According to documentation there are 2 possibilities for powering 1608 IP phone. One is using PoE Ethernet switch and another is using local power adapter.
But in case when there is an existing non-PoE Ethernet switch it could be useful to add just PoE injector. Avaya 1151D1 power injector is only for 9600 IP phones and in documentation is stated that 1151D1 shouldn't be used for 1600 phones.
I suppose that any standard PoE injector should be working with 1608 IP phone?
regards,