Let us analyze each statement:
* Option A :
* Correct : WDM1r multiplexers can be flexibly deployed close to the Central Office (CO) or closer to the user, depending on network design requirements.
* Option B :
* Incorrect : While GPON and XGS-PON share the same ODN architecture, simply changing the optical modules on an ONU is insufficient to support XGS-PON. The ONU hardware and software must also be compatible with XGS-PON standards.
* Option C :
* Incorrect : The deployment of WDM1r multiplexers introduces additional optical loss, which must be accounted for in the calculation of optical link attenuation.
* Option D :
* Correct : GPON (1490 nm downstream, 1310 nm upstream) and XGS-PON (1577 nm downstream, 1270 nm upstream) use non-overlapping wavelengths, allowing them to coexist on the same ODN using WDM.
Thus, the incorrect statements are B and C .
References:
* HCIA Huawei ACCESS Official Documentation , Chapter: GPON and XGS-PON Coexistence.
* ITU-T G.9807.1 Standards for XGS-PON .