In-Depth Study of CWDM Transceivers

It is easy to learn that CWDM stands for Coarse Wavelength Division Multiplexing, which belongs to one of WDM technologies. With the fast development and gradual maturity of WDM technologies, CWDM technology becomes popularly used in recent years that allows for expanding network capacity without more fibers and supporting less expensive and power consuming system. For all these advantages, CWDM technology is applied in many optical equipment. One of the most popular equipment that uses this technology is CWDM optical transceiver, which will be introduced in the following text.

CWDM Transceiver

CWDM transceiver is a kind of optical module typically working with CWDM technology, which is designed for connecting the existing network equipment with CWDM multiplexers/demultiplexers (Mux/Demux). As for its working principle, it is able to combine optical signals with different wavelengths in the multiplexers side and transmit the integrated signal through a single fiber, while splitting the integrated signal into several signals with different wavelengths in the demultiplexers side. And there are eighteen channels available in CWDM transceiver for transmitting signals with different wavelengths from 1270 nm to 1610 nm, such as 1270 nm, 1290 nm, 1310 nm, 1330 nm, etc.

At present, CWDM transceiver can be simply divided into four types, CWDM SFP, CWDM SFP+, CWDM XFP and CWDM X2, both of which will be studied in details. Besides, to better know CWDM transceivers, here offers the figure for the appearance of the four CWDM transceivers for your reference.

CWDM SFP

CWDM SFP is a kind of hot-pluggable optical module, which is SFP MSA (Multi Sourcing Agreement) and IEEE 802.3 & ROHS compliant. Compared to other CWDM transceivers, CWDM SFP is the most commonly used module that connects LC duplex single-mode patch cord to support 1G, 2G and 4G Ethernet network at lengths up to 200 km. In its working process, it enables the network capacity to be increased by transmitting multiple data through a single fiber, with the function of combining optical signals with different wavelength into an integrated signal.

As for the application, CWDM SFP can support the CWDM passive optical system combing CWDM OADM (optical add/drop multiplexer). If you use CWDM SFP to work with transponders and media converters, you will find that the two optical components convert the existing equipment with standard wavelengths or copper ports to CWDM wavelengths in a very convenient way.

CWDM SFP+

CWDM SFP+ is an upgraded version of CWDM SFP that offers a simple way to make 10G network connection. It has the ability to work with up to eight channels for transmitting 10G signals at the wavelengths including 1470 nm, 1490 nm, 1510 nm, 1530 nm, 1550 nm, 1570 nm, 1590nm, and 1610 nm, through single-mode fiber strands. And it can be used in parallel with other SFP+ devices on the same platform.

In contrast to CWDM SFP, it is much more expensive. However, taking 10G Ethernet applications into consideration, CWDM SFP+ is really a cost-effective solution in campus, data center and metropolitan area access networks. After all, it allows for increasing the bandwidth of an existing 10G Ethernet optical infrastructure without adding new fiber strands.

CWDM XFP

Just like CWDM SFP+, CWDM XFP is also used for 10G Ethernet applications with Z-direction design, which complies with CWDM XFP MSA. What’s about the cost? It is also nearly the same as that of CWDM SFP+. Meanwhile, it can transmit 10G signals at the distance up to 100 km, which depends on the wavelengths, fiber types and the CWDM Mux/DeMux insertion loss. Besides, it is mainly used in Storage, IP network and LAN applications, working with the wavelengths from 1270 nm to 1610 nm.

CWDM X2

In comparison with the previous three CWDM transceivers, CWDM X2 is the most expensive one which is suitable for CWDM optical data communications like 10G Ethernet and 10G Fibre Channel applications. Similar to CWDM XFP, it also works with the wavelengths from 1270 nm to 1610 nm, supporting 10G transmission at lengths up to 80 km over SC duplex single-mode fiber cable.

Conclusion

CWDM transceivers can greatly expand the network capacity without additional fibers by connecting the existing network equipment with CWDM multiplexers/demultiplexers (Mux/Demux). It is really a cost effective solution for higher capacity that allows for a highly flexible and available multi-service network. As for the four kinds of CWDM transceivers mentioned above, you can choose the proper one according to their features and your existing network need.

Selecting the Right 40G QSFP+ Transceivers and Cables

It is well known that telecommunication equipment experts have designed and developed a variety of fiber optical products to meet the increasing requirements of our network. As one of the most important components among these fiber optical products, fiber optic transceiver has caused more and more value that has been diversified to achieve higher and higher transmission speed and smaller and smaller size, such as, GBIC, SFP, XFP, SFP+, QSFP+, etc. In this post, it will give a detailed selection guide to QSFP+ transceivers and their cabling options, both of which are very popular and commonly used in building 40G Ethernet network.

Commonly Used 40G QSFP+ Transceivers

QSFP+ transceiver is also known as Quad Small Form-factor Pluggable transceiver, which is designed for 40G Ethernet network. Generally, it has four channels of data in one pluggable interface and each channel has the ability to transmit the data at 10Gb/s rate. Thereby, it can support 40G Ethernet network. The following will introduce three commonly used QSFP+ transceivers, 40GBASE-SR4, 40GBASE-SR-BiDi and 40GBASE-ER4, helping you choose the most suitable one for your network.

40GBASE-SR4 Transceiver

40GBASE-SR4 transceiver can support 40G Ethernet network by transmission through muldi-mode fiber (MMF), which is able to transmit signals at lengths up to 100 meters through laser-optimized OM3 and 150 meters through OM4. The high-bandwidth 40G optical network is set up through 12-fiber parallel fiber that terminated with MPO/MTP multi-fiber female connectors, occupying 4 fibers for sending signals, 4 fibers for receiving signals and 4 fibers wasted. In addition, it can also be applied in a 4x10G mode for interoperability with 10GBASE-SR interfaces, with no change in transmission distance.

40GBASE-SR-BiDi Transceiver

40GBASE-SR-BiDi is a pluggable optical transceiver with a duplex LC connector interface for short distance data communication and interconnect applications, also working with MMF. Each QSFP 40GBASE-SR-BiDi transceiver is composed of two 20G transmitting and receiving channels in the 832-918nm wavelength range, which enables an aggregated 40G link over a two-strand MMF connection. Compared to 40GBASE-SR4 transceiver, this kind of transceivers only requires a duplex LC patch cord to accomplish 40G transmission at lengths up to 100 meters over OM3 and 150 meters over OM4 that works in a much more straightforward transmission mode. In short, 40GBASE-SR-BiDi transceiver gives the users a big convenience to build their 40G Ethernet network.

40GBASE-ER4 Transceiver

Clearly different from the previous transceivers, 40GBASE-ER4 works over single mode fiber (SMF) to finish 40G communication, supporting the link at lengths up to 40km with duplex LC connectors. There are four kinds of wavelengths in the 1310nm range used to transmit signals, which will be multiplexed and demultiplexed in the transmission process. If you want to build your 40 Ethernet network for long distance transmission, this kind of transceivers must be a good choice.

Commonly Used 40G QSFP+ Cabling Options

In general, there are three commonly used 40G QSFP+ cabling options, QSFP to QSFP copper direct attach cables (DACs), QSFP to QSFP active optical cables (AOCs), QSFP to four SFP+ breakout cables as shown in the following figure. To better understand the features of these cabling options, you can take the listed information as reference.

As for QSFP to QSFP Copper DACs and QSFP to QSFP AOCs, both of them are developed for short distance transmission by providing a flexible solution for connection within racks and across adjacent racks. In contrast to DACs, AOCs are much thinner and lighter that facilitates the cabling. Since AOCs enable efficient system airflow and have no EMI issues, there is no doubt that AOCs have a higher performance than DACs when designing 40 Ethernet network.

As for QSFP to four SFP+ breakout cables, they are available in two types: QSFP to four SFP+ copper breakout cables and QSFP to four SFP+ active optical breakout cables, which can be in 1m, 2m, 3m, 5m, 7m and 10m. By offering more space for data centers with low cost, this kind of 40G QSFP+ cabling option becomes a highly cost-effective interconnect solution to set up 40 Ethernet network.

Conclusion

From this post, we can conclude that 40GBASE-SR4 and 40GBASE-SR-BiDi transceiver are commonly used in short distance 40G transmission, while 40GBASE-ER4 can support 40G transmission with long distance. As for the 40G QSFP+ cabling options, you can choose the most suitable one to match your network. Hope the information in this post would be helpful for your 40G QSFP+ optics selection.