What is optical audio?

As anyone who has lived with a bad landline connection or a weak signal from the cable box can tell you, signal degradation can really ruin your day.

Copper, which still provides the core of most wiring, can suffer significant signal degradation over distance. Coaxial cable -- used to transmit television, telephone and computer network signals -- comes packed with shielding to prevent signal bleed-off, but losses due to electrical resistance still weaken the signal over distance. Shielded audio cables include some protection from outside noise, but suffer the same resistance issues [source: National Instruments].

Luckily, we have fiber optics.

Fiber-optic cables offer the kind of low signal loss and high data rates that telephone and Internet users demand by transmitting information as light through thin plastic or glass wires. These cables have total internal reflectance, meaning that light bounces along inside them without escaping. Glass fibers can transmit such "lossless" signals over great distances without needing a power boost [sources: Encyclopaedia Britannica; Wood].

By the same token, optical audio delivers higher-quality sound than older copper-wire connectors by converting electrical signals to light and piping them through optical fiber.

The age of optical audio dawned in the 1980s, when Toshiba created Toslink, the first optical audio cable. The Japanese electronics company had developed its own compact disc player and was looking for a way to output the improved digital audio quality to speakers and headphones. Appropriately, Toshiba chose an optical solution for CDs, an optical storage medium [sources: Modern Home Theater; Toshiba].

In an optical audio setup, the digital electrical signal from the source -- say, a DVD player -- is converted into light by a device called a transmission module. In Toslink, this module consists of an LED, or light-emitting diode, and a drive circuit, usually sent through plastic fiber, whereas ST Fiber Optic uses glass fiber and a red laser light at a 680-nanometer-wavelength [sources: Modern Home Theater; Toshiba]. The signal then speeds along the optical cable to the destination device, usually a television or audio receiver, where a light reception module converts it back into a digital electrical signal. From there, the device transmits it to your speakers or headphones.

Because it sends only sound, an optical audio cable is usually used with a video-only cable, such as DVI (Digital Visual Interface) or S-video.

So, what's the catch? Well, optical cables tend to be somewhat brittle, and the plastic ones are not as lossless as their glass counterparts. The reconversion of light into an electrical signal has been known to introduce errors. More to the point, however, some argue that HDMI (see sidebar) has rendered the format moot [source: Johnson].

Who is right? As with most arguments among audiophiles, the truth is in the ear of the listener.

After years of feeling lost in the formats, I tackled this article with a combination of excitement and trepidation.

On the one hand, I hoped that, at long last, I might decode the alphabet soup, untangle the mass of cables and reel in the rhetoric to discover just what all those jacks were for. On the other hand, my previous forays into the field hinted that my hopes for clarity might end up squelched.

It's not that I'm a technophobe -- quite the opposite. I can upgrade my own computer (although, admittedly, that used to be a lot easier) and, in college, I helped my mom program her VCR so many times that I could talk her through it blindly over the phone, like a tower jockey walking a non-pilot through landing a 747.

It's just that, somewhere along the line, a few cables became many, the color codes ceased to mean what I thought they meant and the number of prongs stopped corresponding to the number of jacks.

More than that, though, it was that no one could give me a straight answer as to which solution was the best. There's a reason for that, and it's the chief stumbling block to writing an article about consumer electronics: The world of audio is steeped more in lore than in hard facts; there's as much snake oil in those wires as sound.

I did my best to steer clear of the hype and to stick to the facts. As far as they go, they say that the choice depends on your equipment and how you intend to use it -- oh, and whether you've already lost so much high and low range to loud music and age that fancy cables no longer matter.

Contentious, normative questions like "best" and "worst" are best left to the audiophile, if for no other reason than there is simply no clear-cut answer. Don't believe me? Try walking into a guitar shop and asking for the best amp.

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