How should I install a signal cable duct from new home office to a wiring closet?
For the duct work, since we don't know how many cables you are talking about, I suggest ENT (Electrical Non-Metallic Tubing).  It is flexible, corrugated and comes in a range of sizes, same as PVC.  You can even use PVC connectors on ENT if in a bind.



For termination, you can either use a box / terminating structured media center or make your own with a J-Box, but I suggest the SMC's.  The SMC's come in different sizes, depending on the manufacturer, and different modules and a surge suppression power system made for the box.



The SMC's are for RG6, or quad, Telephone, Cat5 and or Cat6, speakers, IR, securitry and the list keeps getting bigger.  This is a link for Leviton, and there are many more manufacturers of these.

Remember, no tight turns or hard pulling, these cables are not made to be tugged at real hard at, like stretching the twists inside cat5 cable.  If you can make the bend in ENT your wire radius will be OK.