Tag Archives: Active optical cable

Choice of Bidirectional Transceivers for 40 GbE

As a result of data center consolidation, server virtualization, and new applications that require higher data transport rates, 10Gbps infrastructure is becoming overwhelmed by today’s data center requirements, making the shift to 40 and 100 Gbps inevitable, especially in the network aggregation layer and core. How to upgrade the cabling infrastructure and migrate to the 40Gbps era in a cost-effective way? Cisco 40G QSFP (quad small form-factor pluggable) bidirectional (BiDi) technology provides a feasible and effective method, which will be introduced in the following text.

What Is 40G QSFP BiDi Transceiver?

Cisco’s innovative 40 Gbps QSFP BiDi transceiver is a pluggable optical transceiver with a duplex LC connector interface for short-reach data communication and interconnect applications. The Cisco BiDi transceiver supports link lengths of 100m and 150m on laser-optimized OM3 and OM4 multimode fibers. It complies with the QSFP MSA specification, enabling customers to use it on all QSFP 40 Gbps platforms to achieve high-density 40 Gigabit Ethernet networks.

How Does 40G QSFP BiDi Transceiver Work?

Cisco QSFP BiDi transceiver technology converts four channels each of 10Gbps transmit and receive signals to two bidirectional channels of 20Gbps signals, which means that the Cisco QSFP BiDi transceiver has two 20Gbps channels, each transmitted and received simultaneously over two wavelengths on a single MMF strand. The technology uses specialized, multilayer, thin-film dielectric coating and lensing, which allows components to both pass and reflect optical signals at the same time. And it uses Bidirectional Optical Sub-Assembly (BOSA) technology to support two wavelengths (20 Gbps total) on each fiber. The connection can reach 100 meters on OM3 MMF or 150 meters on OM4 MMF, which is the same as 40Gbps SR4. Picture below shows the technology concept of the Cisco QSFP BiDi transceiver.

Concept of Cisco QSFP BiDi Transceiver

Why Choose 40Gbps QSFP BiDi Transceiver?

The Cisco QSFP BiDi transceiver transmits full-duplex 40Gbps traffic over one dual-fiber LC connector OM3 or OM4 MMF cable. It provides the capability to reuse 10Gbps fiber infrastructure. In other words, it enables data center operators to upgrade to 40Gbps connectivity without making great changes to the previous 10Gbps fiber cable plant. By using the existing 10 Gigabit Ethernet duplex multi-mode fiber (MMF) infrastructure for 40 Gigabit Ethernet, the Cisco BiDi transceiver offers significant cost savings and simplifies data center upgrading. It allows for zero-cost fiber migration by reusing the current 10Gbps cabling for 40Gbps device connectivity. 40Gbps QSFP BiDi transceiver reduces overall costs and installation time for customers migrating data center aggregation links to 40Gbps connections. Using Cisco BiDi transceivers offers 75% less fiber and MPO requirements, reduced cable sprawl and rack footprints, and investment protection with future support for 100 Gbps over duplex fiber.


Cisco 40G QSFP BiDi technology removes 40Gbps cabling cost barriers for migration from 10Gbps to 40Gbps connectivity in data center networks. It is quite a competitive option among all those various choices for 40 Gigabit Ethernet applications, such as QSFP+ transceiver, QSFP+ breakout cable or active optical cable. Compared with them, Cisco 40G QSFP BiDi transceivers provide simpler and less expensive 40Gbps connectivity compared to other 40Gbps transceiver solutions. Anyway, you choose the most appropriate one for your applications.

The Basics of Dirrect Attach Cables

Dirrect attach cable (DAC), is a cost effective and proven solution for interconnecting networking applications. It can provide inexpensive and reliable connections using either copper cables or fiber cables. What is DAC? How copper DAC and fiber DAC differ from each other? Here is what you need to know about DACs.

DAC Definition

A direct attach cable is a fixed assembly that is purchased at a given length, with the connector modules permanently terminated to each end of the cable to connect switches to routers or servers. DACs are much cheaper than the regular optics, since the “transceivers” on both ends of DACs are not real optics and their components are without optical lasers. They are preferable choice for their low cost, low power consumption and high performances. DAC are made of the two kinds of cable materials: copper and optical fiber. They are respectively called direct attach copper cable and active optical cable.

DAC Assemblies—Copper

Direct attach copper cable is interchangeable and hot swappable with fiber optic modules. It is designed in either active or passive versions. It supports such multiple protocols as Gigabit & 10G Ethernet, 8G FC, FCoE and InfiniBand. Direct attach copper cable is a cost effective solution over optical transceivers and and cables for short reach applications. It can support higher data rates than traditional copper interfaces—from 4Gbps to 10Gbps per channel. The defect of direct attach copper cable is that it is heavy and bulky, making it difficult to be managed. Furthermore, due to the nature of electrical signals, direct attach copper cable is vulnerable to the effects of electromagnetic interference (EMI), such as undesirable responses, degradation, or complete system failure. Fiberstore offers various QSFP+ direct attach copper cables with different lengths for your 40G applications. For example, lengths of Juniper EX-QSFP-40GE-DAC-50CM, QFX-QSFP-DAC-1M and QFX-QSFP-DAC-3M compatible QSFP+ to QSFP+ passive copper cables are respectively 0.5m, 1m, and 3m.

0.5m Juniper EX-QSFP-40GE-DAC-50CM Compatible QSFP+ to QSFP+ Passive Copper Cable

DAC Assemblies—Fiber

Active optical cable (AOC) is an alternative to optical transceivers, eliminating the separable interface between transceiver module and optical cable. It meets Small Form-factor (SFF) standards. Compaired to direct attach copper cable, AOC weighs less and can support longer transmission distance. It is immune to electromagnetic energy since the optical fiber is dielectric (not able to conduct electric current). What’s more, it is an alternative to optical transceivers and it can eliminate the separable interface between transceiver module and optical cable. AOC has no EMI. However, it costs more than copper cable.


Applications of DAC

Direct attach cables are widely applied in storage area network, data center, and high-performance computing connectivity. They suppoet high speed I/O applications in storage, networking and telecom markets. And they can also be sused in witches, servers, routers, network interface cards (NICs), and Host Bus Adapters (HBAs). There are many different kinds of DACs, they all have their specific applicayions. For example, 40G AOC is commonly used for short-range multi-lane data communication and interconnect applications.


Fiberstore offers a variety of high speed interconnect DAC assemblies including 10G SFP+ cables, 40G QSFP+ cables, and 120G CXP cables to satisfy the demands from 10G to 100G interconnection. Direct attach cables provided by Fiberstore can be customized to meet different requirements. And we also offer all kinds of high quality QSFP+ modules branded by many famous companies, like Brocade QSFP+, Dell QSFP+, Juniper QSFP+, Finisar QSFP+, Intel QSFP+, etc. You can buy from us with confidence.