As the fast development of Gigabit Ethernet, 10Gbps cannot satisfy the users anymore, especially for some medium and large enterprises. Traditionally, it would cost a lot to update your network. It refers to a large range of things—cables, transceivers, switches and etc. But now, it would not be a problem with innovative 40Gbps Quad Small Form-Factor Pluggable (QSFP) bidirectional (BiDi) technology. That allows reuse of reuse of existing 10Gbps fiber infrastructure for 40Gbps connections. We would give further explanation and demonstration in the following passage.
Figure1: 40G QSFP BiDi transceiver in Cisco Switch
We would basically clarify this part from the aspect of connectors and fiber strands.
10G SR SFP+ and 40G QSFP SR transceivers use basically different connectivity formats. 10GBASE SR transceivers transmit data over mutimode fiber with LC connectors while 40GBASE SR4 transceivers over ribbon mutimode fiber with MPO connectors. As a consequence, 40G MPO-based SR4 transceivers cannot reuse aggregation fiber infrastructure built for 10G connectivity. That means we need to redesign and replace the fiber cabling infrastructure.
10GBASE SR transceivers require 2 fiber strands per 10Gbps link while 40GBASE SR4 transceivers require at least of 8 fiber strands, and often 12 fiber strands in practice. The reason for this requirement is that 40G SR4 use 4 parallel fiber pairs (8 fiber strands) at 10Gbps each for a total of 40Gbps full duplex, as shown in Figure 2. The 40G transceivers use MPO-12 connectors terminated with 12-fiber ribbons. In this way, 4 fiber strands in each connection are unused and wasted.
Figure2: Principles of 40G QSFP+ transceiver
The 40G QSFP BiDi transceiver is a pluggable optical transceiver with a duplex LC connector interface for transmission within short distance over multimode fiber. It transmits fully duplex 40G data via OM3 or OM4 multimode fiber cable with one duplex LC connector. This makes it easier to reuse 10G fiber infastructure to migrate 10G to 40G network. In this way, the data center operators could make 10G to 40G migration without making ant changes to the previous 10G fiber cable plant. It offers a compelling solution that enables reuse of their existing 10G duplex multimode infrastructure for migration to 40G Ethernet connectivity.
Figure3: Principles of 40G QSFP BiDi transceiver
The 40G QSFP BiDi transceiver consists of two 20G transmit and receive channels in the 832-918 nanometer wavelength range, each transmitted and received simultaneously over two wavelengths on a single multimode fiber strand. As a consequence, an aggregated duplex 40-Gbps link can be achieved over a multimode duplex LC-terminated fiber cable. The link lengths of 40G QSFP+ transceiver can be up to 100 and 150 meters respectively on laser-optimized OM3 and OM4 multimode fiber.
As is known to all, networking devices can be directly connected with fiber cables. This direct connection design can be used to connect devices within short distance in an unstructured cabling system. Direct connection between two 40G transceivers can be provided by multimode cables with either QSFP SR4 or QSFP BiDi transceivers at two ends, just shown as the following figure.
Figure4: 40G direct connection
The Cisco QSFP BiDi transceiver uses LC connectors while QSFP SR4 uses MPO-12 fiber connectors. None of the existing 10G multimode cables can be reused with QSFP SR4 transceivers, because the two connectors are completely not matched at all. With Cisco QSFP BiDi transceiver, the cable can be reused for the same type of connectors. As a result, it would bring zero-cost cabling migration from direct 10Gbps connections to direct 40Gbps connections. Therefore, in comparison to QSFP SR4 transceivers, Cisco QSFP 40G BiDi short reach transceives reduce costs by 100 percent.
40G QSFP BiDi transceiver provides the most cost-effective solution for 10G to 40G network migration. By transmitting full-duplex 40 Gigabit Ethernet over a duplex multimode fiber, it helps enable seamless 10 to 40 Gigabit Ethernet migration over your 10 Gigabit Ethernet fiber infrastructure in a zero cost cabling. If you need 40G QSFP transceivers, you can take FS a try. We offer not only the mentioned QSFP SR4, QSFP BiDi transceivers, but the many other standard 40G QSFP transceivers with high quality but low cost. For more details, please visit our website.