14.3 FIBER INFRASTRUCTURE
14.3.1 In the First-Generation, Single-Channel
Optical Systems
The first generation of commercial optically amplified undersea systems relied on
dispersion-shifted fiber (DSF). DSF has a very low chromatic dispersion at the
wavelength where the signal is transmitted (0 ps/nm.km around 1550 nm), so that
dispersion accumulation at the end of the link is contained. Soon after its introduc-
tion in laboratory experiments, it was observed that DSF was not adapted to
wavelength-division multiplexed (WDM) transmissions. As a result of nonlinea r
effects, especially four-wave mixing, detrimental channel-to-channel interactions
prohibit transmission over undersea distances over this fiber.
14.3.2 In the Early WDM Systems
This is the ...