Types of QSFP Transceivers

In order to meet the demand for increasing the transceiver port density for optical applications and find a cost effective way to increase date rate, multiple communications companies announced the release of a quad small form-factor pluggable (QSFP) optical module specification in its final form in December 4, 2006. The QSFP specification defines a highly integrated four-channel optical transceiver to provide increased port density and total system cost savings when replacing four standard SFP transceiver modules. The 40GBASE QSFP module has become a dominant 40G optical transceiver and offers customers a wide variety of high-density 40 Gigabit Ethernet connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, and service provider transport applications.

There are various kinds of QSFP transceivers for different distance requirements and fiber types. According to various criteria, QSFP transceivers can be divided into different types.

Transport Media

Copper, single mode fiber (SMF) and multimode fiber (MMF) are three kinds of transport media used in 40 Gigabit Ethernet. Different QSFP transceivers may adopt different transport media. According to IEEE Ethernet standard, the followings are commonly used 40 Gigabit Ethernet media system:

QSFP-40G-CR4—40 Gigabit Ethernet over four short-range twinaxial copper cables bundled as a single cable.

QSFP-40G-SR4—40 Gigabit Ethernet over four short-range multimode fiber optical cables.

QSFP-40G-LR4—40 Gigabit Ethernet over four wavelengths carried by a single long-distance single mode fiber optical cable.

Connector Type

Different QSFP transceivers may have different connector interfaces. Through various technologies, many kinds of connectors could be applied into 40 Gigabit Ethernet. And the commonly-used are Duplex LC, MPO and MPO/MTP. MPO and MTP are often used interchangeably. For example, Fiberstore QSFP-40G-SR4 and QSFP-40G-LR4 are transceivers with duplex LC connectors. While the Cisco QSFP-40G-CSR4 is with MPO/MTP connector.

Transmission Distance

According to transmission distance, QSFP transceivers can be divided into short-range QSFP transceiver and long-range QSFP transceiver. QSFP-40GBD-SR is among the various short-range QSFP transceivers. It supports link lengths of 100 meters and 150 meters over laser-optimized OM3 and OM4 multi-mode fibers respectively. As a long-range QSFP transceiver, QSFP-40G-ER4 has a transmission distance of 40 km.

Wavelength

In a QSFP transceiver, the wavelength of each channel can either be of the same or differs from each other. For instance, The wavelengths of Cisco QSFP-40G-SR4 and Cisco QSFP-40G-CSR4 transceivers are 4×850nm. While the four lanes of QSFP-40G-ER4 are 1271nm, 1291nm, 1311nm and 1331nm respectively.

The QSFP specification accommodates Ethernet, Fibre Channel, InfiniBand and SONET/SDH standards with different data rate options. The QSFP transceiver modules can be connected to both copper and optical cables. In the process of transmitting data,the QSFP transceiver converts parallel electrical input signals into parallel optical signals by a driven Vertical Cavity Surface Emitting Laser (VCSEL) array. All data signals are differential and the data rate can be up to 10 Gbps per channel. As the QSFP transceivers are used to interface networking hardware to a fiber optic cable, the choice of them depends on many factors, like the transport media, the connector type, transmission distance, wavelength, etc.

QSFP Transceiver Overview

In order to find a cost effective way to increase date rate, multiple communications companies announced the release of a quad small form-factor pluggable (QSFP) optical module specification in its final form in December 4, 2006. The QSFP specification defines a highly integrated four-channel optical transceiver to provide increased port density and total system cost savings when replacing four standard SFP transceiver modules. Since then, the 40GBASE QSFP module has become a dominant 40G optical transceiver and offers customers a wide variety of high-density 40 Gigabit Ethernet connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, and service provider transport applications.

What Is QSFP Transceiver

QSFP transceiver module is a hot-swappable, parallel fiber-optical module with four independent optical transmit and receive channels. These channels can terminate in another 40-Gigabit QSFP transceiver, or the channels can be broken out to four separate 10-Gigabit SFP+ transceivers. For instance, QSFP-40G-SR provides four channels of data in one pluggable interface and each channel is capable of transferring data at 10 Gbps and supports a total of 40 Gbps. QSFP transceiver is an industry format jointly developed and supported by many network component vendors, allowing data rates from 4x10 Gbps. The QSFP product family includes cages in single and ganged configurations with various heat sink and lightpipe options. It uses 38 position connector and Electro Magnetic Interference (EMI) plugs are offered for empty ports to interface networking hardware to a fiber optic cable.

Advantages of QSFP Transceiver

The QSFP transceiver is designed with form factor, optical/electrical connection and digital diagnostic interface according to the QSFP Multi-Source Agreement (MSA). It has been designed to meet the harshest external operating conditions including temperature, humidity and EMI interference. The module offers very high functionality and feature integration, accessible via a two-wire serial interface. The quad small-form-factor pluggable (QSFP) is a full-duplex optical module with four independent transmit and receive channels designed to replace four single-channel SFPs in a package only about 30% larger than the standard SFP. The port density is three times higher than traditional SFP designs. As a result, the QSFP transceiver offers customers a wide variety of high-density and low-power 40 Gigabit Ethernet connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, and service provider applications.

Applications of QSFP Transceiver

The QSFP specification accommodates Ethernet, Fibre Channel, InfiniBand and SONET/SDH standards with different data rate options. The QSFP transceiver modules can be connected to both copper and optical cables. In the process of transmitting data, the QSFP transceiver converts parallel electrical input signals into parallel optical signals by a driven Vertical Cavity Surface Emitting Laser (VCSEL) array. All data signals are differential and the data rate can be up to 10 Gbps per channel. As the QSFP transceivers are used to interface networking hardware to a fiber optic cable, the choice of them depends on many factors, like the transport media, the connector type, transmission distance, wavelength, etc. For example, Fiberstore provides various kinds of QSFP transceivers like Cisco QSFP-40G-ER4 compatible 40GBASE-ER4 transceiver which supports link lengths of 40 km on single-mode fiber cable at a wavelength of 1310nm.

QSFP transceivers supplied by Fiberstore offer customers a wide variety of high-density and low-power 40 Gigabit Ethernet connectivity options for data center, high-performance computing networks, enterprise core and distribution layers, as well as service provider applications.

How to Choose the 40G Transceivers

With the economics-driven growth of global regional and local fiber communication network over the past few decades, the IEEE 802.3 ba 40Gb/s Ethernet standard was published in June, 2010. In order to meet the data transmission needs in the market, a high-performance and flexible implementation of the IEEE 802.32012 for 40Gbps Ethernet - 40GBase optical transceivers are developed and widely used. The 40GBase optical networking equipment transfers data at a rate of 40 gigabits per second over Ethernet.

40GBase optical transceivers, compliant to the IEEE standards mainly include CFP and QSFP (quad small form-factor pluggable). Today, let’s mainly discuss on how to choose the 40G QSFP transceiver. As the 40-Gigabit QSFP transceivers are used to interface networking hardware to a fiber optic cable, the choice of them depends on many factors, like the media system, the connector type, transmission distance, wavelength, etc. Thus we should consider all these factors comprehensively before we choose the 40G QSFP transceivers.

Transport Media

Choose the right transceivers according to the transport media, namely the fiber type. According to the IEEE 802.3 ba 40Gb/s Ethernet standard, there are three types of transceivers used respectively in three types of transport media: copper, single mode fiber (SMF) and multimode fiber (MMF).

• Copper: 40GBASE-CR4 is a direct attach cable segment with the QSFP+ modules attached to each end of the cable. It reaches 40 Gb/s Ethernet over four short-range twinaxial copper cables bundled as a single cable over a standard pair of G.652 single-mode fiber. For example, Juniper EX-QSFP-40GE-DAC-50CM compatible QSFP+ to QSFP+ copper direct attach cable is suitable for very short distances and offers a very cost-effective way to establish a 40-Gigabit link between QSFP ports of Juniper switches within racks and across adjacent racks.
• SMF: 40GBASE-LR4 transceiver reaches 40 Gb/s Ethernet over four wavelengths carried by a singlemode fiber optic cable.
• MMF: 40GBASE-SR4 transceiver reaches 40 Gb/s Ethernet over four short-range multimode fiber optic cables.

Connector Type

Choose the right transceivers which are compliant with the proper connectors. The connectors widely-used mainly have following types: Duplex LC connector, MPO connector, and MTP connector (a high performance MPO connector). For instance, Cisco QSFP-40GBD-SR transceiver is compliant with the Duplex LC connector, while Arista QSFP-40G-PLR4 transceiver is compliant with the MPO connector.

Transmission Distance

When we choose the ideal transceivers, we must consider the transmission distance and the reach requirements we need in reality. The most common types of transceivers divided by its transmission distance can reach up to 100m, 150m, 300m, 400m, 1km, 2km, 10km, 40km, etc. For example, Cisco QSFP-40G-CSR4 compatible QSFP+ transceiver provided by Fiberstore supports link lengths of 82m, 300m and 400m, respectively on OM2, OM3 and OM4 multimode fibers at a wavelength of 850nm. And some others, like QSFP-40G-ER4 transceiver which supports link lengths of 40km on single-mode fiber cable is designed to use in long distance transmission.

Wavelength

The wavelength the transceivers operate with is an important factor in choosing the proper transceivers. For instance, QSFP-40G-LX4 transceiver converts 4 inputs channels (1271nm, 1291nm,1311nm, 1331nm) of 10Gb/s electrical data to 4 CWDM optical signals, and multiplexes them into a single channel for 40Gb/s optical transmission. While some other transceivers like QSFP-40GBD-SR consists of two 20-Gbps transmit and receive channels in the 832-918 nm wavelength range.

Fiberstore provides various types of 40G QSFP transceivers including single-mode and multi-mode with different channels and wavelengths. In order to achieve a fast and successful selection of the 40G QSFP transceivers, we should consider all the above-mentioned factors comprehensively.