Although, as previously mentioned, the main operation
regime of MWP filters is based on using incoherent sources,
several works [45]–[50] have reported and experimentally
demonstrated that it is possible to overcome the limitations that
source coherence imposes over the operation of MWP filters.
The use of coherent laser sources is interesting as higher input
powers can be injected into the filter thus reducing the RF link
losses. In the context of MWP filtering, a coherent source is that
having a coherence time (i.e., inverse of its linewidth) much
longer that the basic delay between adjacent samples. If such
sources are employed, then optical interference due to mechanical
and environmental fluctuations can severely compromise
the filter performance. An interesting technique is based on