Cisco Cisco 40 Gigabit Modules 白皮書

Berk-Tek Leviton Technologies recently evaluated its premium OM3/OM4 and OM4+ components for 40 Gb/s Ethernet 
transmission using Cisco QSFP BiDi transceivers. Several channel configurations were tested, with Berk-Tek’s Micro Data 
Center Plenum (MDP) trunk cables and Leviton’s HDX MTP-LC multi-fiber cassettes. 

The objective was to simulate typical data center channel configurations and see if it was possible to achieve longer 
reach and more connections using premium grade OM4+ cabling.

The results indicate that the Berk-Tek Leviton Technologies data center products offer superior performance with Cisco 
QSFP BiDi transceivers. The reach and attenuation of the OM4+ channels exceed Cisco’s maximum recommendations 
for 40 Gb/s BiDi transceivers.

With capacity requirements increasing rapidly, more data centers are upgrading servers to 10 GbE from 1 GbE, and 40 GbE 
has become the most popular connection from the access switch to the aggregation layer. This migration is driving a need 
for higher port density on the switches, and several switch manufacturers are offering aggregation layer switches with only 
QSFP ports. One way to implement 40 Gb/s is through IEEE-standardized 40GBASE-SR4 technology, which uses four 10 Gb/s 
lanes each on an individual fiber and a multi-fiber cabling infrastructure. The complexity of transitioning the infrastructure 
from two-fiber duplex to multi-fiber cable might create some challenges for data center managers. However, Cisco is offering 
a 40 Gb/s transceiver that uses only two fibers and an LC duplex connection, instead of multi-fiber cable and connectivity 
with 40GBASE-SR4.

The Cisco BiDi transceiver is named after the bi-directional transmission in the optical channel. As shown in Figure 1, 
20 Gb/s data on two different wavelengths (between 832 nm and 918 nm) is transmitted in each fiber bi-directionally. 
The aggregated capacity of both the fibers is 40 Gb/s per direction.

20 Gb/s per wavelength transmission over LC multimode optical cable.

I 

1

 = 832 nm, I 

2

 = 918 nm 

I 

1

I 

1

I 

2

I 

2

The BiDi transceiver operates at a wavelength where the bandwidth is not specified in the ISO/IEC 60793 OM3/OM4 standard, 
and a direct correlation between fiber bandwidth (typically specified at 850 nm) and performance cannot be assumed. 
Cisco specifies  a maximum transmission distance of 100 meters and 150 meters over OM3 and OM4 
multimode fibers, respectively. 

In the TEK Center at Berk-Tek’s Pennsylvania headquarters, several tests were performed under various channel configurations 
on OM3, OM4 and OM4+ multimode fiber components to understand the maximum reach and connection limitations. 
The OM4+ fiber uses Berk-Tek GIGAlite-10XB glass.

1

 For a total channel insertion loss of 1 dB. 

2

 Cisco 40 Gigabit Modules QSFP Data Sheet.

APPLICATION NOTE

BerkTekLevitonTechnologies.com

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