
where T is the bit duration, we find
s
=
P
s
T
hf
= N
s
;
(3.35)
where N
s
= P
s
T= hf means the number of photons per bit.
However, the homodyne phase-diversity rece iver can generate the complex
amplitude given by Eqn (3.20) at the baseband. Therefore, the mean square of
the signal photocurrent is given as
jI
c
ðtÞj
2
= R
2
P
s
P
LO
. When reconstructing the
complex amplitude, we need to add shot noises due to the LO powers of P
LO
=2
from the two ports. The receiver bandwidth at the baseband is B=2 = 1=2T; there-
fore, the total noise current is given as eP
LO
B. We can thus obtain the SNR
s
= P
s
=hfB = N
s
, which is the same as the heterodyne receiver. Even when
the polarization ...