这个是在ITU G.984.2-200803 Amd2 有定义的，CLASS B+比CLASS C+灵敏度低 4dB.
Table V.1/G.984.2 – Optical power levels for the 2.488 Gbit/s downstream,
1.244 Gbit/s upstream single-sided reach extended system (Class C+)
Item Unit Single fibre
Reach-extended OLT: OLT
Mean launched power MIN dBm +3
Mean launched power MAX dBm 7
Downstream optical penalty dB 1
Bit error ratio (pre-FEC) [Note 1] 10–4
Minimum sensitivity [Note 1] dBm –32
Minimum overload dBm –12
Upstream wavelength range (G.984.5) nm 1290-1330
ONU: – ONU
Mean launched power MIN dBm +0.5
Mean launched power MAX dBm 5
Upstream optical penalty dB 0.5
Upstream wavelength range (G.984.5) nm 1290-1330
Bit error ratio (pre-FEC) [Note 2] – 10–4
Minimum sensitivity [Note 2] dBm –30
Minimum overload [Note 3] dBm –8
NOTE 1 – The OLT sensitivity assumes the use of the optional RS (255,239) FEC capability of the G PON TC layer, as well as intrinsic detector technology improvements, e.g., SOA preamplification.
NOTE 2 – The ONU sensitivity assumes the use of the optional RS (255,239) FEC capability of the G PON TC layer with the current class B+ ONU detector technology.
NOTE 3 – The ONU overload is set at –8 dBm to be common with the class B+ value, even though in this application –10 dBm is sufficient.
