What does PON-T or PONT refer to?

PON-T refers to a Passive Optical Network device that terminates the fiber connection (opposed to pass-through or monitoring devices)

The PON-T refers to a PON Terminating device or instrument that is used at the end of the fiber link (or segment) under test (opposed to pass-through or monitoring devices). For example, a PON-T Optical Power Meter is a selective or filtered OPM that is to be connected at the end of the fiber under test.