1 Current ITU-T recommendations for optical transmission systems
1.2 Recommendation for Reach Extended PON

Passive Optical Network can however use optical amplifiers in certain cases to increase the reach, without the necessity to build up vast active-components infrastructure.

Recommendations for Reach Extended GPON with permitted amplifiers
GPON class | Optical Distribution Network range [dB] | Attenuation range from the provider to an end user[dB] | Max. physical reach (physical layer) [km]
Class B+ | 13-28 | 13-28 | 40
Class C | 15-30 | 15-30 | 40
Class C+ | 17-32 | 17-32 | 60