
integer multiple of the symbol duration to provide clean interference properties.
Due to stability reasons, one almost exclusively chooses a demodulation delay of a
single symbol period.
8
If both signal quadratures (I and Q) are to be detected, a
second interferometer with 90 shifted interference properties is typically used, in
analogy to a 90 hybrid in coherent detection.
If a phase modulation format is detected differentially, i.e., by delay demodula-
tion, one generally speaks of differential phase shift keying (DPSK), although the
word “differential” characterizes the detection technique and not the format itself.
From a strict modulation format ...