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History of the Atlantic Cable & Undersea Communications
from the first submarine cable of 1850 to the worldwide fiber optic network

1982 SL Lightguide Cable Sea Trials

Landline fiber optic communications cables first went into service in 1977, but, as with copper cables, ensuring reliable operation using optical fiber cables under water was a task of a higher magnitude. By the early 1980s optical fiber submarine cables were under development in Japan, Britain, France, and the USA, and a number had been successfully tested in shallow water.

In the United States, Bell Laboratories and the Simplex Wire and Cable Company jointly researched fiber optic submarine cables, and in 1978 Bell Labs manufactured a prototype, the first ever made. Bell Labs also worked with Western Electric to develop an integrated-circuit-based optical submarine repeater. By late August 1982 a length of 18.25 km of lightweight fiber optic submarine cable, type SL, had been manufactured by Simplex, and the cable and a repeater with two 274 MB/s regenerators were ready for test.

Desk display commemorating the first-ever deep-sea trials
of a lightwave communications system in September 1982.

A deep-sea trial was conducted between 31 August and 12 September 1982 using CS Long Lines. The cable and repeater were laid in an ocean depth of 5,500 metres in the North Atlantic, about 500 miles from Bermuda; the run also included a number of splices. Tests showed that transmission losses due to temperature, tension, and pressure changes were negligible, and the cable and splices survived the stresses of laying and picking up without any fiber breaks. This was significant in being the first-ever deep-sea trial of a fiber optic cable system.

The deep-sea trial was followed by further development of the components of the system. In 1985 a short SL system was installed between Gran Canaria and Tenerife in the Canary Island chain (OPTICAN), where it served as a test vehicle for its planned use in the upcoming TAT-8.

It was reported in February 1986 that “The most ambitious experiment was a cable AT&T laid last autumn, running 116 kilometres between Tenerife and Grand Canaria in the Canary Islands. After testing the system with two repeaters, engineers from the Bell Labs of AT&T intentionally broke the cable and successfully spliced in a third repeater, demonstrating that they could recover and repair TAT-8 if necessary.” (New Scientist Feb 6, 1986)

According to TE Subcom, the successor to Simplex, the cable was ready for service in 1986.

When TAT-8 was laid in 1988 it became the first optical fiber cable to span the Atlantic.

The desk display shown above commemorates the 1982 sea trial, and includes a sample of the SL fiber optic cable, a map of the test location, and (on the reverse) connection details of the cable and equipment used in the tests.

SL Cable.

Detail of core. The optical fibers
are the tiny black dots
surrounding the central wire

The central core is 2.6mm in diameter and contains twelve optical fibers embedded in elastomer and wound around the central steel wire. Steel strands act as a strength member, and these are surrounded by a continuously welded copper cylinder, which is a water and hydrogen diffusion barrier. This also carries the power for the repeaters. An outer layer of low-density polyethylene provides cable insulation and abrasion resistance.

Detail of cable and core construction

In Undersea Lightwave Communications (1986) details of the trials are given:

The sequence of operations at the test site were:

Survey of sea trial site;
Lay tail cable with splice box, repeater, and 10.4 km of active cable;
Hold in this configuration for 18 h;
Recover 10.4 km of cable;
Lay 17.5 km of active cable;
Hold in this configuration for 2 h; and
Recover active cable, repeater, and tail cable.

Technical details of the test connections

The results of the tests:

18-km cable and repeater performed as expected during laying, holding, and recovery operations in 5.5-km deep water.

Error-free transmission of 274 Mbit/s and 420 Mbit/s was demonstrated during 1-h test periods in all phases of operations.

Maximum loss change due to temperature, tension, and pressure was less than 0.1 dB under all conditions.

The cable, repeater, and splice box were recovered in original working condition.

3000 FM [fathoms] Sea Trial 1982 - SL Lightguide Cable
North Atlantic Ocean 35° 10' N, 54° 10' W

Map showing the test location:

View 1982 SL Cable Sea Trial in a larger map.
Yellow marks Bermuda; blue the location of the sea trial site.


Shimura, S., Editor: International Submarine Cable Systems, Tokyo, 1984, KDD Engineering and Consulting, Inc.

Runge, Peter K. and Patrick R. Trischitta: Undersea Lightwave Communications, New York, 1986, IEEE Press.

Last revised: 22 February, 2021

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