Light travels through glass. Otherwise, you wouldn’t have any windows in your home, and skyscrapers might be wrapped in concrete skins. Light is also abundant, thanks to the sun and stars, luminous gases, and spark-generating electricity. Communicating with light has primitive beginnings.
Glass, which is easily made from sand-born silica, flint, spar, and other silicious materials, is also highly abundant. The geologic glass, obsidian, was first used thousands of years ago to form weapons and jewelry. Man-made glass objects date back into the Mesopotamian region, as early as about 1700 BC. The Romans made glass in 1 AD and spurred rapid development and expansion of the art in the Mediterranean region. Therefore, glass making has been around awhile.
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Of the many types of glass, optical glass made its 1590 AD debut in early glass telescopes in the Netherlands. Edison used glass for his invention of the light bulb and its first public demonstration on December 31, 1879. Glass was used for train lights shortly after. Window glass and glass television tubes were used extensively in the 1900s. Optical glass is also the basis of focusing and pulling an image’s attributes into a camera body to excite
photographic film. As a kid, you might recall a spyglass with a 90-degree bend that you could use to “spy” around the corner of a building. It used an angled mirror at the bend to reflect the light from end to end. While that was a reflection of light through the air inside the spyglass, the same reflective properties work for light that is propagating through optical glass or optical fiber.
If you had a cylindrical seven-foot-tall hallway of pure glass wrapped in a flexible mirror- like cladding and then took a flashlight and beamed it at the end of the glass hallway, the beam would travel inside of the glass to one edge of the glass hallway, reflect off the mirrored cladding, and continue bouncing back and forth until it reached the other end— almost as visibly bright as if the flashlight itself had passed completely through. Now, in secret agent fashion, if you switch the flashlight on and off in random patterns such as Morse code, someone on the other end can decipher this timed sequence of light and dark flashes, checking it against a Morse decoder ring to understand what is being communicated through light pulses. This rudimentary description of communicating with light in glass is the elementary principle behind the use of fiber optics.
For the purposes of telecommunications, optical-grade glass is reduced to long, thin strands of extremely pure glass, known as optical fiber. The glass strand is so thin that it takes on the flexible properties of a human hair. The light that is used to pass through an optical fiber is nonvisible light, from the infrared portions of the electromagnetic spectrum. The infrared light’s wavelength is scientifically measured in nanometers. Frequency is another property of light waves, and for the infrared portion of the spectrum, the frequency is measured in TeraHertz. The light is generated and focused through very small lasers to concentrate the light before it enters one end of an optical fiber.
Pushing photons through optical fiber is a combination of technologies that improves many-fold over the traditional excitation of electrons through copper-wire cable. Also with optical, the raw materials are more abundant and manufacturing improvements are making it ever cheaper, competing with copper cables of equivalent length. With optical, the diameters are smaller, the information-carrying capacity is higher, there’s less interference and signal loss, fewer errors, less power expended, and much lighter handling weight. By improving speed, capacity, and clarity, fiber optics provides service-improving values that are useful in many industries and superior for use in communications.
In 1970, the world’s first low-loss, silica optical fiber for communications was created at Corning Inc., in Corning, New York. Corning was a high technology manufacturer of glass, and many of the company’s achievements in the field, even as early as the 1934 invention of fused silica, became part of the success story of producing optical fiber that was suitable for long-distance communication with low loss of photonic energy. By 1978, Corning had
perfected the process of creating single-mode fiber in volume. Today, there are multiple types and grades of fiber, often referred to as application-specific fiber, each specially designed for a particular deployment such as long haul, metropolitan, undersea, or access and premise. By the early 1980s, the beginnings of telecom deregulation prompted new entrants to make the first commercial use of optical fiber in backbone sections of their new- technology networks to alleviate burgeoning, traffic choke points. These new competitors advertised the technical advantages of their optical backbone networks with an appeal to improved clarity and capacity.
Like a rock thrown into a pond, optical fiber deployment has steadily followed these bandwidth choke points, in ripple-like effect, from the center of these national networks ever closer to the communicating end user. Today, the choke points have been pushed into the last few miles of consumer access. While cable TV and telephony companies have been at work extending the performance of their copper plants, the probability is very high that fiber optics to the business, the desk, and home will become one of the shining stars of broadband opportunity over the next few decades.
Erbium-doped fiber amplifiers in the 1990s created another optical leap forward. Not only did this technological advance increase the distance that light could travel before needing optical-to-electrical-to-optical (OEO) regeneration, but it also unleashed the optical fiber to use multiple wavelengths, or lambdas, of infrared light. It’s doubtless you’ve seen how light refracts through a prism to form several colors of light. This principle is at the basis of optical wavelength division multiplexing (WDM) and allows a single optical fiber to carry more colors or wavelengths of communication per fiber, currently up to about 640 distinct lambdas or channels per strand. More are on the way. This, in effect, has multiplied the information-bearing capacity of a fiber strand by hundreds of times over. It creates a price/ performance improvement of sizable proportions that helps future-proof a fiber network. It also makes available an opportunity to lease or purchase bandwidth by the lambda instead of by the whole fiber strand. With fiber span distances stretching ever further between OEO regenerations, new deployments significantly reduce capital costs and operating expenses, shortening the return on investment timeframe and improving the profitability of the network over the system’s life.
Fiberless optics technology is emerging as another usage of optics through air that is well- suited for high data rates in urban high-rise developments. Using optical and holographic technology with self-focusing, small aperture dishes, wireless optics provide a quick and cost-effective way to connect downtown buildings without cutting the streets or floors for cable passage.
Optical switching and routing is fanning the flames of optical advancement by seeking to remove the electrical-to-optical tax that is paid where optical regeneration requires conversion to electrical in order to be traffic-switched or regenerated. Based on wavelength manipulation technologies from prisms to bubbles to minimirrors to waveguides, this developing field has already produced commercial products that combine, split, and redirect lambdas to create optical cross-connects and add/drop multiplexers (ADMs). The
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equipment does this without converting the bit stream to electrical until it’s handed off to the last mile. With such an abundance of lambdas and optical switching in your grasp, you might indeed circle back to the concept of circuit-switched networks (voice networks), only this time where they are optically, or rather, lambda–switched.
Optics as a technology for communications is white hot. In fact, optics is increasingly being complemented with IP to reduce complexity and streamline offerings with familiar technol- ogies. In a few short years, there’ll be optical communication available anywhere that infor- mation is generated or consumed. With more than 300 million kilometers of optical fiber deployed worldwide, lambda switching at the meet points and free-space (through the air) optics filling the gaps, optical is at the heart of the fibersphere and belongs on the short list of technological winners.