Schemes for generating W state of paths and W state of polarization   photons
  In this paper, we give two very simple schemes to produce two kinds of W states, one kind is path W state with one photon and the other is multiphoton photon polarization W state. These schemes just need a common commercial multiport fiber coupler and single photon sources, they are feasible by current technologies. 
Bao-Sen Shi and Akihisa Tomita