In 1966, KCKao, a Chinese scientist working for the British Standard Telecommunications Experimental Co., Ltd. , and his colleague George Hockham (GA Hockham), jointly published a paper entitled “Optical Frequency Dielectric Fiber Surface Waveguide” .
In the paper, they clearly stated that as long as the purity of the glass fiber is solved (reducing impurities), the attenuation of the optical signal in the glass fiber can be reduced.
When the attenuation rate drops to 20 db/km , this glass fiber can be used for practical communication.
Kao doing experiments
This paper was later regarded as the foundational work of optical fiber communication theory. It opened the door to the optical fiber era and changed the direction of human communication technology.
We all know by now that the paper was significant. 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 Gao Kun’s conclusion. Everyone believes that the “glass without impurities” envisioned by Gao Kun does not exist.
In order to prove his theory, Kao visited glass factories all over the world, trying to seek cooperation.
However, these factories all rejected Gao Kun. They do not plan to conduct an in-depth study because such research is “pointless and expensive”.
At the end of 1966, things ushered in a turning point.
An engineer named William Shaver (William Shaver) visited the Post Office Research Laboratory in London, England, saw the fiber optic communication project introduced by the laboratory, and became very interested.
Corning Glass Works , the oldest glass manufacturing company in the United States .
Corning Incorporated was founded in 1851.
They are said to have made the glass bulb that Edison invented the electric light bulb.
After returning to the United States, William Shaffer reported his experience to the company’s top management, and strongly suggested that the company conduct optical fiber research.
William Shaffer’s suggestion has been taken seriously by Corning’s top management. Soon, they quietly started the research and development of high-purity glass fiber.
Leading the effort was Bill Armistead, Corning’s director of research and development .
He recruited corporate physicist Robert Maurer (Robert Maurer), assigned him two new young researchers (chemist Pete Schultz , experimental physicist Donald Keck ), and thus formed a team. 3 people research team.
As the team leader, Robert Maurer is a legendary figure.
Born in 1924, he participated in World War II when he was young and won the Purple Heart Medal. After the war, he returned to college, earned a Ph.D. in low-temperature physics from MIT, and worked for Corning (1952).
It is worth mentioning that in December 1956, he published a theoretical paper on “Glass is a frozen liquid” in the “Journal of Chemical Physics”, which was once quoted by Gao Kun’s classic paper. intersection.
After the three-person team officially started the research, they found themselves facing a huge challenge.
At that time, the glass fiber with the highest purity had an attenuation rate of about 1000 dB/km. Wanting to reduce this value to 20 dB/km is not a relationship of 50 times, but an astonishing 10 to the 98th power coefficient relationship.
Zaojun Note: dB=10*lg(A/B), which means the ratio of two numbers (A and B). When A is twice of B, it is 3dB. When A is 10,000 times that of B, it is 40dB. When A is 1 million times that of B, it is 60dB.
For them, there are two feasible starting options: First, use a large amount of high-purity optical glass. Second, fused silica (SiO2, silicon dioxide), because quartz can achieve high purity.
The first is a relatively mature solution, and it was also the solution chosen by most of the peers at that time. However, Robert Maurer took a different approach and chose the second option.
He recalled afterwards: “If you do things differently than everyone else is doing, you have two advantages. One, you may succeed where they failed. Two, if you fail, you will collect their No information was collected.”
Silica is a very pure material. However, its melting temperature is extremely high, requiring 1650°C. Ordinary ovens simply cannot reach such temperatures.
After some investigation, Robert Maurer enlisted the help of Frank Zimar, Ph.D. in chemistry .
Frank Zima once built an oven for Corning’s early semiconductor projects that could reach temperatures of 2000°C.
With the help of Frank Zima, in 1967, Robert Maurer’s group pulled the first experimental single-mode optical fiber based on titanium-doped silica. After testing, the attenuation of this fiber is still high, but it has been greatly improved compared to before. This boosted the research team’s confidence.
Later, after repeated attempts, the research team gradually mastered the drawing skills of optical fiber preforms, as well as key technologies such as the treatment of soot deposits. The attenuation index of the optical fiber they manufactured has been continuously improved, gradually approaching the theoretical value.
The research progress of the 3-member team was kept strictly confidential by Corning. Until May 11, 1970, Corning applied for two patents based on the results it had achieved.
The first patent was for “Fused Silica Optical Waveguides” by Robert Maurer and Pete Schulz for an optical fiber with a pure silica cladding and a doped silica core.
The second patent, Donald Keck and Pete Schulz’s “Method for Producing Optical Waveguide Fibers”, covered what became known as the in-house vapor deposition (IVD) process.
On July 22, 1970, the research team pulled out 6 optical fibers from 6 titanium-doped preforms with different compositions.
On August 7, they tested these fibers. When testing a 29-meter-long fiber, they obtained an astonishing attenuation value of 17 dB/km . This is the first time ever that the thesis target of 20 dB/km has been achieved.
Donald Keck excitedly recorded the number in his notebook and wrote ” Whoopee (meaning haha, expressing excitement)!”
The 29-meter fiber length is short, which may affect the accuracy of the test results. In order to be more rigorous, on August 21, they pulled out another 210-meter optical fiber and tested it.
When Donald Keck’s helium-neon laser entered the fiber core, he was surprised to see a very bright red flash. He realized it was a Fresnel reflection from the far end of the fiber. At this time, he recorded the test result of the optical fiber attenuation rate – 16.9 dB/km .
Finally, they can breathe a sigh of relief. The world’s first theoretical low-loss experimental optical fiber was officially born.
The research team and their finished fiber (bottom left)
At the end of September 1970, Robert Maurer flew to London and announced the research results of his team at the “Guided Wave Trunk Communication” conference hosted by the British Institute of Electrical Engineers, which caused a sensation in the entire industry.
Later, the British Post Office Laboratory and the Standard Telecom Laboratory specifically tested their optical fibers and verified their results.
After the successful development of Corning’s optical fiber, it was not immediately commercially available. Because their optical fiber uses a titanium-doped fiber core , there are still some technical defects.
Two years later, in June 1972, Corning replaced the titanium-doped fiber core with a germanium-doped fiber core, and used external vapor deposition (OVD) to manufacture a multimode fiber with a loss as low as 4 dB/km .
This optical fiber not only has lower attenuation, but also has stronger practicability and a simpler manufacturing process.
Pete Schulz making germanium-doped optical fiber preforms using the OVD method (1972)
Later, due to the economic recession, Corning encountered some problems in its development, which affected their commercial promotion of optical fiber technology.
Fiber Optics head Chuck Lucy, with the support of Corning Incorporated Chairman and CEO Amory Houghton, negotiated with several communications companies to sign Signed a joint development agreement to share development costs.
These agreements accelerate the commercialization of optical fiber technology. In 1976, AT&T Corporation of the United States installed the world’s first experimental optical fiber communication system in Atlanta, with a length of about 1.25 miles (about 2000 meters).
Three years later, in 1979, Nippon Telegraph and Telephone Corporation (NTT) developed an extremely low-loss silica optical fiber of 0.2 dB/km. This attenuation value is basically close to the theoretical limit of scattering.
In 1980, fiber optic cables were used for the first time to transmit television signals at the Lake Placid Winter Olympics, with 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 communications. In the 21st century, optical fibers have completely replaced metal cables and become the backbone base of the entire communication network. The amount of data that can be transmitted by a single optical fiber has already broken through the TB/s level.
Today, the global annual demand for optical cables exceeds 500 million fiber-kilometers. These optical fibers transmit massive amounts of data, support the development of the entire society, and make great contributions to the progress of human civilization.