The Data Rate Explosion

The displays of mobile and consumer electronics devices have undergone a remarkable transformation in just a few years. We have gone from SD (480i) resolution to HD (1080p) then 4K and 8K and the resolution of each RGB pixel has also increased from 8 bits to 12 bits. The number of pixels which need to be transported has increased almost 300 times. An 8K display operating at 60 Hz and 12-bit colour needs a bandwidth of around 72 Gbps in order to transport all the pixels.

8K TVs, monitors, and gaming consoles are already available. PC gamers drive 4K monitors at up to 144Hz. 4K smartphones are on the market. In addition, VR / AR (virtual / augmented reality) products which require 4K at 120Hz displays are becoming mainstream.

It is not only displays which now have high resolutions. Cameras in mobile and consumer devices are already capable of shooting 4K video.

This has led to the development of several high-speed consumer standards such as DisplayPort 2.x (up to 80 Gbps), HDMI 2.x (up to 48 Gbps), and USB 4.x (up to 120 Gbps). However, conventional copper cables intended for these standards are thick, bulky, heavy, and limited in length to 1m or so depending on the data rate. Copper has shown its limitations.

The same data rate explosion has also occurred in other markets such as medical endoscopes, drones, video conferencing, and security cameras where high-speed connections using standards such as MIPI D-PHY are needed between the application processor and the displays/cameras. In addition, these devices have very stringent requirements for low power consumption, extremely small form factors, and reduced EMI (electromagnetic interference). Optical connections are ideal for these applications.