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Frequently Asked Questions

Why & where are fiber optics used?
Fiber optic transmission systems are used wherever immunity to electrical noise (both electromagnetic and RF) is desired. They are also used where isolation between both ends of a system is desired (such as in video transmission) to avoid ground loops, for high voltage isolation since fibers do not conduct electricity, and in applications where wide band signals or data rates need to be transmitted over long distances.
 

Using existing fiber in my facility and cannot get my multimode 850 or 1300 nm transmission system to work. What's wrong?
Be certain that the fiber optic cable is indeed multimode fiber. You will have to look at the fiber cable jacket to determine this or contact the installer if it is not clear. Single-mode fiber can look the same as multimode and even the connectors can look the same (especially if they are STs) but the operation is completely different. The light carrying core of single-mode fiber is only 8 to 10 microns in diameter while multimode fiber has a core diameter of 62.5 microns. This means that a multimode transmitter cannot possibly "launch" enough light power into a single-mode fiber. If the fiber turns out to be single-mode, you have no choice but to switch the transmitter and receiver.

Using existing fiber in my facility and cannot get my single-mode equipment to work properly. what's wrong?
Be certain that the fiber optic cable is indeed single-mode fiber. You will have to look at the fiber cable jacket to determine this or contact the installer if it is not clear. Single-mode fiber can look the same as multimode and even the connectors can look the same (especially if they are STs) but the operation is completely different. The light carrying core of single-mode fiber is only 8 to 10 microns in diameter while multimode fiber has a core diameter of 62.5 microns. This means that a single-mode transmitter will "launch" too much light power into a multimode fiber with the result that the received signal will be distorted or not recovered at all due to overloading. If the fiber turns out to be multimode, you will have to use an optical attenuator somewhere along the fiber optic cable path between the transmitter output and the receiver input.

If fiber optic equipment is immune from electrical problems, how come an electrical storm can disable a transmission system?
The fiber optic cable is truly immune and will not transmit electrical spikes back to the equipment as it normally contains no metallic elements and only conveys modulated light. However, Fiber optic transmitters and receivers are electrical devices and their internal circuitry and power sources may not be immune to power transients, high electromagnetic fields and loss of operating power.


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