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System Loss Budget Example
To calculate a system loss budget let’s use the following example:
The ten video cameras in Building A are being transmitted to Building B’s control room. Building B is located 2500 meters from Building A.
One (1) kilometer of cable is of buried armored construction and the other 1.5 kilometers is of aerial construction. Buildings A and B both have patch panels located where the fiber enters the building and patch cords or jumpers are used to connect the transmitters and receivers to the fiber backbone. The transmitters are modules, American Fibertek part MTM-300C and the receivers are rack mount, American Fibertek part RRM-300C. The connectors are ST type. There is a mechanical splice where the aerial and buried cables are connected.
SAMPLE CALCULATION
Loss Budget 12 dB
Operating Margin Allowance (-3 dB)
AFI recommends -3 dB
CABLE ATTENUATION
Armored Burial @ 3 dB/Km (-1.5 dB)
Aerial Cable @ 3 dB/Km (-2.3 dB)
SPLICE LOSS
Patch Panel Building A (-1.0 dB)
Mechanical (-0.5 dB)
Patch Panel Building B (-1.0 dB)
MARGIN 2.7 dB
The system still has 2.7 dB of available budget before you approach the operating margin. Calculating a system loss budget requires knowledge of the transmitter and receiver specifications as well as the cable infrastructure. Cable length, installation technique, number and type of splices, and equipment connector type must all be considered to engineer the system.
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