Cisco Cisco DWDM Transceiver Modules 白皮書

 

 

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White Paper 

Migrate to a 40-Gbps Data Center with Cisco QSFP 
BiDi Technology 

 

What You Will Learn 

This document describes how the Cisco

®

 40-Gbps QSFP BiDi transceiver reduces overall costs and installation 

time for customers migrating data center aggregation links to 40-Gbps connections. 

As a result of data center consolidation, server virtualization, and new applications that require higher data 

transport rates, the data center network is shifting to 10 Gbps at the access layer and 40 Gbps at the aggregation 

layer. A broad portfolio of high-performance and high-density 10- and 40-Gbps Cisco Nexus

®

 Family switches is 

available at attractive prices for this transition. However, to support 40-Gbps connectivity, data center architects are 

challenged by the need for a major upgrade of the cabling infrastructure, which can be too expensive or disruptive 

to allow data centers to quickly adopt and migrate to the 40-Gbps technology. 

Cisco solves this problem with innovative 40-Gbps Quad Small Form-Factor Pluggable (QSFP) bidirectional (BiDi) 

technology that allows reuse of existing 10-Gbps fiber infrastructure for 40-Gbps connections. 

Challenges with Existing 40-Gbps Transceivers 

Standard short-reach (SR) 10- and 40-Gbps transceivers use fundamentally different connectivity formats, 

requiring fiber cabling infrastructure to be redesigned and replaced. 10-Gbps SR transceivers operate over dual-

fiber multimode fiber (MMF) with LC connectors, and 40-Gbps SR protocols, such as SR4 and CSR4, operate over 

MMF ribbon with MPO connectors. As a result, 40-Gbps MPO-based SR4 transceivers cannot reuse aggregation 

fiber infrastructure built for 10-Gbps connectivity. 

Connector type is not the only concern. Whereas 10-Gbps SR transceivers require 2 fiber strands per 10-Gbps 

link, 40-Gbps SR4 and CSR4 transceivers require a theoretical minimum of 8 fiber strands, and often 12 fiber 

strands in practice. The reason for this requirement is that 40-Gbps SR4 and CSR4 use 4 parallel fiber pairs (8 

fiber strands) at 10-Gbps each for a total of 40-Gbps full duplex, as shown in Figure 1. However, both use MPO-12 

connectors, which terminate 12-fiber ribbons. As a result, 4 fiber strands in each connection are unused and 

wasted.