3Com 7000 manual Comparing Fiber to Specifications

112APPENDIX D: CABLING REQUIREMENTS

Multi-mode Fiber The MMF-PMD standards define the requirements for an ATM cable plant Standards to support an interstation distance of up to 2 kilometers (1.25 miles) of

multi-mode fiber. The cable plant includes all fiber optic components between any two communicating ATM devices and their associated “station-to-network” connectors at each end.

To determine whether the cable plant complies with the MMF-PMD standard, do the following:

1Compare the specifications of the fiber you are using to standard specifications, as described in Table 25 and Table 26.

2If unlike fibers are mated in the cable plant, calculate insertion losses to see whether they exceed the maximum attenuation value allowed for a link, as described in Table 27 and Table 28.

3Verify that the fiber's modal bandwidth is within an acceptable range for the length of the link, as described on page 115.

The following sections describe each of these steps and give examples.

Comparing Fiber to Specifications

Compare the specifications of the fiber you are using to those in the following tables. If the fiber does not meet the specifications, use a different fiber or contact 3Com's Technical Support.

The fiber you use must meet the specifications listed in Table 25, which describes the standard set forth in MMF-PMD. Table 26 describes 62.5/125 cable, commonly sold as “ATM Spec,” which meets all the requirements of the MMF-PMD standard.

Table 25 Standard Multi-mode Fiber Specification

Specification	Description
Core	62.5 µm diameter
Cladding	125	µm diameter nominal
	122	µm minimum
	128	µm maximum
Numerical aperture	0.275
Maximum attenuation	11 dB* (1dB allowed for reflection and
	dispersion penalties.)
Modal bandwidth	500	MHz. km