to be believers.
The experts at first proclaimed that the materials were the most
severe of the intrinsic insurmountable problems. Gambling wrote that
British Telecom had been ‘somewhat scathing’about the proposal
earlier, and Bell Labs, who could easily have led the field, simply
failed to take notice until the proven technology was pointed out to
them. Dr Kao visited many glass manufacturers to persuade them to
produce the clear glass required. He got a response from Corning,
where Maurer led the first group that later produced the glass rods
and developed the
techniques to make the glass fibers to the required specifications.
Meanwhile, Dr Kao continued to pour energy into proving the
feasibility of glass fibers as the medium for long-haul optical
transmission. They faced a number of formidable challenges. The first
was the measurement techniques for low-loss samples that were
obtainable only in lengths of around 20 cm. The problem of assuring
surface perfection was also ormidable. Another problem is end surface
reflection loss, caused by the polishing process. They faced a
measurement impasse that demanded the detection of a loss difference
between two samples of less than 0.1%, when the total loss of the
entire 20 cm sample is only 0.1%. An inexact measurement would be
meaningless.
In 1968 and 1969, Dr Kao and his colleagues Davies, Jones and Wright
at STL published a series of papers on the attenuation measurements of
glass that addressed the above problems. At that time, the measuring
instruments called spectrophotometers had a rather limited sensitivity
– in the range of 43 dB/km. The measurement was very difficult: even
a minute contamination could have caused a loss comparable to the
attenuation itself, while surface effects could easily be ten times
worse. Dr Kao and the team assembled a homemade single-beam
spectrophotometer that achieved a sensitivity of 21.7 dB/km. Later
improvements with a double-beam spectrophotometer yielded a
sensitivity down to 4.3 dB/km.
The reflection effect was measured with a homemade ellipsometer. To
make it, they used fused quartz samples made by plasma deposition, in
which the high temperature evaporated the impurity ions. With the
sensitive instrument, the attenuation of a number of glass samples was
measured and, eureka, the Infrasil sample from Schott Glass showed an
attenuation as low as 5 dB/km at a window around 0.85 micron – at
last proving that the removal of impurity would lower the absorption
loss to useful levels.
This was really exciting because the low-loss region is right at the
gallium-arsenide laser emission band. The measurements clearly pointed
the way to optical communication –compact gallium-arsenide
semiconductor lasers as the source, low-cost cladded glass fibers as
the transmission medium, and silicon or germanium semiconductors for
detection. The dream no longer seemed remote. These measurements
apparently turned the sentiments of the research community around. The
race to develop the first low-loss glass fiber waveguide was on.
In 1967, at Corning, Maurer’s chemist colleague Schultz helped to
purify the glass.
In 1968, his colleagues Keck and Zimar helped to draw the fibers. By
1970, Corning had produced a fiber waveguide with a loss of 17 dB/km
at 0.633 micron using a titanium-diffused core with silica cladding,
using the Outside Vapor Deposition (OVD) method. Two years later, they
reduced the loss to 4 dB/km for a multimode fiber by replacing the
titanium-doped core with a germanium-doped core.
Bell Labs finally got on the bandwagon in 1969 and created a programme
in optical fiber research after having been skeptical for years. Their
work on hollow light pipes was finally stopped in 1972. Their
millimeter wave research programme was wound down and eventually
abandoned in 1975.
It was during this time of constant flying out to other places that
this cartoon joke hit home:‘Children, the man you see at the
breakfast table today is your father!’
We saw him for a few days and off he went again. Sometimes he flew off
for the day for meetings at ITT Corp headquarters in New York. I would
forget he had not left to go to the office and would phone his
secretary to remind Charles to pick up milk or something on his way
home.
His secretary was very amused:‘Mrs Kao, don’t you know your husband
is in New York today!’
6. Impact on the world
Since the deployment of the first-generation, 45-megabit-per-second
fiber-optic communication system in 1976, the transmission capacity in
a single fiber has rapidly increased a million fold to tens of
terabits per second. Data can be carried over millions of km of fibers
without going through repeaters, thanks to the invention of the
optical fiber amplifier and wavelength division multiplexing. So that
is how the industry grew and grew. The world has been totally
transformed because of optical fiber communication. The telephone
system has been overhauled and international long distance calls have
become easily affordable.
Brand new mega-industries in fiber optics including cable
manufacturing and equipment, optical devices, network system and
equipment have been created.
Hundreds of millions of kilometers of glass fiber cables have been laid,
in the ground and in the ocean, creating an intricate web of
connectivity that is the foundation of the world-wide web.
The Internet is now more pervasive than the telephone used to be. We
browse, we skype, we blog, we go onto you-tube, we shop, we socialize
on-line. The information revolution that started in the 1990s could
not have happened without optical fibers.
Over the last few years fibers are being laid all the way to our homes.
All-optical networks that are environmentally green are contemplated.
The revolution in optical fiber communication has not ended – it
might still just be at the beginning.
7. Conclusion
The world-wide communication network based on optical fibers has truly
shrunk the world and brought human beings closer together. I hardly
need to cite technical figures to drive this point home. The news of
the Nobel Prize reached us in the middle of the night at 3 am in
California, through a telephone call from Stockholm (then in their
morning) no doubt carried on optical fibers; congratulations came
literally minutes later from friends in Asia (for whom it was evening),
again through messages carried on optical fibers. Too much information
is not always a good thing: we had to take the phone off the hook that
night in order to get some sleep!
Optical communication is by now not just a technical advance, but has
also caused major changes in society. The next generation will learn
and grow up differently; people will relate to one another in
different ways. Manufacturing of all the bits and pieces of a single
product can now take place over a dozen locations around the world,
providing huge opportunities for people especially in developing
countries. The wide accessibility of information has obviously led to
more equality and wider participation in public affairs.
Many words, indeed many books have been written about the information
society, and I do not wish to add to them here – except to say that
it is beyond the dreams of the first serious concept of optical
communication in 1966, when even 1 GHz was only a hope.
In conclusion, Charles and I want to thank the Professors at The
Chinese University of Hong Kong, namely: Professor Young, Professor
Wong, Professor Cheung and Professor Chen for their support in
compiling this lecture for us. Charles would like to thank ITT Corp
where he developed his career for 30 years and all those who climbed
on to the bandwagon with him in the early days, as without the legions
of believers the industry would not have evolved as it did.
Charles Kao planted the seed; Bob Maurer watered it and John
MacChesney grew its roots.
(XYS20091210)
https://blog.sciencenet.cn/blog-266190-278611.html
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