Down to the Wire
Signal transmission methodology is an essential ingredient to optimize a video surveillance system. While more than half of existing systems use coaxial, Ethernet cabling is growing fast as IP-based systems proliferate. And then there’s fiber optics. Learn how to evaluate and balance critical factors to achieve the best results.
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Why UTP Is Giving Way to Ethernet
UTP is often chosen over coax or fiber because of its ease of installation, cabling options, noise immunity and ground loop isolation. UTP cabling is lighter and easier to install than RG-59U and the material itself is less expensive than comparable lengths of RG-59U. Unlike coax, UTP employs a robust balanced mode of transmission, making it highly immune to interference. Video signals can reside in the same wire bundle with ringing telephones, Ethernet, 24VAC, RS-422, RS-485 and other video signals (providing they are not traveling in both directions down the same cable). They can also reside in high-noise environments such as elevator traveling cables or near fluorescent lights, radio transmitters or motors.
If EIP networks utilize UTP cabling, the question must be asked, “How can UTP be giving way to EIP?” The answer: It’s not the wire; it’s the infrastructure around the wire.
In an EIP system, the UTP carries a whole series of communication protocols such as IP, TCP (transport control protocol) and various Microsoft protocols like NetBEUI. EIP uses all the transport and control protocols found in traditional Ethernet systems including TCP, IP, and the media access and signaling technologies found in off-the-shelf Ethernet interface cards.
Thus, EIP works transparently with all standard off-the-shelf Ethernet devices found in today’s marketplace. It also means that EIP is easily supported on standard PCs and all their derivatives. Basing EIP on a standard technology platform ensures it will move forward as the base technologies evolve in the future. And, since it is installed in so many facilities already, there is no need to install additional UTP cable or special multiplexers/de-multiplexers. That would be redundant.
Compared to fiber, UTP transmission is significantly less costly, from cable and installation costs to tooling and transceivers. Nonetheless, fiber is still the answer for long runs (i.e. more than 1,500 feet).
In addition, there still remain challenges and costs when pu
shing analog video signals through UTP cable. It requires conversion of the camera’s unbalanced BNC output into a balanced signal that can be carried on one pair of the UTP. When reaching a head-end or recorder, the signal must be reconverted to handle a standard BNC-type connector. That means use of a balun, which allows a signal of one impedance value (a measure of opposition to alternating current) to be transmitted over a cable that uses a different impedance value.
There also remains a serious distance limitation with UTP cabling infrastructure that hinders placement of cameras. For example, if a camera is located 1,000 feet from the head-end, without any active signal conditioning at some cost, about 37% of the information will be lost in transmission. That does not count the need and cost for signal amplification, ground fault correction and surge protection.
Cost Aside, Fiber Full of Advantages
Fiber-optic technology, a method of sending and receiving information over great distances using light as the carrier, boasts significant advantages, whether as a backbone or a total transmission solution. Among fiber optics advantages:
- Better quality transmission
- No interference (lightning strikes, short circuits, “cross talk,” EMI, RFI, high voltages in fluorescent lights, card access door strikes, outdoor lighting systems)
- Lightweight
- Stable within a wide temperature range
- Long service life
- More secure (not easily tapped into or interfered with)
- Extremely high bandwidth
- Tech growth (ongoing developments increase the amount of data transmitted)
The bandwidth capacity of a single strand of standard multimode fiber is more than 45 times that of a Cat-5 cable, while the maximum bandwidth capacity of single-mode fiber has yet to be reached, according to fiber optics experts. Attenuation in fiber optics, also known as transmission loss, is far less than the equivalent loss in copper or UTP cables. There is no doubt that fiber optics can handle massive amounts of digital information across vast distances, securely and with immunity to interference.
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