Er, I see there is a little confusion.
When talking about the E-side and the D-side, we are just referring to the copper (or aluminium) cabling to the exchange or to the customers premise from the PCP.
In your case, a FTTC user, there is just 50V DC with the analogue voice signal superimposed upon it that traverses the E-side cable. On the D-side cable, from the PCP to your SSFP, there are three components -- 50V DC, the analogue voice signal and the VDSL2 signal (at radio frequencies).
The VDSL2 power level between the FTTC DSLAM and the active CPE (the
Huawei HG612), through the D-side copper (or aluminium) link, has already been mentioned.
You are correct that there is another pair (Tx / Rx) of power levels to be considered. However this is not through the E-side cable but is through the fibre optic feed to/from the FTTC DSLAM from/to its source -- which may not necessarily be the same exchange building to which the E-side cables are connected!
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