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The WS-G5487, 1000BaseZX operates on ordinary single mode fiber optic link spans of up to 70 km in length. Link spans of up to 100 km are possible using premium single mode fiber or dispersion shifted single mode fiber (premium single mode fiber has a lower attenuation per unit length than ordinary single mode fiber; dispersion shifted single mode fiber has both lower attenuation per unit length, and less dispersion).

The WS-G5487 must be coupled to single mode fiber optic cable, which is the type of cable typically used in long haul telecommunications applications. The WS-G5487 will not operate correctly when coupled to multi-mode fiber, and it is not intended to be used in application environments (e.g. building backbones, horizontal cabling) where multi-mode fiber is frequently used.

The WS-G5487 is intended to be used as a Physical Medium Dependent (PMD) component for Gigabit Ethernet interfaces, as found on various switch and router products. It will operate at a signaling rate of 1250 MBaud, transmitting and receiving 8B/10B-encoded data. When shorter distances of single mode fiber are used, it may be necessary to insert an in-line optical attenuator in the link, to avoid overloading the receiver. A 10 dB in-line optical attenuator should be inserted between the fiber optic cable plant and the receiving port on the WS-G5487 GBIC at each end of the link whenever the fiber optic cable span is less than 25 km. A 5 dB in-line optical attenuator should be inserted between the fiber optic cable plant and the receiving port on the WS-G5487 GBIC at each end of the link whenever the fiber optic cable span is equal to or greater than 25 km, and less than 50 km.