
couplers and delay interferometers can be controlled by heaters, which heat one
Mach–Zehnder branch. The devices are periodical filters and their free spectral
range (FSR) depends on the amount of delay in the delay interferometers. Such
devices have been designed and applied some years ago for dispersion compensa-
tion [11]. Due to their periodicity, they can be used for simultaneous multichannel
equalization if the FSR matches the WDM channel grid, but the WDM grid could
also be adapted to the FSR of the device as shown in Ref. [58].
In the left part of Figure 5.8, the optical spectrum and eye diagram of a 107-Gbit/s
NRZ modulated signal are shown. ...