Because fiber optic cables are active and feature an embedded electricity-to-light converter, they require a 5V power supply that the HDMI interface is able to transmit. Does this mean you have to worry about whether or not your source device provides enough power for the cable? Aside from this being one of the most common questions, this question is also one of the hardest ones to tackle. First off you must check the cable’s specifications for its power consumption and then check if the power output of the source device’s HDMI_5V of HDMI port is sufficient. Using AppleTV as an example, its HDMI port power output is 500mW (5V/100mA), if your fiber optic cable features a converter that requires a power supply of over 500mW, you either will not be able to use the cable at all or the use of the cable will result in subpar resolution. The current solution to this problem is to use an additional 5V power supply adapter cable similar to the one pictured below.