Mora datas:

The wires are in copper or in a similar alliage. It can be one or two wires.

The wire is contained in the tubes and at the bottom of the torpedo but there's no real traction from the torpedo, the wire is floating.

Depending the model, the wires contained in the torpedoes are between 10 and 30 km longes and are in the tubes 10 to 20km long.

The most recent torps, like the Blackshark or the DM2A4 are using optical fiber, thinner but also allowing more informations to be transmitted, such wire can be potentially 40km long.

Source:
Fil de guidage des torpilles

More about the DM2A4 here:
Key Publishing Ltd Aviation Forums - Torpedoes


Bon Vent, Bonne Chasse,
Jan