where each CNR term corresponds to a different element of the transmission system: Notably,
CNRRIN originates from the laser diode relative intensity noise, and CNRth and CNRshot are
associated with the optical receiver. According to the insert of the Fig. 3, the CNR value in each
visual carrier, fc, should exceed 43 dB at consumer premises; otherwise, Bsnow[ phenomenon
occurs in that channel. The measured CNR in various CATV channels always exceeded 43 dB. Acomparison with 0 km transmission measurements shows that a power penalty of about 3.78 dB for
the CNR values was presented at the 25 km transmission, due to lower received power. Moreover,
a long-distance 1550 nm CATV system that transported 64 QAM signals was demonstrated [21].
This system can achieve a CNR of 30 dB after 740 km SMF transmission for Digital Video
Broadcasting-Cable (DVB-C). This proof of our system could also support the DVB-C system [22].
In a standard frequency allocation CATV transport system, when multiple even-spaced channels
are transmitted via nonlinear devices, some discrete distortion products are occurred through
various combinations of CATV carriers. In the calculation of the CSO performance, the
mathematical formula of the CSO is defined as: