The order is for 122km of medium voltage submarine cable for the project, which is located in the Irish Sea. Installation is scheduled for Q3 2013.
West of Duddon Sands was signed off in June 2011 by Dong and Iberdrola subsidiary ScottishPower Renewables. The two companies agreed a 50/50 joint venture to build the project.
The £1.6 billion project will consist of 108 Siemens 3.6MW turbines and will be among the largest offshore wind farms in the world at the time of commissioning in 2014.
ScottishPower Renewables chief executive Keith Anderson said: "West of Duddon Sands will be the first offshore wind project in our pipeline to be commissioned, and marks the start of our extensive investment programme in the offshore wind sector.