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Link Power Budget
1) In a singlemode fiber optic circuit, he link loss on a fiber strand, expressed in dB, worst case of amplitude loss measurements taken in both directions at 850 nm, 1310 nm, and 1550 nm optical frequency spectra, or 2) In a fiber optic transceiver, the difference expressed in dB between the Minimum Output Power of the transmitter and the Minimum Sensitivity of the receiver. Devices having a Link Power Budget capability equal to or in excess of the worst-case link loss measurement of a singlemode fiber optic circuit will operate on that circuit. (Gigabit Ethernet, with its narrow bit-time window, also requires that phase jitter be well-controlled.) This is a more accurate measurement than the manufacturer-expressed distances nominally provided in product descriptions of fiber optic singlemode media conversion and switching products, since the number of splices, patch panels, curves in the fiber strands and other circumstances provide varying amounts of signal loss. Devices having identical Link Power Budget specifications will be able to span identical distances on a singlemode fiber optic circuit, regardless of the distance nominally specified for a particular unit. Signamax media converters and fiber optic switch interfaces are normally specified extremely conservatively, so that the claimed distances can be achieved on singlemode fiber optic circuits with many splices, patch panels, or bends in the fiber optic strands.