[tylerjd]

The digital optical port is baked into the 3.5mm jack on most upper-end laptops and Macs. Though sadly my MacBook Air does not have one.

[mbell]

The port isn't the important bit that is added, it's the supporting circuitry and photo diode to drive it that adds complexity to the design.

[DigitalJack]

And the little physical switch in the port that broke on my last MBP. My port got stuck in optical mode.

[kennell]

Mine got stuck serveral times too. Was alway able to fix it with a toothpick.