Birth of Fiber Optics (1950s–1970)

The modern era of optical fiber communications began with advances in medical imaging fibers, the invention of the laser, and a decisive theoretical insight that pure glass could guide light over long distances with acceptable loss.

Clad Fibers for Imaging

In the early 1950s researchers sought better ways to look inside the human body. In 1954 Abraham van Heel in the Netherlands and, independently, Harold Hopkins and Narinder Singh Kapany in Britain published results on flexible bundles of optical fibers that could transmit images. Van Heel’s critical contribution was the addition of a lower-refractive-index cladding around each fiber. Cladding protected the reflecting surface from contamination and reduced crosstalk between adjacent fibers.

Glass-clad fibers soon achieved losses on the order of 1 dB per meter—excellent for endoscopes a few meters long, but still roughly a thousand times too high for telecommunications over kilometers. Narinder Kapany later popularized the term “fiber optics” and contributed extensively to the field.

The Laser

A practical optical communications system also needed a suitable light source. In 1958 Charles Townes and Arthur Schawlow published the theoretical foundation for the optical maser (laser). In 1960 Theodore Maiman demonstrated the first working laser using a synthetic ruby crystal. Continuous-wave helium-neon lasers followed within months. Semiconductor diode lasers capable of room-temperature continuous operation were achieved around 1970, providing the compact, efficient sources that fiber systems would eventually require.

Single-Mode Waveguides

In 1961 Elias Snitzer at American Optical described the waveguide modes of cylindrical glass fibers and demonstrated that a sufficiently small core could support only a single mode. Single-mode operation would later prove essential for high-bandwidth, long-distance transmission because it eliminates intermodal dispersion.

Charles Kao’s Insight (1966)

By the mid-1960s most researchers considered optical fibers too lossy for communications. Charles K. Kao and George Hockham at Standard Telecommunication Laboratories in the United Kingdom took a different view. Through careful measurements of bulk glasses and existing fibers, Kao concluded that the high attenuation (often around 1,000 dB/km) was caused primarily by impurities rather than by the intrinsic properties of silica glass. In a seminal 1966 paper they argued that if impurities could be removed, fiber loss could be reduced below 20 dB/km—low enough for practical long-distance systems—and that single-mode fiber was the preferred approach.

Kao’s vision redirected research efforts worldwide. He was awarded the Nobel Prize in Physics in 2009 for “groundbreaking achievements concerning the transmission of light in fibers for optical communication.”

Corning’s Low-Loss Fiber (1970)

In August 1970 a team at Corning Glass Works—Robert Maurer, Donald Keck, and Peter Schultz—announced the first optical fiber with attenuation below 20 dB/km. They used a vapor-deposition process to create extremely pure fused silica, doping the core to raise its refractive index slightly above that of the cladding. Early fibers were fragile and operated at visible wavelengths, but the demonstration proved that Kao’s target was achievable. Subsequent improvements rapidly drove losses still lower, especially at the infrared wavelengths later used for telecommunications.

The combination of low-loss fiber and practical semiconductor lasers opened the door to the commercial optical communications systems that would emerge in the following decade.