The AMT Explorer barge was transporting the cables for the Deutsche Bucht and Butendiek wind farms from near Naples in southern Italy to Bermenhaven in northern Germany when it spilled its cargo.
No crew were injured in the incident, Pysmian said in a statement.
The firm said that the cables are valued at around EUR 28 million, but that it has "adequate insurance coverage" to compensate for the loss.
"Prysmian and Tennet are working at their best capabilities to avoid consequences that may affect the project execution timetable," Prysmian said in a stamtement.
The barge is owned by Augustea Anchor Marine Transportation, while Smit Salvage is handling the wreck following the capsizing.
The event took place in international waters, 93 kilometres south-west of Sardinia.