A Closer Look at 40G QSFP+ SR4 Transceiver

As 40G network has been widely applied in today’s data center cabling system, 40G QSFP+ transceivers gain great popularity among data center managers. And for short data transmission distance, 40G QSFP+ SR4 transceiver is preferred. This article is going to focus on 40G QSFP+ SR4 transceiver and share several cabling solutions for 40G QSFP+ SR4 with you.

Overview of 40G QSFP+ SR4 Transceiver

40G QSFP+ SR4 transceiver is a parallel fiber optic transceiver which means it uses four fibers for transmitting and four fibers for receiving at the same time. Designed with MTP/MPO interface, 40G QSFP+ SR4 transceiver is used together with multimode fiber, such as OM3 and OM4. Working on wavelength of 850 nm, 40G QSFP+ SR4 transceiver can support 40G fiber optic transmission with the link length up to 100 meters over OM3 fiber and 150 meters over OM4 fiber. For application, 40G QSFP+ SR4 transceiver can be used for 10G to 40G and 40G to 40G connections. Here is a figure of 40G QSFP+ SR4 transceiver for you.

40G QSFP+ SR4 transceiver

10G to 40G Connection

Since 40G QSFP+ SR4 transceiver uses four independent full-duplex transmit and receiver channels, the 40G optical signal can be split into four 10G optic signals. Therefore, we can increase the fiber count at the 10G distribution end to realize 10G to 40G connection. As the following figure shows, we can use 12f MPO trunk cable and fiber enclosure. Four 10G SFP+ SR transceivers are inserted into 10G ports on one side, while one 40G QSFP+ SR4 transceiver is inserted into 40G port on the other side. Then the four 10G SFP+ SR transceivers are connected with four duplex LC patch cables which are plugged into LC ports on the front side of MPO fiber cassette inside the fiber enclosure, and the 40G QSFP+ SR4 transceiver is connected with 12f MPO trunk cable which is plugged into MTP/MPO port on the rear of MPO fiber cassette. Finally, the whole optical link is completed.

40G QSFP+ SR4 transceiver for 10G to 40G connectionA

We can also use MPO to LC fanout and MTP fiber patch enclosure which includes MTP fiber adapter panels. This cabling solution is similar to the previous one, but the difference is that the four 10G SFP+ SR transceivers are connected with MPO to LC fanout which is plugged into MTP/MPO port on the MTP fiber patch enclosure. The scenario is shown in the following figure.

40G QSFP+ SR4 transceiver for 10G to 40G connectionB

40G to 40G Connection

The following figure shows the simplest scenario for 40G to 40G connection. Two 40G QSFP+ SR4 transceivers are separately inserted into two 40G switches. Then the two 40G QSFP+ SR4 transceivers are connected by 12f MPO trunk cable.

40G QSFP+ SR4 transceiver for 40G to 40G connectionA

We can also use MTP fiber patch enclosure to achieve better cable management and higher density cabling. The scenario is shown in the following figure. With the use of MTP fiber enclosure, cable management for 40G to 40G connection could be easier. A 48-port 1U rack mount MTP fiber patch enclosure includes up to four 12-port MTP fiber adapter panels with MPO MTP fiber optical adapters on it, here is a figure for you.

40G QSFP+ SR4 transceiver for 40G to 40G connectionB

Conclusion

Designed with parallel transmission mode, 40G QSFP+ SR4 transceiver has a wide range of cabling applications with great flexibility. The cabling solutions mentioned above are just several commonly used ones. As for detailed cabling solutions for 40QSFP+ SR4 transceiver, it is suggested to depend on the practical applications and cabling environments. I hope after reading this article, you can learn more about 40G QSFP+ SR4 transceiver.

Difference Between 40G QSFP+ Transceiver with LC Interface and MTP/MPO Interface

Data transmission with higher density and bandwidth has become the trend under present networking environment. With 40 Gigabit Ethernet commonly deployed in most data centers, various network devices designed for 40 Gigabit Ethernet (GbE) link are available on the market. Among them, 40G QSFP+ transceivers play an important role in driving the bandwidth to a mounting point. There are mainly two interfaces adopted by 40G QSFP+ transceivers—MTP/MPO and LC. What is the difference between these two interface types? This article will have an analysis of the 40G QSFP+ transceivers with LC interface and 40G QSFP+ transceivers with MTP/MPO interface.

40G QSFP+ transceiver with MTP and LC interface

40G QSFP+ Transceivers With LC Interface

From the figure below, we can easily understand the working principle of 40G QSFP+ transceivers with LC interface. In the transmit side, 4 channels of 10G serial data streams at different wavelengths are passed to laser drivers. The laser drivers control directly modulated lasers (DML) with wavelengths. Then the output of the four DMLs are optically multiplexed to a SMF through an industry-standard LC connector, combining as 40G optical signal. In the receive side, the 40G optical signal is demultiplexed into four individual 10G optical data streams at different wavelength. And each wavelength light is collected by a discrete photo diode and amplified by a TIA, and then outputted as electric data. In this process, a 4-wavelength CWDM multiplexer and demultiplexer is used over a pair of single-mode fibers. For transmission distance of this type of 40G QSFP+ transceiver, take 40G LR4 QSFP+ transceiver as an example, it can support an optical link length up to 10 kilometers over the single mode fiber.

40G QSFP+ transceiver LC interface working principle

40G QSFP+ Transceivers With MTP/MPO Interface

We can easily understand the working principle of 40G QSFP+ transceiver with MTP/MPO interface from the figure below. In the transmit side, the transmitter converts parallel electrical input signals into parallel optical signals through the use of a laser array. Then the parallel optical signals are transmitted parallelly through the multimode fiber ribbon terminated with MPO/MTP fiber optic connector. In the receive side, the receiver converts parallel optical input signals via a photo detector array into parallel electrical output signals. Generally, 40G QSFP+ transceivers with MTP/MPO interface are utilized for short distance transmission over multimode fiber (MMF), like 40G SR4 QSFP+ transceiver, it can support a link length up to 100 meters on OM3 cable and 150 meters on OM4 cable.

40G QSFP+ transceiver with MTP MPO interface working principle

Note: there are also some 40G QSFP+ transceivers with MTP/MPO interface supporting long distance transmission over SMF. For example, 40G LR4 PSM QSFP+ transceiver, a parallel single-mode optical transceiver with an MTP/MPO fiber ribbon connector, it offers four independent transmit and receive channels, each capable of 10G operation for an aggregate data rate of 40G over SMF. That is to say, eight single-mode fibers are used to achieve parallel transmission, with transmission distance up to 10 kilometers. From the perspective of cost, this kind of 40G QSFP+ transceivers cost more than 40G QSFP+ transceivers with LC interface. Besides, in the data center fiber infrastructure, MTP patch panel has to be used to accommodate MTP cables, which would cost more than LC connectors and regular SMF cables.

4x10G Connectivity

For the 40G QSFP+ transceivers with LC interface, they cannot be split into 4x10G as they use 4 wavelengths on a pair of single-mode fibers and do not lend themselves to “splitting” into 4 pairs without substantial complexity to split out the wavelengths. For the 40G QSFP+ transceivers with MTP/MPO interface, they can be used in 4x10G connectivity via an external 12-fiber parallel to 2-fiber duplex breakout cable, which connects the 40G module to four 10G optical interfaces.

Conclusion

Generally speaking, the 40G QSFP+ transceivers with LC interface are used for long distance transmission over single-mode fiber (SMF), and 40G QSFP+ transceivers with MTP/MPO interface are utilized for short distance transmission over multimode fiber (MMF). However, for some 40G QSFP+ transceivers with MTP/MPO interface, such as 40GBASE-LR4 PSM QSFP+ transceiver, it can support long distance transmission over SMF. Besides the examples discussed above, there are some other types of 40G QSFP+ transceivers provided by FS.COM, such as 40GBASE-CSR4 QSFP+, 40GBASE-PLR4 QSFP+, 40GBASE-ER4 QSFP+ and so on. If you want to know more details, please visit our site.