Benefits of Using Fiber Optics

The use of coax is the most limiting part of any video or data transmission system. In terms of video, 1000 feet is the quality limit of standard RG-59 when transmitting a black and white picture. In truth the picture starts to degrade at the point where the signal enters the cable. High frequencies are attenuated more than lower frequencies and results in the loss of picture resolution. Therefore, distance is a very important benefit of fiber systems. It is possible to transmit a video signal 2 to 3 miles with a simple video transmittion system and there is virtually no signal degredation. American Fibertek can offer a system to transmit a video signal up to 40 miles with no repeaters or loss of signal clarity.

Fiber cable has high bandwidth capacity. Once a backbone is installed, there is a tremendous increase in the potential to move information. American Fibertek provides equipment that takes advantage of this capacity.

Our bi-directional products allow multiple functions to be transmitted similtaneously in both directions on a single fiber. Our low cost video multiplexers allow four channels of real time video to be transmitted on a single fiber.We can provide electronic fiber optic solutions for complex system needs.

Other Benefits:

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Balanced Audio

Input Connection

To connect an unbalanced signal to the input, the audio signal is connected to the plus input. The shield or ground wire is connected to both the minus and the ground terminals. In either input configuration, the input impedance is 600 Ohms.

Output Connection

The balanced connection is made across both the plus and the minus terminals. The balanced output impedance is 600 Ohms.

To connect unbalanced, the plus output is used for the audio connection, along with the ground terminal. The signal level will be half of the input (-6dB) in this configuration. The unbalanced output impedance is 300 Ohms.

Signal Level

Higher input levels will cause increased distortion. Up to +3dBm, the distortion will increase a small amount. Above this level the distortion will increase rapidly. Lower input signal levels will reduce the signal to noise ratio.

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Loss Buget Calculation Spreadsheets

Loss Budget Calculations in Kilometers

Loss Budget Calculations in Miles

For information regarding the concepts of loss budget, there is a complete explanation in our History of Fiber Optics.

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EIA422 and EIA485 Data Signals

RS422

Because there is only one transmitting device on the network, this one may remain active at all times. There is no need for the driver to go into a high impedance state to allow others to "talk." This configuration using multiple drivers on the same wire pair is exclusive to RS485 described below.

EIA485

Data wiring can use two wires or four wires. Using two wires, the system works in half duplex. This means that data is exchanged between to points sequentially. When a four wire system is used, the system may be full duplex. In many cases the system head end controller will continuously poll data to all remote devices on a transmit pair. The remote devices all respond (one at a time!) back to the head end. This property of the network rests solely in the hands of the software (firmware).

NOTES ON HiZ

The best place to locate such as resistor is at the furthest electrical input device on the wire pair. For instance if several RS485 inputs are connected to one driver at a head end, the wire connection would loop across all inputs in a chain. The last input in the chain would need to be terminated. Typically any value of resistor from 100 to 220 Ohms 1/4 Watt is sufficient to stabilize the signal line.

Multimode vs Singlemode Fiber

Based on the names given these fibers, first impressions would be that multimode fiber would be more efficient than singlemode fiber. However, the reverse is generally true.

The term multimode comes from the fact that light can travel in more than one path through the core of this fiber. The relatively large core allows light to travel both straight down the center or to bounce from side to side in a zigzag pattern. Light traveling from side to side takes longer going down the fiber than light traveling straight so the signal at the end of the fiber is dispersed. This dispersion effect does not become significant until the signal has traveled long distances such as a mile or more, or when data bits are packed close to each other.

The relatively small core found in singlemode fiber only allows one path of light directly down the center of the core. This keeps the signal intact for distances in excess of tens of miles.

Since singlemode fiber is half the cost of multimode fiber and it has more efficient signal transmission, the obvious question is why use multimode? The answer is that the overall cost of an application is generally less expensive when done in multimode. This is because the transmitters and receivers required to convert electronic signals to fiber optic signals are four times more expensive in singlemode than in multimode.

Camera and control systems used in most security and surveillance designs typically use multimode optics. The low speed data used in these systems allows for distances to three miles with the lower cost optics. Intercom and contact closure used for gates and alarms can also be transmitted up to three miles on multimode fiber. For long distance projects such as traffic management and distance learning, the extended range of singlemode optics is the transmission of choice.

Therefore, when designing a high data throughput or long distance application, a singlemode system is preferred. When designing an application which has a distance less than two miles with moderate data throughput, multimode is more economical.