Problem
Windows are most often used to create connections between the indoor and the outdoors. But there are many cases when an indoor space needs a connecting window another indoor space.
Solution
Put in fully glazed fixed windows between rooms which tend to be dead because they have too little action in them or where inside rooms are unusually dark.
Related Patterns
… at various places in the building, there are walls between rooms where windows would help the rooms to be more alive by creating more views of people and by letting extra light into the darkest corners. For instance, between passages and rooms or between adjacent living rooms, or between adjacent work rooms - Building Thoroughfare (101), Entrance Room (130), The Flow Through Rooms (131), Short Passages (132), Tapestry of Light and Dark (135), Sequence of Sitting Spaces (142), Half-Open Wall (193).
Make the windows the same as any other windows, with small panes of glass - Small Panes (239). In some case it may be right to build interior windows in the doors - Solid Doors with Glass (237) …
Alexander, Christopher. A Pattern Language: Towns, Buildings, Construction. Oxford University Press, 1977, p. 897.