HDMI/DVI-D over Fiber Optics
When maximum length runs are necessary, fiber fills the
bill. There are two methods for using a
fiber in an HDMI/DVI environment. For
runs up to 300-feet there are multi-mode fiber cables that incorporate
fiber-optic converters in each connector which convert HDMI signals into light
pulses, and then back again at the display.
These cables use a plastic-clad glass fiber, which offers a high degree
of ruggedness and flexibility. A
multi-mode fiber solution is available in Plenum-rated CMP and in CL2 versions
for residential installations. Using
fiber you will have no problems meeting electrical codes. Further, the very nature of a fiber connection
eliminates any possibility of a ground loop, RFI or EMI. After all, the signal is light and it can’t
be affected by magnetic interference or noisy light switches! Fiber is a powerful solution.
In digital signage there is sometimes a need for distances beyond 350-feet with DVI-D and HDMI signals. In such applications a single-mode fiber solution can be used. Single-mode fiber can deliver a 1080p signal up to 1500 feet without loss!
There is a cost to using fiber – maybe there are a few costs. First is the price… A 10 meter solution would not cost the $150.00 of a copper-based interconnect as detailed above. And it won’t cost the $562.00 of the dual Cat5e solution. A typical fiber solution would have a price tag closer to $850 for a 10 meter run! Of course the price per foot comes down as the length goes up. If copper costs $4 per foot (at its maximum run of 75 feet), and dual Cat5e costs about $4 per foot at its maximum of 150 feet, fiber tips the scales at only $5 per foot for a 350 foot run. If you use the technology at its maximum limitation, the prices are equitable. With the typical runs encountered in home theater or presentation/conference room installations the difference in price becomes significant indeed. Often this price differential doesn’t reflect a performance difference.
Another cost of using a fiber solution is in the HDCP “handshake”. Bluntly put, fiber optic doesn’t shake hands! Typically a separate Cat5e must be run to ensure compliance with HDCP protocols. Of course the minute you add copper to a fiber-based system you re-introduce the possibility of a ground loop problem.
