Jul 07


Nowadays, the demand for high bandwidth increases and footprints for data center expands dramatically, which makes the migration from 10G to 40G much more necessary than ever before. Under this condition, many enterprises are ongoing or imminent to upgrade their data center network infrastructures. To better cater for our users, two transceivers 40G UNIV and 40G SWDM4 QSFP using SWDM (Short Wavelength Division Multiplexing) technology are compared in the following text, which intends to offer a cost effective transceiver solution for 10G to 40G migration applications. As parallel multimode MPO fiber cabling is much more expensive than Duplex-LC fiber cabling, Duplex-LC fiber patch cords will be used in these two SWDM applications, as a cost saving cabling method.

40G Direct Port-to-Port Connection

QSFP 40G UNIV Transceiver for SWDM Application

QSFP 40G UNIV is a kind of pluggable optical transceiver that fitted with Duplex-LC connector and can work with both single-mode and multimode fiber patch cable, originally released by Arista. Hence, it is also referred to as 40G SMF&MMF transceiver or 40G QSFP universal transceiver. When working with singlemode fiber, the Arista QSFP 40G UNIV can support 40G connection with a reach of 500m; and over OM3/OM4, the transmission distance can be up to 150m. Furthermore, the Arista QSFP 40G UNIV is designed with four 10G channels for transmitting and receiving four individual 10G signals through a single Duplex-LC fiber patch cord, for achieving a total 40G connection, as shown in the following figure.

Arista QSFP 40G UNIV

How does the Arista QSFP 40G UNIV work for 40G connection? The answer is SWDM technology. With the help of SWDM, Arista QSFP 40G UNIV will multiplex four wavelengths 1270nm, 1290nm, 1310nm and 1330nm to transmit four 10G signals over the single Duplex-LC fiber patch cord. And when the aggregate 40G signal passes through the receiver end, it will be demultiplexed into four individual 10G signals again. As a result, an aggregate 40G signal can be transmitted through a single Duplex-LC fiber patch cord. In short, Arista 40G universal transceiver is a very good choice for 40G migration which can work with LC-duplex single-mode or multimode fiber, instead of high-cost parallel multimode MPO fiber cabling.

QSFP 40G SWDM4 Transceiver for SWDM Application

QSFP 40G SWDM4 is an updated optical transceiver that basically works with Duplex-LC fiber patch cord for short 40G fiber link. It has the same working principle that uses SWDM technology as the QSFP 40G UNIV one, but can perform better. How does it do this? Unlike QSFP 40G UNIV working with both single-mode and multimode fiber, the QSFP 40G SWDM4 is designed to work with multimode fiber, which can transmit a multiplexed 40G signal over wide band OM5 at lengths up to 440m. It can also work in multimode fiber OM3 and OM4 with a reach of 240m and 350m, separately. What’s more, the power dissipation of QSFP 40G SWDM4 can be as low as 1.5W* since SWDM technology can match 4x WDM optical architecture with 4x electrical interface.

Similar to the QSFP 40G UNIV transceiver, four different wavelengths, 850nm, 880nm, 910nm and 940nm are used in the QSFP 40G SWDM4 transceiver. To transmit a total 40G signal, these four wavelengths will be multiplexed to carry four individual 10G signals, be transmitted through the Duplex-LC multimode fiber patch cord and finally demultiplexed. To better understand the principle of QSFP 40G SWDM4 transceiver, you can learn the above figure that illustrates how does the QSFP 40G SWDM4 work for a short distance 40G fiber link.

40G SWDM4 Transceivers

QSFP-40G-UNIV vs QSFP-40G-SWDM4, Which One is Better?

After discussion, we can learn that both QSFP 40G UNIV and QSFP 40G SWDM4 transceivers enable network operators to grow the capacity of their networks without laying new fiber cabling. In view of the transmission distance, QSFP 40G SWDM4 transceiver working with OM5 supports a longer 40G fiber link than QSFP 40G UNIV with OM3/OM4, but a shorter 40G fiber link than QSFP 40G UNIV with single mode fiber cable. When taking fiber cabling infrastructure cost into consideration, OM5 cabling costs about 50% more than OM4 and singlemode fiber is also very expensive. Then which one should be selected? Just depending on your network needs, such as the fiber link distance, the budget, etc. To better know the differences between QSFP 40G UNIV and QSFP 40G SWDM4 transceivers, here offers a table that shows their detailed parameters.


Mar 22


Due to the ever-increasing requirement for higher speed transmission, 40G Ethernet is introduced to networking world, and it will gradually dominates the market. Many vendors have released different kinds of devices to support 40GbE, among which 40G QSFP+ module is the most popular and available for short distance or long distance data transmission. There are two variants short distance QSFP+ modules: QSFP-40G-SR4, and QSFP-40G-UNIV, what are the differences among these two types? This passage will tell you and give more information.

Differences in Interfaces and Transmission Media

Commonly, for QSFP+ modules, there are mainly two connector interfaces: MPO/MTP and duplex LC(Note: LC interfaced QSFP+ uses serial transmission, while MPO/MTP interfaced QSFP+ uses parallel transmission. In serial transmission, bits are sent simultaneously on different channels within the same cable, and in parallel transmission, bits are sent sequentially on the same channel). QSFP-40G-SR4 uses MPO/MTP to achieve data transmission over multimode fiber. However, in order to avoid wasting cost and deployment time when installing in different cabling structure, duplex LC interfaced QSFP-40G-UNIV is designed to be used in both single-mode and multimode links without adding any hardware or software.

different interface between QSFP-40G-SR4 and QSFP-40G-UNIV

Differences in Working Principle

For MPO/MTP interfaced 40GBase-SR4, it offers 4 independent full-duplex transmit and receive channels, each capable of running up to 10G data rates per channel, achieving the total 40G data rates. These modules are often used with 12-fiber MTP trunk cable, four transmitting and four receiving, leaving the middle four unused. For duplex LC interfaced 40GBase-UNIV, it also uses four transmitters and four receivers but has built in optical multiplexing and de-multiplexing, which results in a duplex connector and hence operates over the same duplex fiber infrastructure as 10GBASE-SR.

different working principle of QSFP-40G-SR4 and QSFP-40G-UNIV

Differences in Transmission Distance

40GBase-SR4 module can support link lengths of 100 meters and 150 meters, respectively, on laser-optimized mutimode fibers, and it can also be used in a 4x10G mode interoperability with 10GBase-SR interfaces up to 100 and 150 meters on OM3 and OM4 fibers, respectively. 40GBase-UNIV can support the same transmission distance over OM3 and OM4 fibers, but it can also achieve link lengths of up to 500 meters over single-mode fiber.

Differences in Cost Consumption

40GBase-UNIV is much more expensive than 40GBase-SR4. Take FS.COM for example, 40GBase-UNIV is $340, while 40GBase-SR4 is $55. Besides the price of the unit itself, we should also take the whole deployment cost consumption into consideration. Migrating from 10G to 40G is inevitable. The existing 10G network uses two fibers for dual transmission. But most 40G network uses 12-fiber MTP based fiber optic cable for dual-way transmission over multimode fibers, which means if we use 40GBase-SR4 with MTP port for 10G to 40G migration, more optical fibers will be added and the cabling infrastructure will be changed. However, with 40GBase-UNIV module, it can support the same or longer transmission distance as the 40GBase-SR4 does, but it uses two strands of dual-way transmission like most 10G network, which will keep the existing 10G network when upgrade to 40G, greatly saving cost and time.

10G to 40G migration with QSFP-40G-SR4 and QSFP-40G-UNIV


We have introduced QSFP-40G-SR4 and QSFP-40G-UNIV modules for short distances transmission. These two module types have different features. Choosing which one totally depends on your practical applications and budgets. FS.COM has plenty of QSFP-40G-SR4 and QSFP-40G-UNIV optics in stock. For more information, please check FS.COM.

Feb 08

Interfaces for 40 GbE Architecture in Data Centers II

In the previous post “Interfaces for 40 GbE Architecture in Data Centers I”, we generally learned about the Chip-to-chip port side interface in the 40 Gigabit Ethernet architecture. And in this post, we will continue to learn the interfaces used for 40 Gigabit Ethernet. This article will focuses on the Chip-to-module direct attach interface.

Chip-to-module direct attach interface

A chip-to-module interface consists of a short PCB trace and a module connector between a port side IC and a module that is without retiming capability.

To increase the port densities to achieve the higher required bandwidth in chassis, the signal conditioning function was moved from inside of a 10 Gigabit pluggable module, such as XFI, to the port side interfaces. As a result, a new high-speed 10 GE serial electrical interface called SerDes Framer Interface (SFI) was defined by SFF MSA. SFI is applied for an interface between a host ASIC and the small form-factor pluggable module, SFP+ (the follwing picture shows the connection methods).

connection methods of chip to module

SFI is defined for both limiting and linear mode modules. In the limiting mode, SFI supports PHY connections to the limiting SFP+ optical transceivers, such as 10GBASE-SR optics(MMF 300m), 10GBASE-LR optics(SMF 10km), and 10GBASE-ER optics(SMF 40km). In the linear SPI interface, stronger signal conditioning capabilities are required to compensate for electrical dispersion. The linear SPI interface can be used with 10GBASE-LRM optics, and also the passive Direct Attached Copper (DAC) in the length from 1m to 7m, such as QSFP-H40G-CU5M DAC and EX-QSFP-40GE-DAC-50CM DAC.

To improve the port side densities in a chassis, the new XLPPI (40 Gbps Parallel Physical Interface) electrical specification was defined by IEEE 802.3. Another reason for the development of XLPPI is to address the incompatibility between the XLAUI and the QSFP+ module. Therefore, XLPPI is an interface with high port-density, supporting a direct connection to a Quad Small Form Factor Pluggable (QSFP or QSFP+) module (e.g. Brocade QSFP+ and Finisar QSFP+) without the necessity of a re-timer function.

Compared with XLAUI interfaces, XLPPI Interface is defined in 802.3ba Annex 86a as the interface between the PMA and PMD functions (where as the XLAUI dissects the PMA). The XLPPI is derived from the SFI interface and places higher signal integrity requirements on the host PMA than the XFI based XLAUI.

XLPPI is the electrical specification to both passive copper based 40GBASE-CR4 QSFP+ module and the optical modules such as the short reach 40GBASE-SR4 optical transceiver and 40GBASE-LR4 optical transceiver. Therefore, currently QSFP+ modules with XLPPI interfaces support 40GBase-CR4 (both passive and active) cables and 40GBase-SR4 (either AOC or using the MPO/MTP®connector) cables.

Jan 25

40G Transceivers: CFP, QSFP and CXP

In fiber optic communication, 40GbE transceivers are being developed along several standard form factors, such as CFP (C form-factor pluggable) transceiver, QSFP/QSFP+ (quad small-form-factor pluggable) transceiver and CXP optical transceiver. This article will introduce the three types of optical transceivers to further your understanding of 40G optics.

CFP Transceiver

CFP, short for C form-factor pluggable, is compliant with multi-source agreement (MSA) to produce a common form-factor for the transmission of high-speed digital signals. The C in the acronym “CFP” stands for the Latin letter C, which refers to the number 100 (centum), since the standard was primarily designed for 100 Gigabit Ethernet systems. In fact, CFP also supports the 40GbE. When talking about CFP, we always define it as multipurpose CFP.


The CFP form factor, defined in the MSA, supports both singlemode and multimode fiber and a variety of data rates, protocols, and link lengths, including all the physical media-dependent (PMD) interfaces contained in the IEEE 802.3ba Task Force. At 40GbE, target optical interfaces include the 40GBase-SR4 for 100 m and the 40GBase-LR4 for 10 km. There are three PMDs for 100 GbE: 100GBase-SR10 for 100 m, 100GBase-LR4 for 10 km, and 100GBase-ER4 for 40 km.

QSFP/QSFP+ Transceiver

QSFP/QSFP+ transceiver (Quad Small Form-factor Pluggable Plus) is a wildly used transceiver interfaces in data communications, connecting a network device motherboard (e.g. a switch, router, media converter and the like) with a fiber optic cable. It is a industry format that is jointly developed and supported by many network component vendors, such as Dell QSFP+, Juniper QSFP+, Mellanox QSFP+ and HP QSFP+. Additionally, QSFP supports both copper and optical cabling solutions.

Compared with the CXP, the QSFP (quad small-form-factor pluggable) is similar in size (shown as the following picture). It provides four transmitting and four receiving lanes to support 40GbE applications for multimode fiber and copper today and may serve single-mode in the future. Another future role for the QSFP may be to serve 100GE when lane rates increase to 25Gb/s.


CXP Transceiver

“C” in the acronym CXP represents for 12 in hex, and the Roman number “X” means that each channel has a transmission rate of 10 Gbps. “P” refers to pluggable that supports the hot swap. Thus, CXP is a hot-pluggable transceiver with data rate up to 12×10 Gbps.

CXP is developed for the clustering and high-speed computing markets, so we also call it high-density CXP. the CFP is able to work with multimode fiber for short-reach applications, but it is not really optimized in size for the multimode fiber market, most notably because the multimode fiber market requires high faceplate density. The CXP was created to satisfy the high-density requirements of the data center. It is featured with the parallel interconnections for 12x QDR InfiniBand (120 Gbps), 100 GbE, and proprietary links between systems collocated in the same facility.

As stated above, these 40G optics have been very popular in the market, and they are able to keep the momentum in the future for 100G transmission.

Jul 22

QSFP Transceiver – Economic 40G Transceiver Solution

The optical communication industry has been enjoying great growth for many years. Now the mobile and virtualized workloads, cloud applications, big data, heterogeneous devices are promoting the development of this industry further more. The demands for faster connection speed have been more and more significant. Many operators and data centers have been upgrading their networks, during which an optical component—fiber optic transceiver plays an important role.

Various fiber optic transceivers have been invented. However, there are several types can be regarded as the milestone of the development of fiber optic transceivers. Since 2002, SFP transceivers has replaced XFP transceivers gradually and has become the mainstream part of the 10GB/s market. Now the data rate of fiber optic networks is kept growing. The footstep of transceiver’s developing won’t stop here. This industry is moving to the 40GB/s time. The new kind of fiber optic transceivers has been invented—40G optical transceiver.

The most common optical transceiver that supports a data rate of 40Gb/s is QSFP transceiver. QSFP (quad small form-factor pluggable) transceiver is a hot-pluggable interface provides four channels of data in one pluggable interface. Each channel is capable of transferring data at 10Gb/s. Thus, a QSFP transceiver with four-high-speed-channel can support data rates up to 40Gb/s and is widely used in computing and telecommunication applications.

qsfp-transceiverThe QSFP transceiver designed to enable extremely high-density applications with stacked and ganged configurations has excellent features:

  • High density & Space saving—The QSFP module replaces four standard SFP modules in a space that is only 30 percent larger than a single SFP. However, QSFP transceiver has 4 channels in one interface which can provide 3 to 4 times density of SFP.
  • High data rate—the QSFP can support Ethernet, fiber channel, and SDH/SONET with data rates up to 10 Gb/s per channel, 40 Gb/s in total.
  • Economics—The QSFP transceiver demonstrates potential for aggregated higher volumes and can improve the economic benefits effectively.
  • Switches, Routers, and host bus adapters (HBA’s)
  • Enterprise storage
  • High density, high speed I/O (input/output)
  • Multiple channel interconnects, etc.
Fiberstore Solutions

QSFP currently is the most common optical transceivers that are applied for 40Gb/s use. Fiberstore provides a wide rage of 40Gbase QSFP/QSFP+ transceivers, including 40Gbase-PLRL4 QSFP+ transceiver and 40Gbase-LR4 QSFP+ transceiver which can be shipped in 12 hours. For more information please visit Fiberstore.