For WDM product, we need to use attenuation on many places and we have some recommended places for it. It is not needed to follow strictly, but if we follow the recommendation, we will find it easy for us to find the cause of trouble or any other related problem.
Recommended place for attenuation as below:
1. Don't put the attenuators into OUT / Tx ports. It is not strict and not because of reflections or some other reason.
2. Place fixed attenuators on IN/Rx ports. It is not strict too.
3,Dont place any attenuators in RAMAN IN port. It is strict.
4,Tunable attenuators only Recommended for the IN port of OAU/OBU. Of course we can place tunable attenuators anywhere, but it's according to cost, we can use other fixed attenuators to replace it.
