POE power will not interfering on Data travelling on Ethernet , Whats the logic
The data is modulated differentially onto the wire pair. Ie the current flows always anti-parallel in the pair. The transformers job is to ensure that there is no DC current (for the signal) and thus that the current is truly differential on the sender's end and that any DC component (from interference) is blocked before the data signal is passed to PHY on the receiver side. By using twisted wires, it is ensured that any interference is common mode on both wires (ie induced current flows into the same direction on both wires). Hence even large interference that would result in multiple volts at the receiver side get canceled out at the transformer and only the differential data signal is left. The PoE current is now put onto both wires of the pair in parallel, ie it flows in the same direction on both, ie looks like a large interference to the transformer. Thus it cancels out the same way.

The cancellation in the transformer works by the current flowing from the wires into the center tap. If the current is the same on both wires and has the same direction, the magnetic field they form in the transformer is the same size, but opposite sign (or direction or whatever your way of looking at it is), because they enter from different sides of the transformer winding.