I'm not sure you would want to do that..from my experience the Tello gets very hard to control if the light is not good..the sensors on the bottom do not appear to work well in low light. Let me know if you have any luck in finding a solution.
Tello uses a downfacing camera for the VPS. I think IR sensor is only to help improve altitude hold when flying low. In higher altitude it seems to rely on barometer and VPS only.
VPS does OK in low natural light but even bright artificial light indoors isn't really good.
For night flights you'll have to do without VPS support, that is no position hold, bad altitude hold performance, no Return to home. It will be like the other toy drones, and needs more flying skills.
You are already spoiled by Tello's pilot assist features (I think Tello flies more like a large GPS drone than a toy). Altitude hold and position hold are way better than any other toy drone I have had. If Tello is your first drone I'd practice unassisted flights with a cheap 15 Euro drone first.
I added a light designed for a mountain bike handlebar to the Tello this evening for fun, and it works out really well.
As previously mentioned, no VPS at night, you need to be able to fly in ATTI mode before going out at night and flying the Tello. To practice this put your guards on and place some electrical tape over the two IR LED's and the camera in the middle and with that said, another caution you can land the AC as it doesn't know the height and if you flip it, it will not turn off. Enjoy!!
I thought Tello performed poorly at night also, as I experienced twitching, latency, lack of control, and random landing sequences when attempting to fly in low or no light. Thing was, I didn't get the best performance during the day either. Ultimately, I narrowed it down, and fixed all issues by rebooting my Galaxy S9+ every time before flying. This results in a Tello that is responsive, and very stable, regardless of lighting. While position may drift in low/no light, altitude holds beautifully.
As well, you'll find a night flying session that I recorded last night. Super fun. The couple minor twitches you may see in the video were likely due to interference from my Mavic Air, which I used to record the video as it sat stationary on the top of my truck. Little to no glitches in control when night flying otherwise. Note, I rarely fly without a repeater. The video happens to be without, as the repeater had somehow reset itself, and was not configured when I set out to record.
Good luck. Let me know if I can answer any questions. Many of my most enjoyable flights are night flights. Assuming you have a repeater setup, you may discover you can fly further out (LOS) at night, than you can during the day.
Which is no surprise: the position is held by the visual positioning system which (as the name implies) needs vision to work correctly; the altitude is kept by the onboard barometer which doesn't need any light at all.
Something must have happened to that thread: it does not exist. And right now your message counter is on 1 which indicates that no other post of you than the one I am replying to exists in this forum - for whatever reason.
But fiber optic sounds interesting....
Edit: the linked thread fortunately resurfaced from the depths of forum moderation
Reminder to all (just sayin'): In some countries outdoor night flights with UAVs are strictly forbidden so always make yourself familiar with the local regulations before taking off (and make an informed takeoff decision).