
8.6 ROADM/WADD ARCHITECTU RE—THINKING
INSIDE THE BOX
Many WADD designs suitable for use in the ROADM framework shown in Figure
8.2 can be grouped into two classes: the parallel WADD, in which an assembly of
space switches is sandwiched between the DMUX and MUX components [Figure
8.5(a), 8.5(b), or 8.5(c)]; and the serial WADD composed of cascaded tunable
filters (Figure 8.11). However, years of active ingenuity have also produced
proposals or demonstrations of a wide variety of hybrid designs and unique
reconfigurable components. Rather than try to catalog them all here, we will
concentrate on three common designs that are commercially available.
8.6.1 ...