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16 Feb 2016

With an increasing demand for more bandwidths, faster data rates and higher performance in telecommunication networks, the business case for 40 Gigabit Ethernet is becoming inescapably compelling. However, many users may feel confused when using 40G cables and optical transceivers. This article will solve the most frequently asked questions on Fiberstore’s 40G cabling and transceivers.

Q1: What 40G cables and transceivers are available from Fiberstore? 

Fiberstore supplies a full range of both copper cables and optical transceivers for 40GbE, compliant to the IEEE standards. For copper both QSFP+ to QSFP+ (40G to 40G) and QSFP+ to SFP+ (40G to 4x10G) cables enable short reach options. For longer distances, Fiberstore offers a wide range of optical transceivers for various fiber types and reach requirements.

Q2: What does the IEEE 40GBASE-X standard describe? 
The IEEE 40GBASE-X standard describes the following:
  • 40GBASE-SR4 It reaches 40-Gbps Ethernet over four short-range multimode fiber optic cables and supports link lengths of 100m and 150m respectively on laser-optimized OM3 and OM4 multimode fiber cables. In this process, the multimode fiber uses parallel-optics transmission instead of serial transmission due to the 850nm vertical-cavity surface-emitting laser (VCSEL) modulation limits. For example, Mellanox MC2210411-SR4 compatible 40GBASE-SR4 QSFP+ transceiver from Fiberstore supports link length of 100m over multimode fiber cable.
  • 40GBASE-LR4 It reaches 40-Gbps Ethernet over four wavelengths carried by a single long-distance singlemode fiber optic cable and supports link lengths of up to 10 km over single-mode fiber with duplex LC connectors. It operates at a wavelength of 1310 nm. The 40 Gigabit Ethernet signal is carried over four wavelengths with 10G on each wave.
  • 40GBASE-CR4 It is a direct attach cable segment with the QSFP+ modules attached to each end of the cable. It reaches 40-Gbps Ethernet over four short-range twinaxial copper cables bundled as a single cable and supports link lengths of up to 10 km over a standard pair of G.652 single-mode fiber with duplex LC connectors.

Q3: Can the 40G-LR4 transceiver be split into 4x10G connections? 

No, 40G-LR4 cannot be split into 4x10G. The 40GBASE-LR4 uses 4 lambdas (or wavelengths) on a pair of single mode fibers, and does not lend itself to “splitting” into 4 pairs without substantial complexity to split out the wavelengths. The unique characteristic of 40GBASE-SR4 is that it uses parallel (ribbon) fiber, which allows the creation of 4 fiber pairs. As an alternative single mode parallel 40G optics are available (40G-PLRL4 and 40G-PLR4) that do allow for splitting into 4x10G (single mode).

Q4: How does the QSFP+ to SFP+ fiber convertor allow 4x 10G? 

The IEEE 40G-SR4 standard specified a parallel technology, with 4 lanes in each direction. The purpose of this was to allow for easier development of 40G, re-using 10G components. As a side result the 40G multi-mode transceivers can also support 4x10G modes. A fiber that connects from one 40G port to four 10G ports provides a physical path to allow the source “40G” port running in 4x10G mode to be connected to 4 unique 10G destinations. As the fiber is a passive medium it has no concept of the 40G or 10G signals.

Fiberstore provides various types of 40G cables and transceivers including single-mode and multi-mode with different channels and wavelengths. All these transceivers are compatible with famous brands, like Brocade QSFP+, HP QSFP+, Juniper QSFP+, etc. They can also be customized to meet your special requirements.


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