HDMI Fiber Optics & Copper Cable Considerations

When it comes to HDMI / DVI connectivity, you have two choices: Copper or Fiber Optics. Which is right for you?

As digital displays become more popular, and more people understand that a DVI or HDMI "pure digital" connection delivers the best HD picture quality available today, the decision of which type of cable to use is challenging and requires thoughtful consideration.

Today's video installations grow ever more complex, with source components positioned a good distance away from the display. The distance is the biggest factor in determining which technology to use.

There are two choices when it comes to choosing the technology for your connection cable. Copper or Fiber Optic. This subject has been debated since the introduction of optical and coax digital audio connections and it is believed that both are comparable, that choosing one over the other does not affect the audio quality. This is true for low bandwidth audio especially when the distance is short.

However, full motion uncompressed digital video signal is a different story. Due to the nature of digital signals and the natural impedance and inductance of copper, fiber optic conversion technology is usually the best connection medium for longer length DVI and HDMI signal extensions. Fortunately, with digital video, both technologies use the same connector type. The DVI/HDMI digital signal is both high-speed and high-bandwidth. Typically, 1080p signal would mean 1920x1080 pixels refreshing 60 times per second. At this high rate of speed and large bandwidth of data, the impedance of many copper cables can cause signal loss at about 15 feet - which results in digital artifacts (sparkles), pixilation (tiling) and/or no picture (blue screen).

A well built, high quality copper cable with low impedance in shorter lengths will do fine at 1080p and is used in conjunction with many fiber optic extension products. There are also some copper cables at longer lengths (50ft and beyond) that are known to pass 1080p video without pixilation or degradation. However, to accurately compare between fiber optic cables and copper cables, the two should be compared with same testing environment and set-up. Copper cables and booster technologies are somewhat dependent on the 'strength' of the transmitted signals. Computer video cards transmit the cleanest and strongest signals and many A/V components such as DVD players and Cable/Satellite receivers transmit weaker signals that may affect the end result.

In addition, the lifetime of these cables should also be considered. The optical conversion ICs are guaranteed to last at least 80,000 hrs of continuous operation. Fiber optic cables are also immune to lightning and other electrical interference such as RFI.

With Fiber Optic Conversion technology, there is theoretically zero impedance and thus zero loss as the digital electrical signal is converted into light-waves at the video source and the signal travels in light form till it reaches the display and is reconverted into digital electrical signals. Be sure to note the difference between "boosters" and true optical conversion technology if you want to make sure all the pixels reach your display. "Boosters" used over copper wire amplify the electrical signal to make it "stronger" to minimize signal loss. However, the biggest problem with this technique is that when the signal is amplified, bad data may also get amplified at the same time, which can result in amplified digital noise and/or pixel loss. Another problem with many "booster" solutions is that the DVI & HDMI signals can only travel up to about 60ft before the signal needs to be re-boosted. This is not only inefficient; it can be very costly. Last but not least, boosters are electrical devices that are not UL approved for in-wall locations. Custom installations that require in-wall capability over long distances require Fiber Optics because it converts the electrical signal into light-waves and thus maintains the integrity of the signal data up to 395 ft without interference by peripheral devices.

This is the very reason why IT infrastructures and cable TV companies are upgrading their networks to fiber optic. Considering the fact that the bandwidth of IT communication (generally less than 0.6Gbps) is much lower than uncompressed video data (1.65Gbps), it is easy to understand why fiber optic is better when it comes to high bandwidth digital signal transfer for long cable runs.

Recently introduced regeneration technology looks promising, however it needs more testing. These devices coupled with high quality low impedance copper cable may successfully extend the distance beyond 30ft. However, with fast moving "full motion" gigabit HD video at higher resolution (1080p and above), this will be the true test between copper and fiber optic technology.

Connectivity products such as cables are one investment you will need to live with for at least 10 years. Consider it an investment as cable quality does make a difference and it will stay with your system for a very long time. Your current AV system may only do 720p or 1080i at this time and copper cables may be fine. However, as digital video technology is changing rapidly, you may be upgrading your DVD player or TV in the near future and you want to make sure your cables will work with your new system (especially, if you are burying the cables in the wall). Buy a cable that is guaranteed to work at 1080p regardless of whether it is a proven copper solution or fiber optic alternative. Fiber Optics may be more expensive, but the price differential may be worth consideration for future-proofing your system now.

It is always important to test your cable before your installation. Make sure to check the return policy with the merchant before making a purchase. You don't want to run the cable under the floor or inside the wall and find out the cable is not working out for your system. Test your new cable for at least a few hours to ensure it works on all of your system' supported formats.

Many thanks to Minsoo Park of PureLink for contributing this article.

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