Customer reported that ONT HG8247H5 is working smoothly but only CATV light is not working.
1, First, to avoid CATV signal through splitter has some problem, it is suggested to plug CATV generator signal directly into ONT and then to check whether CATV light will turn on; if not, it is confirmed that CATV signal is not correct. But the test shows CATV generator signal is correct.
2, Secondly, we check and find one more problem ONT LOS light on HG8247H5 is in RED. We guess if PON port output optical power range around 2~5dbm is too large, thus at lease 15 ~20dbm optical attenuator needs to be added on GPON ports, since the PON port sensitive on ONT is below -10~-20dbm. If PON port output optical power is too large, ONT may not receive the PON signal, thus also can not receive CATV signal. But even after we add enough optical attenuation, the CATV light is still not working.
Optical attenuator, is a passive device used to reduce the power level of an optical signal. Owing to that too much light can make a fiber optic receiver saturated, the light power must be reduced by using fiber optic attenuator to achieve the best fiber optic system performance.
3, Thirdly, We know the receiver sensitivity of CATV on HG8247H5 is -8 ~ +2dbm, we try to adjust CATV signal in very low power within ONT CATV receiver sensitivity range, then also plug CATV signal directly into ONT, finally HG8247H5 CATV light starts blinking normally.
If we check CATV signal on high power, CATV light on HG8247H5 will not be blinking; If you adjust CATV signal within ONT CATV receiver sensitivity range -8 ~ +2dbm, ONT can receive the CATV signal, and then CATV light will be blinking normally.
To adjust CATV signal in low power within ONT CATV receiver sensitivity range.