As with every aspect of live production there are a myriad of choices to make and cable selection is no different. To start things off I'd like to list off a number of common signal types dealt with, from there I'll take us into what kind of cabling is used for each type and why.
SDI (Serial Digital Interface)
HDSDI (High Definition Serial Digital Interface)
Composite Video
HDMI
Single Mode Fiber
Multi Mode Fiber
Analog Audio
AES
Ethernet
RS232
RS422
Sync (Black Burst)
Triax
2-wire Comm
4-wire Comm
DC power
AC power
We'll group together a few signals by the cable type they use which is coax. Coax is one of the most commonly found cables in live production environments. SDI, HDSDI, composite video, AES, and Sync all utilize a coax cable with a a BNC connector
Each signal type differs but lets first focus on SDI. SDI stands for serial digital interface, which basically means the signal over the cable is a digital square wave instead of a nice curvy sine wave. I'll also quickly note that since HD video has become the new standard, the term SDI is now used in the video world to refer to "HDSDI" signals. Techs, engineers and video ops just dont have the to add the additional syllables. The benefits of SDI are massive and allow us to send video from device to device without "loss". Older analog video (like those yellow RCA connectors you may remember) uses an analog sine wave and will take little hits and simply lose quality by sending it either to multiple processor devices or over long distances. This loss appears as the fuzz, static, and weird washed and blown out colors common in VHS era video. SDI, however, eliminates all these issues! There is only one rule to obey with SDI: don't go over the cliff. This is a term any engineer worth their salt will be familiar with and it refers to the sudden drop of the video signal when we attempt to send it down a cable much longer than 300ft.
I'll leave the more in depth explanation of this for another post where we can dive into all the intricacies of SDI, its different flavors, bandwidths, how cable type and diameter effects the signal, and what that signal even looks like when we scope it. The simple point is: we can't send video more than 300ft on copper cables in SDI format. For that there are two solutions: we can place a DA in line. This is a Distribution Amplifier, which in this case is being used to reclock the SDI signal (the fancy term for signal boost). The other option is to convert our video signal to fiber!
This brings us to single mode and multi mode fiber: Each of these has an entire post to be made which I'll link here, But lets just keep it simple and remember multimode is for short distance high bandwidth signals and almost exclusively seen in data centers, where as single mode is for long distance. Most of what you'll see in live production is single mode. Specifically single mode Tac fiber. This is the Tactical sheathing around the fiber wire.
The thing about fiber is that it is actually glass. There is no copper in these wires. The digital video signal from SDI is converted into light pulses that is sent down the fiber cable with a laser. Over fiber we can send video signals over distances of 20 miles or more with absolutely no delay whatsoever. The tactical sheathing solves fiber's biggest problem of being fragile, leaving only one other downside: cost. This is just one of many reasons the cost of live production can be so high, some events require cameras and signal flow to cover thousands of feet at events and logistically fiber is the most cost effective way to make this happen.
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