Triggering a PIR detector

I have a PIR detector in my office that controls the light. Sometimes it doesn't detect me, so I consider building a device to constantly trigger it.

Do you have any idea on how to activly trigger a PIR detector? It is my understanding that they are tuned for 7-14 micrometer wavelength, but few if any diodes are in this range, so one would probably have to create the light in another way.

Any suggestions are greatly appreciated.

7-14 μm is far IR rather than visible light, fully absorbed e.g. by glass windows, but passed by polyethylene films. Any pulsed heater can be used as a far IR source.

Most PIR sensors have an adjusting trimmer to set the sensitivity. PIR sensors also are ONLY sensitive to a target movement ACROSS the field of vision. This is why they utilize a plastic Fresnel lens which "modulates" incoming IR radiation from a target (you or another person).
If your PIR sensor fails to detect you, you can readjust its sensitivity a well as its location so that it triggers when you or another person CROSSES its axis of the vision field.
Your cloth might block your own radiation. You can wave your hand before the sensor, or, use an IR LED or a red laser pointer to trigger it.

It might be more convenient to use a optical fiber detector to instead of PIR detector. An optical fiber detector can make very long distance fiber test.