Voices of light cross the Atlantic on glass strands

@Mark Ollig


The first transatlantic fiber-optic cable (TAT-8) transmitted telephone calls using laser light between the US, UK, and France Dec. 14, 1988.

“Welcome to this historic transatlantic crossing on a beam of light,” science fiction author Isaac Asimov said over the new fiber-optic cable during the inauguration ceremonies.

The cost of the TAT-8 project was reported to be $335 million, which is approximately $975 million in today’s dollars.

The TAT-8 story began in 1985 with AT&T’s trials of the OPTICAN system, a 66.5-mile fiber-optic Submarine Line (SL) system installed between Gran Canaria and Tenerife within the Canary Island chain.

OPTICAN tested the SL lightwave technology and fiber-optic cable for the TAT-8 system.

After sharks damaged cables in the Canary Islands, AT&T and Bell Labs created stronger cable armor to improve the reliability of the upcoming TAT-8 system.

The TAT-8 system was a collaboration of telecom companies from North America and Europe, managed by AT&T, British Telecom, and France Telecom.

AT&T’s Western Electric subsidiary manufactured the fiber-optic cable in partnership with Britain’s Standard Telephones and Cables and France’s CIT-Alcatel.

Three cable ships (CS) managed different sections of TAT-8’s installation.

The CS Vercors, a France Telecom vessel, laid the French branch of the TAT-8 cable to Penmarch, France.

The CS Alert, owned by British Telecom, was responsible for laying the UK branch of TAT-8, connecting it to Widemouth Bay, England.

The CS Long Lines, an AT&T ship, its name a reference to AT&T’s long-distance network, managed the laying of the primary transatlantic portion of the fiber-optic cable.

This large 512-foot vessel featured a 69-foot beam (its widest width) and a 29-foot draft (the depth at which it sits in the water), and it weighed approximately 11,271 tons.

It was powered by an electric turbine, reaching a top speed of 15 knots (17.3 mph), and navigated using advanced instruments like LORAN-C and gyrocompasses.

When installing the fiber-optic cable, the ship traveled at a much slower pace of one to three knots (1.15 to 3.45 mph), with a linear cable engine managing the payout speed and tension of the fiber-optic line as it entered the water.

CS Long Lines could carry about 1,800 nautical miles (2,071 miles) of fiber-optic cable in its cylindrical tanks.

Sections of the fiber-optic cable were spliced on the cable ship in clean rooms to prevent contamination.

Specialized equipment onboard the CS Long Lines, including a large crane-like gantry, allowed the crew to safely deploy the cable with a bit of slack, which helped reduce strain from ocean currents and seismic activity.

Throughout the TAT-8 installation, continuous electrical and optical tests using an Optical Time Domain Reflectometer (OTDR) ensured the fiber’s stability.

The TAT-8 system would transmit signals using a short wavelength of light, approximately 1.3 micrometers, through the hair-thin strands of single-mode fiber.

Injection lasers and photodiodes encoded the data as binary ones and zeros.

A protective armor layer surrounded the TAT-8 fiber-optic cable, which, for most of its journey across the ocean, was no thicker than a garden hose. It bundled three fiber pairs, totaling six glass strands.

The TAT-8 fiber-optic cable system supported a total capacity of 560 megabits per second, which could support 40,000 phone circuits using two active fiber pairs, each carrying 280 Mbps of traffic; the third fiber pair served as a backup.

Repeaters were installed every 25 to 43 miles along the cable, powered by high-voltage direct current (DC) from shore stations via a copper conductor within the cable.

Shore stations could also remotely monitor the performance and status of each repeater.

As the main fiber-optic cable neared Britain, a branching unit (BU) in a pressure-resistant casing on the ocean floor distributed both optical data signals and electrical power to Widemouth Bay, England, and Penmarch, France.

In December 1988, the TAT-8 fiber-optic cable system provided transatlantic phone service, connecting Tuckerton, NJ; Widemouth Bay, England; and Penmarch, France.

This first high-capacity digital link between the US and Europe showcased the benefits of fiber optics for long-distance communication, as well as the early global accessibility of the internet and the World Wide Web.

During the mid-to-late 1980s, fiber-optic technology was replacing copper telephone wires.

By 1987, the Winsted Telephone Company, where I worked, was routing its long-distance calls through the Nortel DMS-10 digital switching platform to an underground fiber-optic toll cable it had installed.

Prior to 1987, cellular and cable TV telephone services were not yet readily available, and long-distance calls in and out of Winsted relied on analog technology and a copper-paired toll cable to Howard Lake.

This toll cable, with its above-ground repeaters, was susceptible to lightning interference, causing occasional outages during storms.

The new underground fiber-optic cable was immune to electrical interference, such as lightning, ensuring reliable long-distance telephone service.

“After we switched to fiber, we hardly had any problems during storms,” said Mike Ollig, who worked with me at the telephone company.

During the early 2000s, I sometimes tested TDS Telecom’s fiber-optic network using a Tektronix OTDR.

To perform a test without interrupting customer service, I would first switch live traffic to a standby fiber pair.

The OTDR then sent pulses of light down the now-idle fiber, generating data based on the testing criteria.

The data was processed using the Tektronix FMTAP (Fiber Master Trace Analysis Program), which produced a detailed diagnostic map of the entire fiber-optic cable on my computer screen.

This map enabled me to identify everything from signal loss at a splice and microscopic flaws (microbends) to larger physical faults, such as sharp bends (macrobends).

It could even pinpoint a catastrophic fault, such as a fiber break, by detecting the massive reflection of the test light that reveals the break’s exact location.

TAT-8 was active until 2002, when newer transatlantic cables with greater capacity replaced it.

For the foreseeable future, fiber optics will remain the world’s dominant communications technology.