How do I have to use Devexpress XPO in PRISM modular application?

I'm working on a开发者_如何学运维 project with 20+ Modules with the following Technics:

WPF 4.0 , PRISM 4 , Unity 2.0 , MVVM Light , and Devexpress XPO as and ORM

I have no idea how to plane to use a XPO Session in my modules?

I have faced the following items but don't know witch is the best?

1. Using a global static Session property
2. Use a global static connection string
3. Use a global static IDataLayer
4. use and Registered Interface in PRISM
5. or maybe you can give me a idea?