
dispersive spreading. Instead, the observed penalty is attributed to the use of a
single-phase modulator in counterphasing pump scheme and nonideal suppression
of the idler spectral broadening.
20.11 FUTURE PROSPECTS
Clearly, there are still challenges to be met by all-optical signal processing devices
to be fully viable in high bit rate systems. A key issue is the required operating
peak power. For self-activated devices (where the signal itself drives the device)
this is absolutely critical, but even for externally pumped devices (such as for
FWM), it is still important. Devices based on kilometer scale lengths of HNLF are
arguably already in this ...