Apple could be testing a technology called Li-Fi, a play-on-words of Wi-Fi, according to code found within iOS 9.1.
The technology is about 100 times as fast as Wi-Fi--with speeds of about 224 gigabits per second--because it uses the light spectrum to transmit data.
It's unclear how Apple might use the technology or whether it will make it into the rumoured iPhone 7.
No technology available on the market uses Li-Fi, so there is little to compare it to. One use could be talking to other devices within the same room, such as the Apple TV. The high data speeds mean a film could be sent from an iPhone to the TV within seconds, ready to stream. (This is just speculation, though--it's still early days for the technology.)
Apple filed for a patent in 2013 that talked about an "optical modulation using an image sensor" that used the iPhone's camera to transmit data via light, a technology that could be used with Li-Fi.