IBM ATM OC-3c manual Does the Cable Provide Sufficient Bandwidth?, Specification Description

C-2APPENDIX C: ATM MODULE TECHNICAL SPECIFICATIONS

Table C-2Standard Multi-mode Cable Specifications

Specification	Description
Core	62.5μm diameter
Cladding	125μm diameter nominal
	122μm minimum
	128μm maximum
Numerical aperture	0.275
Maximum attenuation	11dB (including 1dB allowed for
	reflection and dispersion penalties)
Modal bandwidth	500 MHz.km
Maximum distance between	2km (1.25 miles)
nodes
Output power (from transceiver)	-20dB minimum
	-14dB maximum
Receiver power	-31dB minimum sensitivity
	-14dB maximum sensitivity

Maximum attenuation includes attenuation and the loss induced by other components such as connectors, splices, and the mating of unlike fiber types. Although some 2km (1.25 miles) cables have a total attenuation of less than 11dB, the 2km (1.25 miles) inter-station distance must be maintained to comply with modal bandwidth requirements.

The maximum attenuation value in this table is based on a cable diameter of 62.5, 80 or 100mm.

Table C-3 shows the alternative Multi-Mode fiber types that can be used.

Table C-3Alternative Multi-mode Cable Specifications

Core (2m)	Cladding (2m)	Numerical Aperture
50	125	0.20
50	125	0.22
85	125	0.28
100	140	0.29

If you are using fiber with a diameter of 50mm and have IBM 8271 Nways Ethernet LAN Switch equipment at both ends of the link, substitute 8.0dB for the maximum attenuation. If IBM 8271 Nways Ethernet LAN Switch equipment is only at one end, substitute 6.0dB for the maximum attenuation value.

If you are using equipment at the end of the link from a vendor other than IBM, you must perform a separate loss budget analysis. Contact the vendor(s) for values to use in your analysis.

Does the Cable Provide Sufficient Bandwidth?

Bandwidth for multi-mode fiber is referred to as modal bandwidth because it varies with the modal field (or core diameter) of the fiber.

Modal bandwidth is specified in units of MHz.km, which indicates the amount of bandwidth supported by the fiber for a 1km (0.625 miles) distance. Your cable must have a Modal bandwidth of 500MHz, which allows the cable to support end-to-end bandwidth of 250MHz at the maximum 2km (1.25 miles) distance.