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FAQ - Can a GE Optical Module Interconnect with a FE Optical Module

Publication Date:  2013-09-22 Views:  101 Downloads:  0
Issue Description

Background: A customer purchases Huawei NE40E that uses line cards providing GE optical ports. The GE optical modules fail to interconnect with 100M optical modules on customer's existing devices.

The customer asks why the GE and 100M optical module fail to negotiate rates and why they cannot interconnect with each other?
Handling Process

1. According to IEEE 802.3, unlike electrical port auto-negotiation, optical port auto-negotiation does not involve rates. The following figures compare auto-negotiation information between optical ports and electrical ports.

Figure 1 Description about auto-negotiation information about optical ports in IEEE 802.3



Figure 2 Description about auto-negotiation information about electrical ports



2. Light emitting components in optical modules emit light at a fixed rate.

A 1000 Mbit/s optical module emits light at a rate of 1000 Mbit/s and a 100 Mbit/s optical module emits light at a rate of 100 Mbit/s. Being interconnecting with a 1000 Mbit/s optical module, a 100 Mbit/s optical module cannot receive information from the 1000 Mbit/s optical module and therefore cannot establish a connection. Even if the GE optical module is forcibly configured to work in 100M mode, it cannot interconnect with the FE optical module.
Root Cause

Replace the GE optical modules on NE40E with 100M optical modules.

Huawei line cards' GE ports support automatic rate adaptation.

After housing a 100M optical module, the port automatically changes the bandwidth to 100 Mbit/s and works in 100M mode.
Only optical modules with the same rate can interconnect with each other.