Shulou(Shulou.com)11/24 Report--

In 1966, Chinese scientist Charles K.C.Kao, who works for British Standard Telecommunications Experimental Co., Ltd., together with his colleague George Hawkham (G.A.Hockham), published a paper entitled "Optical Frequency dielectric Fiber Surface waveguides".

In the title of the paper, they clearly pointed out that as long as the purity of glass fiber is solved (reducing impurities), the attenuation of optical signal in glass fiber can be reduced.

When the attenuation rate drops to 20 db/km, this glass fiber can be used for practical communication.

The paper written by Charles Kao, who is doing experiments, was later regarded as the foundation work of optical fiber communication theory. It not only opens the door of the optical fiber era, but also changes the trend of human communication technology.

Now we all know that this paper is of great significance. But in fact, at the beginning of the publication of the paper, it was not recognized by the industry.

At that time, no one believed the conclusion of Charles Kao. Everyone agrees that the "glass without impurities" envisioned by Charles Kao does not exist.

To prove his theory, Kao visited glass factories around the world to try to seek cooperation.

However, all of these factories rejected Kao. They do not intend to conduct in-depth research because such research is "meaningless and costly".

At the end of 1966, things took a turn for the better.

An engineer named William Schaefer (William Shaver), visiting the Post Office Research Laboratory in London, England, saw the optical fiber communication project introduced by the laboratory and became very interested.

The company that William Schaefer works for is not an ordinary company, but Corning Glass Works, the oldest glass manufacturer in the United States.

Corning Company was founded in 1851.

It is said that they made the glass light bulb that Edison invented.

After returning to the United States, William Schaefer reported his experience to the company's senior management, and strongly recommended that the company conduct optical fiber research.

William Schaefer's suggestion was taken seriously by the senior management of Corning. Soon, they quietly launched the research and development of high-purity fiberglass.

Bill Armstrong (Bill Armistead), Corning's director of research and development, is in charge of the work.

Bill Amstead called in the company physicist Robert Maurell (Robert Maurer) and assigned him two new young researchers (chemist Peter Schultz and experimental physicist Donald Keck) to form a three-member team.

From left: Donald Keck (Donald Keck) Robert Maurer (Robert Maurer) Peter Schultz (Pete Schultz), as the team leader, Robert Maurer is a legendary figure.

Born in 1924, Robert Maurell fought in World War II and won the Purple Heart as a young man. After the war, he returned to college to earn a doctorate in cryogenic physics from the Massachusetts Institute of Technology and joined Corning (1952).

It is worth mentioning that in December 1956, he published a theoretical paper on "Glass is a Frozen liquid" published in the Journal of Chemical Physics, which was quoted by Charles Kao in his classic paper, which was regarded as the earliest intersection between the two.

After the three-member team officially launched the research, they found that they were facing a huge challenge.

At that time, the attenuation rate of the glass fiber with the highest purity was about 1000 dB / km. To reduce this value to 20 dB / km is not a 50-fold relationship, but an astonishing 10 to the 98th coefficient relationship.

Note: dB=10*lg (A / B), which indicates the ratio of two numbers (An and B). When An is twice as large as B, it is 3dB. When An is ten thousand times that of B, it is 40dB. When An is 1 million times that of B, it is 60dB.

For them, there are two feasible starting plans: first, the use of a large number of high-purity optical glass. Second, fuse quartz (SiO2, silica), because quartz can achieve high purity.

The first is a more mature scheme, which was also chosen by most of the peers at that time. But Robert Maurell went his own way and chose the second option.

"if what you do is different from what other people do, you have two advantages," he recalled afterwards. "first, you may succeed where they fail. Second, if you fail, you will collect information that they have not collected."

Silicon dioxide is a material with high purity. However, its melting temperature is extremely high, requiring 1650 ℃. Ordinary ovens can't reach this temperature at all.

After some investigation, Robert Maurell called in Dr. Frank Frank Zimar, a doctor of chemistry, for help.

Frank Zima built an oven for Corning's early semiconductor project that could achieve temperatures of 2000 °C.

With the help of Frank Zima, Robert Maurell's team pulled out the first experimental single-mode fiber based on titanium-doped silica in 1967. After testing, the attenuation of this fiber is still very high, but it has been greatly improved compared with before. This boosted the confidence of the research team.

Later, after repeated attempts, the research team gradually mastered the drawing skills of optical fiber preforms, as well as the treatment of soot deposits and other key technologies. The attenuation rate index of the optical fiber manufactured by them has been continuously improved, gradually approaching the theoretical value.

The research progress of the three-member group is strictly kept secret by Corning. Until May 11, 1970, Corning applied for two patents based on the results achieved.

The first patent is a "fused quartz optical waveguide" by Robert Maurell and Peter Schultz for fibers with pure quartz cladding and doped quartz cores.

The second patent, Donald Keck and Peter Schultz's "method of producing optical waveguide fibers", covered what became known as the internal vapor deposition (IVD) process.

On July 22, 1970, the research team pulled six optical fibers from six titanium-doped preforms with different components.

On August 7, they tested the fibers. When they tested a 29-meter-long optical fiber, they got an amazing attenuation value of 17 dB/km. This is the first time in history to achieve the paper goal of 20 dB / km.

Donald Keck excitedly recorded the number in his notebook and wrote "Whoopee". The words.

The optical fiber length of 29 meters is short, which may affect the accuracy of the test results. In order to be more rigorous, they pulled out another 210-meter optical fiber on August 21 and tested it.

When Donald Keck's he-ne laser entered the fiber core, he was surprised to see a very bright red flash. He realized that this was a Fresnel reflection from the far end of the optical fiber. At this point, he recorded the test results of the optical fiber attenuation rate-16.9 dB/km.

Finally, they can breathe a sigh of relief. The world's first low-loss experimental optical fiber in line with the theory was officially born.

The research team and their finished optical fiber (lower left corner) Robert Maurer flew to London at the end of September 1970 and announced his team's research results at the "guided Wave Trunk Communications" conference sponsored by the British Society of Electrical Engineers. Caused a sensation throughout the industry.

Later, the British Post Office Laboratory and the Standard Telecommunications Laboratory specifically tested their optical fiber to verify their results.

After Corning's optical fiber was successfully developed, it was not immediately put on the market for commercial use. Because their optical fiber uses titanium-doped core, there are still some technical defects.

Two years later, in June 1972, Corning used germanium-doped cores instead of titanium-doped cores and external vapor deposition (OVD) to produce a multimode fiber with a loss as low as 4 dB/km.

This optical fiber not only has lower attenuation, but also is more practical and the manufacturing process is simpler.

Peter Schultz (1972), who is using OVD method to make germanium-doped fiber preform, later, because of the economic recession, Corning encountered some problems in its development, which affected their commercial promotion of optical fiber technology.

In order to raise funds, with the support of Amory Houghton, chairman and chief executive of Corning, Chuck Chuck Lucy, head of Corning's optical fiber business, negotiated with a number of communications companies and signed joint development agreements to share development costs.

These agreements speed up the commercial landing of optical fiber technology. In 1976, the American company AT&T installed the world's first experimental optical fiber communication system in Atlanta, which is about 1.25 miles (about 2000 meters) long.

Three years later, in 1979, Nippon Telegraph and telephone Company (NTT) developed a very low loss quartz fiber of 0.2dB / km. This attenuation value is basically close to the theoretical limit of scattering.

In 1980, the Lake Plucid Winter Olympic Games used optical fiber cable to transmit TV signals for the first time, which was a great success.

The rest of the story should be familiar to everyone.

In the 1980s and 1990s, optical fiber technology rose rapidly and became an important transmission medium in wired communication. In the 21st century, optical fiber has completely replaced metal cable and become the backbone base of the whole communication network. The amount of data that can be transmitted by a single optical fiber has already exceeded the TB / s level.

Today, the annual global demand for optical cable is more than 500 million core kilometers. These optical fibers transmit huge amounts of data, support the development of the whole society, and make great contributions to the progress of human civilization.

This article comes from the official account of Wechat: fresh Jujube classroom (ID:xzclasscom), author: Xiaozaojun

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