  We theoretically prove a multifunctional photonic differentiation (DIFF)
scheme based on phase demodulation using two cascaded linear filters. The
photonic DIFF has a diversity of output forms, such as 1st order intensity
DIFF, 1st order field DIFF and its inversion, 2nd order field DIFF, dependent
on the relative shift between the optical carrier and the filter's resonant
notches. As a proof, we also experimentally demonstrate the DIFF diversity
using a phase modulator and two delay interferometers (DIs). The calculated
average deviation is less than 7% for all DIFF waveforms. Our schemes show the
advantages of flexible DIFF functions and forms, which may have different
optical applications. For example, high order field differentiators can be used
to generate complex temporal waveforms. And intensity differentiators are
useful for ultra-wideband pulse generation.
