Unearthing the basics of 40G QSFP (Quad Small Form-factor Pluggable Plus) Transceiver and Cabling.

With the quick development in data centre, Change has always remained a constant phenomenon. To meet the rapid increasing demand for higher bandwidth  data centre has gone  through great migration from 1G, 10G to 40G, 100G over the past few decades. Several types of 40G optical transceivers have been designed to achieve 40G network, of which QSFP is the most dominant  type available in the market. There are basic three 40G QSFP+ Optics for this standard: 40G LR4 QSFP+ transceiver, 40G SR4 QSFP+ transceiver and 40G LR4 parallel single mode (PSM) transceiver.

When the IEEE introduced the 802.3ba Ethernet standard in June 2010, this was in response to the increasing bandwidth demands facing data centers, paving the way for the introduction of 40Gb/s and 100Gb/s Ethernet operations

40G QSFP (Quad Small Form-factor Pluggable Plus) Transceiver

As we know, fiber optic transceiver is an electronic device that receives an electrical signal, converts it into a light signal, and launches the signal into a fiber. It also receives the light signal, from another transceiver, and converts it into an electrical signal. It is the key component in fiber optic transmission. The basic interface of 40G pluggable optical modules are 40GBASE-LR4 and 40GBASE-SR4 in QSFP+ form factor.

40G LR4 QSFP+ Transceiver

Conforming to the 802.3ba (40GBASE-LR4) standard, the 40G LR4 QSFP+ transceiver together with the LC connector can support an optical link length up to 10 kilometers over single mode fiber. 40G LR4 QSFP+ transceivers offer 4 independent transmit and receive channels. And to realize the function of transmitting the 4-channel signals over the single mode fiber, this kind of transceiver has to introduce MUX/DEMUX to multiplex/de-multiplex optical signals.

40G SR4 QSFP+ Transceiver

The 40G SR4 QSFP+ Transceiver (e.g. CiscoQSFP-40G-SR4), conforming to the 802.3ba (40GBASE-SR4) standard, provides a 40G optical connection using MPO/MTP fiber ribbon connectors. Unlike the 40G LR4 QSFP+ transceiver, this kind of transceiver are used together with multi-mode fiber, supporting with a link length up to 100 meters on OM3 cable and 150 meters on OM4 cable.

40G LR4 PSM Transceiver

The 40G LR4 PSM transceiver is designed with form factor, optical/electrical connection and digital diagnostic interface according to the QSFP+ MSA. As a highly integrated 4-channel optical module, this kind of transceiver can provide increased port density and total system cost savings. 40G LR4 PSM transceivers supports up to 10 kilometers over single mode fiber through MPO/MTP fiber ribbon connectors.

40G QSFP (Quad Small Form-factor Pluggable Plus) + Cables

QSFP  are the primary way of delivering 40GbE and are now appearing in 100GbE-capable form. These present either MPO connectors for multi-mode optics or LC connectors for single-mode optics.Indisputably, The Global Internet Protocol (IP) traffic has been experiencing a rapid increase in both the enterprise and consumer sectors.Significantly, these growth is been influenced  by the increasing  number of internet users and connected devices, faster wireless and fixed broadband access, high-quality video streaming, and social networking

To support the changing and fast-growing bandwidth demands of Data Centers (DCs), the IEEE recently ratified standards for supporting 40 Gigabit and 100 Gigabit Ethernet, known as IEEE 802.3ba. 40G module fibre optic cables are designed  faster, denser, bigger, more-cost-effective and more-power-efficient options for Data centres. Fibre optic lines are strands of optically pure glass as thin as a human hair that carry digital information over long distances. They are usually used in Telecommunication, medical imaging and mechanical engineering sectors.

40G cables are appreciated mostly because of its ability to  provide inexpensive and reliable 40G speed connections using either copper cables with distances reaching up to 30ft (~10 meters length) or active optical cables reaching even 300ft(100 meters).

40GbE solutions

40GbE (4×10GbE) QSFP+ optical transceivers include short-reach (SR4), long-reach (LR4) and extended long-reach (ER4). In many cases, 1GbE SFP and 10GbE SFP+ optics can be readily inserted, recognized, and utilized in the 40GbE QSFP+ receptacle through the use of a (QSA) pluggable adapter. The adapter supports standard SFP and SFP+ optics in a QSFP+ socket providing backwards compatibility, while preserving the 40GbE port for future bandwidth expansion.

Some similarities between 40Gbs and 100Gbs
1. Both 40Gbs & 100 Gbs Ethernet can be deployed using the same cabling systems in use today.
2. Polarity and gender are critically important features to consider when migrating from 10G to either 40G or 100G.
3. Skew has been shown to not be a factor in 40Gbs & 100Gbs Ethernet communications.
Conclusion
As mentioned above, Cabling deployed in the data center today must be selected to provide support of data rate applications of the future. To achieve this purpose, OM3 or OM4 is a must.Transceiver basicailly  serves as an ideal and feasible solution in situations where only limited fibers or limited conduit space is available. And the deployment of  transceivers efficiently enhances the bandwidth capacity of the existing optical fiber infrastructure and help to achieve the economic and reliable performance of the optical network.