The DS1102 can be powered through its power jack or the optional Power over Ethernet (PoE) module (letter " P" in the model numbering scheme).
The PoE module should be powered by 48V (nominal), which is standard for PoE equipment. Your PoE-enabled hub will take care of this. The PoE module outputs 12VDC.
Internally, both power sources are connected to the DS1102's power regulator through two diodes, as shown in the diagram below.
Note that DS110x devices cannot accommodate the PoE and Wi-Fi options at the same time.