For multiplexed optical channel the essential parts are multiplexer and demultiplexer
modules. With high speed digital electronics technologies 10 Gbps modules are on sale
and 40 Gbps module is under development. Beyond 100 Gbps, the technical challenge
with high speed electronics is steeper, thus the introduction of all optical switches together
with optical beam combiners and splitters has been investigated (0-TDM).
There was a historic jump in high speed communication research in 1996, when the
transmission of 1 Tbps or higher signal flow through one fiber was reported by 4 groups
(Fujitsu, Lucent, NEC, N"). Realization of lThps throughput by NTT group was achieved
by 10 wavelength channels of 100 Gbps TDM codes. In 1998, NTT group reported a single
wavelength 640 Gbps transmission experiment over 80 km with 250 fs pulse train. The
NOM switch with dispersion flattening fiber was used as the demultiplexer switch, thus
an extension toward multiple wavelength operation will be feasible.
Presently sales of WDM system is steadily growing, with the positive effect on WDM
related component production in terms both on quantity and price. The ambitious 0-TDM
will play a major role when the conventional WDM technology will reach saturation.
Most recently at OFC'99 a trial transmission experiment of 3 Tbps (160 Gbps x 19
wavelength) over 40km span by OTDWDM combination, and an experiment,of 640 Gbps
over 7200km stretch by TDWDM were reported.