Chapter 1 Overview
Front-Panel Description
SFP Modules
The Catalyst 2940-8TF-S switch uses a field-replaceable SFP module to establish Gigabit connections. You insert an SFP module into the SFP module slot on the front of the switch.
The Cisco SFP modules that are supported by the Catalyst 2940-8TF-S switch include:
•1000BASE-LX, fiber-optic
•1000BASE-SX, fiber-optic
•1000BASE-T, copper
•Coarse Wavelength-Division Multiplexing (CDWM), fiber-optic
Note The Catalyst 2940-8TF-S switch only supports 1000 Mbps and full-duplex modes on SFP modules.
The 1000BASE-LX and 1000BASE-SX SFP modules are used to establish fiber-optic connections. You use fiber-optic cables with LC connectors to connect to an SFP module. The SFP modules support 850 to 1550 nm nominal wavelengths. These field-replaceable modules provide the uplink optical interfaces, laser send (TX), and laser receive (RX).
The restrictions are that each port must match the wave-length specifications on the other end of the cable, and the cable must not exceed the stipulated cable length for reliable communications. Table 1-3lists these stipulations.
Table 1-3 Cabling Stipulations for Fiber-Optic SFP Modules
| | | | | | 8 micron |
| 62.5/125 micron | 50/125 micron | 62.5/125 micron | 50/125 micron | 9/125 micron | Single-mode |
SFP | Multimode | Multimode | Multimode | Multimode | Single-mode | Dispersion |
Module | 850 nm1 Fiber | 850 nm Fiber | 1310 nm Fiber | 1310 nm Fiber | 1310 nm Fiber | Shifted Fiber |
SX | 275 m2 at | 550 m at | | | | — |
| 200 Mhz-km | 500 Mhz-km | | | | |
| | | | | | |
LX | — | — | 550 m at | 550 m at | 10 km | — |
| | | 500 Mhz-km | 400 Mhz-km | | |
| | | | | | |
CWDM3 | 1470, 1490, 1510, | SMF | 9/125 | — | 62 miles (100 | 1470, 1490, |
| 1530, 1550, 1570, | | | | km) | 1510, 1530, |
| 1590, 1610 | | | | | 1550, 1570, |
| | | | | | 1590, 1610 |
| | | | | | |
1.nm = nanometer
2.m = meter
3.CWDM = Coarse Wavelength-Division Multiplexing
The 1000BASE-T SFP module is used to establish a Gigabit Ethernet connection through a Category 5 (copper) cable. This module can provide a Gigabit Ethernet connection of up to 100 meters through a Category 5 cable.
Use only Cisco SFP modules on the Catalyst 2940-8TF-S switch. Each SFP module has an internal serial EEPROM that is encoded with security information. This encoding provides a way for Cisco to identify and validate that the SFP module meets the requirements for the switch.
Catalyst 2940 Switch Hardware Installation Guide
