"Introduction". In: Fiber-Optic Communication Systems

200 CHAPTER 5. LIGHTWAVE SYSTEMS

Table 5.3 Commercial transatlantic lightwave systems

System Year Capacity L Comments

(Gb/s) (km)

TAT– 8 1988 0.28 70 1.3μm, multimode lasers

TAT– 9 1991 0.56 80 1.55μm, DFB lasers

TAT–10/11 1993 0.56 80 1.55μm, DFB lasers

TAT–12/13 1996 5.00 50 1.55μm, optical amplifiers

AC–1 1998 80.0 50 1.55μm, WDM with amplifiers

TAT– 1 4 2001 1280 50 1.55μm, dense WDM

AC–2 2001 1280 50 1.55μm, dense WDM

360Atlantic-1 2001 1920 50 1.55μm, dense WDM

Tycom 2001 2560 50 1.55μm, dense WDM

FLAG Atlantic-1 2001 4800 50 1.55μm, dense WDM

over 117 km at 40 Gb/s per channel while using all three bands simultaneously [50].

5.3.3 Undersea Lightwave Systems

Undersea or submarine transmission systems are used for intercontinental communi-
cations and are capable of providing a network spanning the whole earth [51]–[53].
Figure 1.5 shows several undersea systems deployed worldwide. Reliability is of ma-
jor concern for such systems as repairs are expensive. Generally, undersea systems are
designed for a 25-year service life, with at most three failures during operation. Ta-
ble 5.3 lists the main characteristics of several transatlantic fiber-optic cable systems.
The first undersea fiber-optic cable (TAT–8) was a second-generation system. It was
installed in 1988 in the Atlantic Ocean for operation at a bit rate of 280 Mb/s with a re-
peater spacing of up to 70 km. The system design was on the conservative side, mainly
to ensure reliability. The same technology was used for the first transpacific lightwave
system (TPC–3), which became operational in 1989.
By 1990 the third-generation lightwave systems had been developed. The TAT–
9 submarine system used this technology in 1991; it was designed to operate near
1.55μm at a bit rate of 560 Mb/s with a repeater spacing of about 80 km. The increas-
ing traffic across the Atlantic Ocean led to the deployment of the TAT–10 and TAT–11
lightwave systems by 1993 with the same technology. The advent of optical amplifiers
prompted their use in the next generation of undersea systems, and the TAT–12 sub-
marine fiber-optic cable became operational by 1996. This fourth-generation system
employed optical amplifiers in place of optoelectronic regenerators and operated at a bit
rate of 5.3 Gb/s with an amplifier spacing of about 50 km. The bit rate is slightly larger
than the STM-32-level bit rate of 5 Gb/s because of the overhead associated with the
forward-error-correction technique. As discussed earlier, the design of such lightwave
systems is much more complex than that of previous undersea systems because of the
cumulative effects of fiber dispersion and nonlinearity, which must be controlled over
long distances. The transmitter power and the dispersion profile along the link must be