QSFP+ is a type of pluggable transceiver used to connect a network device to a copper or fibre optic cable. They are the evolution of SFP and QSFP and are most often used for ethernet and high-speed data communications applications. So, what are they and how do they work? In this article, we will explain everything you need to know.
One of the key requirements for the success of any modern data centre is its ability to transmit huge amounts of data as quickly as possible. This is where transceivers such as SFP, SFP+, QSFP and QSFP+ are invaluable in the networks they are deployed in.
They can serve a range of purposes from bridging network switches without the need for bulky equipment, or when used in a fibre optic network they excel at transmitting data over long distances through fibre optic cables without losing signal integrity.
One of the most commonly used types of transceivers is QSFP+. Released in 2012, QSFP+ was an evolution of the original QSFP transceivers released in 2006 and can handle a higher data transfer rate.
In this article, we look at what QSFP+ is and how it can be utilised within your network architecture.
What is QSFP+?
QSFP+ stands for Quad Small Form Factor Pluggable Plus. This may seem a bit of a mouthful, but each part of its name refers to a specific feature within the device. “Quad” refers to the fact that it uses four independent channels to either transmit or receive data through the transceiver. “Form Factor” relates to its size, which in this case is small and compact. “Pluggable” means it is designed to be hot swappable, so can be added or removed from a network setup without network downtime being needed. “Plus” refers to the fact that it can handle higher rates of data transmission than regular QSFP.
How does QSFP+ work?
A QSFP+ takes four separate lanes of information, also called channels, and sends them over a single fibre optic cable as one signal. It does this by utilising a technology called Coarse Wave Division Multiplexing (CWDM).
CWDM uses a wider wavelength range with wider channel spacing. Typically, CWDM supports wavelengths from 1270 nm to 1610 nm, separated by intervals of 20 nm. This means it is only suitable for sending a signal over a shorter distance, usually up to 80km. CWDM differs from DWDM (Dense Wavelength Division Multiplexing), in that the latter is capable of using a narrower wavelength, meaning it can send signals over a longer distance without risking significant signal degradation.
Each electrical input into the QSFP+ is turned into an optical signal at a different optical wavelength. These four separate signal wavelengths are then combined into one optical signal and sent through the fibre optic cable in a process called multiplexing. At the other end of the fibre cable, a second QSFP+ then reverses this process (demultiplexing) and turns the one optical signal back into four separate electrical channels which are then sent to the relevant piece of networking equipment.
QSFP+ transceivers usually consist of several key components which allow them to operate. Here we provide a quick overview of each and how it allows the transceiver to function.
- Transmitter
The transmitter section of a QSFP+ transceiver consists of laser diodes or LEDs responsible for converting electrical signals into optical signals. The transmitter emits light at specific wavelengths, which are then transmitted over the optical fibre.
- Receiver
The receiver section of the QSFP+ transceiver receives the incoming optical signals from the fibre and converts them back into electrical signals. It typically includes a photodiode or avalanche photodiode (APD) that detects the incoming light and generates electrical signals proportional to the received optical power.
- Electrical interfaces
QSFP+ transceivers also have electrical interfaces to connect with the host system or network equipment. These interfaces follow industry-standard electrical signalling protocols, such as 10 Gigabit Ethernet, 40 Gigabit Ethernet, or InfiniBand. The electrical interfaces enable the exchange of electrical signals between the transceiver and the specific piece of networking equipment it is connected to.
- Optical interfaces
QSFP+ transceivers use optical interfaces to transmit and receive data signals. These interfaces are designed to connect with optical fibres and utilise laser diodes or light-emitting diodes (LEDs) to convert electrical signals into optical signals for transmission and vice versa for reception.
- The housing
A QSFP+ transceiver typically comes in a compact module with a standardised pluggable form factor, allowing for easy installation and replacement. QSFP+ transceivers are designed to be a hot-pluggable module, meaning they can be inserted or removed from the host device without powering off the system. This is critical when deployed in a data centre where even the smallest amount of network downtime can be costly.
- Control, monitoring & management interface
Many QSFP+ transceivers often incorporate control and monitoring functionality which allows the network operator to monitor the performance of the transceiver in real time including the temperature, voltage, and received optical power. Having the ability to monitor the performance of the transceiver means network operators can ensure it is performing at its peak.
Some QSFP+ transceivers may also feature a management interface, such as an I2C (Inter-Integrated Circuit) bus. This interface allows for direct communication between the transceiver and the host device, allowing the network operator to perform advanced configuration, monitoring, and control of the transceiver.
You can read our full guide on how a fibre optical transceiver works here.
What is QSFP+ used for?
QSFP+ is a type of fibre optical transceiver. It is used to convert electrical signals from a network device into an optical signal via a laser or diode, which is then transmitted through a fibre optic cable. Fibre optic transceivers are crucial in modern telecommunications as they allow for faster rates of data transmission when compared to traditional methods such as copper cables.
In the case of QSFP+, they are capable of supporting 40G Ethernet by utilising four lanes of 10G Ethernet fibre; this differs from QSFP which only supports four lanes of 1G Ethernet. The extra capacity of a QSFP+ over a QSFP is an important consideration when choosing which transceiver is most suitable for your business.
One of the key benefits of a QSFP+ is its data handling capacity compared to its relatively small size. A QSFP+ is usually no more than the size of a standard AA battery but can still support high rates of data transmission by using four separate channels. These channels can be used to send or receive data independently to each other, making them very efficient. This makes it ideal to use where space is a key consideration when deciding on your network’s setup.
Another benefit to this type of transceiver comes from its ability to be ‘hot-swapped’. This means the unit can be removed from a piece of network equipment and replaced with another, without the need for the network to be taken offline. This is key in a data centre, where long periods of downtime can be costly to the business using it.
QSFP+ FAQs
What is the difference between QSFP+ and QSFP28?
QSFP28 is another type of optical transceiver. However, it differs from QSFP+ in that is able to support a higher level of data transfer. Where a QSFP+ supports 4 x 10GB, QSFP28 supports 4 x 25GB. The 28 in its name relates to the fact that it can support a 28 GB transfer rate. Technically a QSFP28 is backwards compatible with a standard QSFP+ network configuration, however, it will not be able to use its full data transfer rates.
Which manufacturers make QSFP+ optical transceivers?
Most large telecom manufacturers make their own versions of QSFP+ transceivers, including Dell, Juniper, Cisco and Alcatel-Lucent. TXO stocks a full range of QSFP+ optical transceivers from many different manufacturers, including OEM compatibles, so contact us today to find out how we can help with your existing network setup.
