A Brief History of the Historical Fiber Optic
History of optical fiber: The optical systems of communication, exist for more than 2 centuries, when the “Optical Telegraph” was invented by the French engineer Claude Chappe in 1790, His system consisted of a series of traffic lights mounted on towers in those that an operator transmitted messages from one tower to another.
From then on, like all processes, I go through a series of small discoveries and advances. And it was not until 1960 that the laser was invented. On July 22, 1960, An Electronics magazine published Theodore Maiman’s first laser demonstration.
The optical fibers attracted attention, because they were similar in theory to a waveguide with plastic dielectric. In 1961, Elias Snitzer, an American optician working with Hicks at Mosaic Fabrications (later Galileo Electro-Optics), demonstrated this similarity by manufacturing fibers with small cores that carried light in the manner of a waveguide.
In the ITT STL laboratory A small group of researchers did not rule out the usefulness of fiber so easily, a team from Standard Telecommunications Laboratories, initially led by Antoni E. Karbowiak, devoted themselves to studying optical waveguides for communications. Karbowiak soon joined a young Shanghai-born engineer, Charles K. Kao.
Kao had to investigate the attenuation of the fiber. His research convinced him that the high loss of the first fibers was due to impurities, and not to the silica of the glass itself. In the middle of this investigation, in 1964, Karbowiak left STL and Kao had to replace him as research director of Optical Communications. Kao worked on a proposal for long-distance communications with single-fiber fibers. Convinced that fiber losses could be reduced below 20 decibels per kilometer.
The Corning era in the history of fiber optics
It took four years to reach the goal set by Kao of 20 dB / km, and the route of success was demonstrated differently than many expected. Most research groups tried to purify glass compounds, which were used by standard optics, which are easy to melt and stretch and turn into fibers. In Corning Glass Works (now Corning Inc.), Robert Maurer, Donald Keck and Peter Schultz, began to work with fused silica, a material that can be manufactured extremely pure, but this has a high melting point and a low refractive index . They tested with a preformed and made deposits of purified materials, from the vapor phase, carefully adding controlled levels of dopants, to obtain the core with a refractive index slightly higher than that of the coating, without a dramatic elevation of the attenuation. In September of 1970, the announcement made that single-mode fibers had been obtained, with attenuation at 633-nanometers below 20 dB / km. The fibers were fragile, but the tests confirmed the low loss.
Corning’s breakthrough was among the most dramatic of many developments that opened the door to fiber optic communication. In the same year of 1970, the Bell laboratory and a team at the Ioffe Physical Institute in Leningrad (now St. Petersburg), manufactured the first laser diodes capable of emitting continuous waves at room temperature. During the following years, fiber losses dropped dramatically, due mainly to improve manufacturing methods and the change in wavelength, to the points where the fibers have essentially low attenuation.
The first applications, the non-displaced single-mode fiber and Mass manufacturing (History of optical fiber)
The first monomódos fibers had nuclei of several micrometers of diameter, and at the beginning of the years 70 this fact caused annoyance to the scientists. They doubted that it might be possible to achieve the tolerance necessary to effectively capture the light from the sources within the tiny cores, or achieve efficient splices or connectors. Not satisfied with the low bandwidth of the step-index multimode fiber, they concentrated on the multi-mode fibers with a gradual index-refractive between the core and the coating, and core diameters of 50 or 62.5 micrometers. A milestone that is important to point out is that achieved by MacChesney and his colleagues at the Bell Laboratories who achieved in 1974 the modified chemical vapor deposition process MCVD that made possible the mass manufacture of high quality optical fiber.
The first generation tested in the field of telephony was in 1977, fibers were used to transmit light to 850 nanometers of the laser diodes of gallium-aluminum-arsenide.
These early generations of systems could transmit light to several kilometers without repeater, but were limited by losses of approximately 2 dB / km. A second generation soon appeared, using the new InGaAsP lasers that emitted at 1.3 micrometers, where the fiber attenuation was as low as 0.5 dB / km, and the pulse dispersion reduced to 850 nm.
At the beginning of the 1980s, carriers began their construction of national networks with single-mode fiber at 1300 nm.
In 1983, MCI, one of the largest long distance companies in the United States, was the first to build a National Fiber Optic Network in that country.
The displaced dispersion fiber and the Second Fiber revolution (History of optical fiber)
In the late 1980s, systems tended to operate at longer wavelengths. The Dispersed Fiber of Dispersion (DSF) was introduced in 1985, and heralded a new era in optical communications. By linking the minimum attenuation in the 1,550-nm window with zero dispersion at the same wavelength, whereby higher data rates could be carried over greater distances. In the first years of the 90s, erbium doped fiber (EDFA) appears, this is considered by many as the second revolution in fiber optic communication. This technology not only exceeded the speed limitation for electronic regeneration and allowed longer stretches; it allowed the WDM to be the dominant transmission method until today.
When the deployment of these new technologies began, it became clear that the same attribute that had made the displaced dispersion fiber so attractive caused inconvenience to WDM demands. The extra power that had to transport the fiberglass by the use of several amplifiers for each wavelength resulted in non-linear effects in the transmission.
One of the first and most damaging effects that appear is the effect of the four wave mix (FWM). In FWM, multiple wavelengths combine to create new wavelengths that can potentially interfere with transmission. The effect is more pronounced when the dispersion is close to zero.
The development of the non-zero dispersion fiber industry (NZDSF) was a direct response to the non-linear effects of propagation. The wavelength of zero dispersion is changed outside the operation window, thus introducing a small but finite amount of dispersion in order to reduce the effects of FWM.
The first commercially available NZDSF cables with a large effective area appear in 1998. By increasing the effective area of the field mode within the fiber,, and, hence, the non-linear effects can be reduced. The technical benefits are immediate: the power management capacity is higher, the signal-to-noise ratio is higher, and the space between amplifiers is higher
The New Revolution Just as erbium amplifiers signified a significant leap forward in fiber-based optical communications, optical Scwitch and routers at Sopto have been the spark for a new revolution in fiber optics. Let us be alert to these changes that have as sole objective to reduce the cost of transmission by channel.