This white paper introduces SFP+ Direct Attach Cables (DACs), which are crucial for addressing the increased bandwidth needs associated with server virtualization and data transmission in modern data centers. SFP+ DACs are cost-effective, low-power solutions that support 10 Gbps data rates and offer better cable management and reliability compared to optical transceivers. The document also outlines the different types of SFP+ cables, including passive and active copper cables, and active optical cables, detailing their specific use cases and advantages.

1. WHITE PAPER
Fiberstore White Paper | Introduction to SFP+ Direct Attach Cable 1
More bandwidth is needed to support the use of server virtualization. The amount and type of
devices residing on the network has also dramatically increased the amount of data that needs to
be transmitted to and from storage area networks (SANs). SFP+ direct attach cable (DAC), which
provides a lower-power means for operation on short fiber optic links or short copper connections,
has been a preferable solution to accommodate the ever-growing number of operating systems and
applications and the significantly increased data transmission between the servers and switches.
This post will give a brief introduction to SFP+ direct attach cable.
What Is SFP+ Direct Attach Cable?
First, we need to know what SFP+ direct attach cable is. It is a fixed assembly that is purchased at a
given length, with SFP+ connector modules permanently attached to each end of the cable. SFP+
direct attach cable uses an enhanced SFP+ connector to transmit and receive 10Gbps data through
one paired transmitters and receivers over a thin twinax cable or a fiber optic cable. It provides high
performance in 10 Gigabit Ethernet network applications. 10G SFP+ direct attach cable is designed
to use the same port as an optical transceiver, but compared with optical transceivers, the
connector modules attached to the cable leave out the expensive optical lasers and other electronic
components, thus achieving significant cost savings and power savings in short reach applications.
Advantages of SFP+ Direct Attach Cable
SFP+ direct attach cable is a low cost, low power consumption and low latency solution that is ideal
for high-density, in-rack 10Gbps connections between servers and switches. It provides better cable
management for high-density deployments and enhanced electrical characteristics for the most
reliable signal transmission. Here are several outstanding advantages of SFP+ direct attach cables.
 MSA compliant—fully conform to the SFP+ MSA specifications
 High speed—support 10 Gbps data rates with backwards compatibility to 1 Gbps
 Reliability—RoHS compliant with excellent EMI performance and high reliability
 Scalability and flexibility —provide enhanced scalability and flexibility, and higher density for
today's data centers and storage area networks
 Space saving—offer the smallest 10 gigabit form factor and a small overall cable diameter for
higher density and optimized rack space in 10G Ethernet uplinks and Fibre Channel
Introduction to SFP+
Direct Attach Cable

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Fiberstore White Paper | Introduction to SFP+ Direct Attach Cable 2
 Cost saving—cost up to three times less than fiber optic solutions, while offering lower latency
and consuming up to 50% less power per port than current copper twisted-pair cabling systems
Types of SFP+ Direct Attach Cable
Generally speaking, SFP+ direct attach cable can be divided into SFP+ direct attach copper cables
and SFP+ active optical cables (AOCs). This part will discuss these two kinds of SFP+ direct attach
cables.
There are two types of SFP+ direct attach copper cables, SFP+ active copper cable (ACC) and SFP+
passive copper cable (PCC). SFP+ passive copper cable (PCC), or passive SFP+ DAC, is fully compliant
to the SFF-8431 SFP+ MSA. It has no signal amplification in the cable assembly. When it is utilized,
electronic dispersion compensation (EDC) is typically used on the host board designs. EDC allows for
an extended length of passive cable assemblies. They deliver high-speed connectivity between
active equipment with SFP+ ports. The copper cable trunks are made to order, reducing installation
time and maximizing flexibility. The low power consumption assists in making the passive copper
cable assembly an economic solution for within rack or rack to rack applications. SFP+ active copper
cable (ACC) has signal amplification and equalization in the cable assembly. SFP+ ACC assemblies are
typically used in host systems that do not employ EDC. They also incorporate Rx LOS and Tx Disable
features. As with passive cables, the industry standard EEPROM signature enables the host system
to differentiate between an active copper cable and a fiber optic transceiver. The picture below
shows an HP JG081C compatible 10G SFP+ passive direct attach copper cable.
SFP+ active optical cable is composed of SFP+ optical transceivers in both ends and fiber optic cable
in between. This integrated optical module solution removes the complicated optical fiber interface
and brings friendly electrical-to-electrical interface to users. SFP+ AOC accepts the same electrical
inputs as a traditional copper cable. It uses optical fiber and electrical-optical conversion on the
cable ends to improve speed and data transmission distance of the cable while not sacrificing
compatibility with standard electrical interfaces. SFP+ AOC is designed to meet the requirements of
high speed, high density and low power consumption for applications in today's data centers via

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Fiberstore White Paper | Introduction to SFP+ Direct Attach Cable 3
optical fiber wire. It has been a preferable interconnect solution for SFP+ applications. SFP+ AOC is
compliant to industrial standard SFP MSA and provides high performance SFP+ interfaces,
supporting 10Gb/s bi-directional operation. The image below shows a Cisco SFP-10G-AOC10M
compatible 10G SFP+ active optical cable.
Conclusion
SFP+ direct attach cable provides a cost-effective and low power consumption solution for
high-density 10 Gigabit connections. These three types of 10G SFP+ direct attach cable assemblies,
10G SFP+ passive copper cable (PCC), 10G SFP+ active copper cable (ACC), and 10G SFP+ active
optical cable (AOC) are of their special applications. SFP+ direct attach cable has a lot of advantages.
It now has been a very popular choice in the market.

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Fiberstore White Paper | Introduction to SFP+ Direct Attach Cable 4
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Notice: This document is for informational purposes only and does not set forth any warranty, expressed or
implied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.
Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes no
responsibility for its use. This information document describes features that may not be currently available.
Contact a Fiberstore sales team for information on feature and product availability.
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