Migrate to 40G Network Cost-effectively with BiDi QSFP+ Transceiver

As data center consolidation, server virtualization, and new applications require higher data transmission speed, it is imperative to migrate from 10G network to 40G network. However, to support the 40G connectivity, data center managers have to upgrade the existing 10G cabling infrastructure, which could be too expensive or disruptive to allow data center to quickly adapt and migrate to the 40G technology. Therefore, innovative 40G BiDi QSFP+ transceiver, which allows reuse of existing 10G fiber infrastructure for 40G connections, is designed to solve this problem. However, what is BiDi QSFP+? How does it work? And what are the advantages of BiDi QSFP+ over traditional QSFP+? This post will answer these questions one by one.

What Is BiDi QSFP+ Transceiver?

BiDi QSFP+ transceiver is a latest product used for 40G short-reach data communication and interconnect applications. Compliant with the QSFP MSA specification, it is terminated with a duplex LC connector interface to transmit data over laser-optimized OM3 and OM4 multimode fiber cables for the length of up to 100 m and 150 m respectively, that is the same as the traditional QSFP-40G-SR4 (like Arista QSFP-40G-SR4). This 40G transceiver has two 20G channels, and each channel transmits and receives two wavelengths over a single multimode fiber strand. The following image shows a Cisco 40GBase-SR BiDi QSFP+ transceiver.

How Does BiDi QSFP+ Work with Existing 10G Optics?

As we all know, 40GBase-SR4 QSFP transceiver uses four 10G lanes to support 40G through a 12-fiber MTP-MPO interface, with four for transmitting and receiving and the rest are unused. However, a BiDi QSFP+ transceiver can accomplish both the transmitting and receiving via a duplex LC patch cable. So it can be deployed in the existing 10G cabling infrastructure, which also uses duplex transmission mode.

Inside this module, four channels each of 10G signal transmission and reception are converted to two bidirectional channels of 20G signals over two different wavelengths (usually 850 nm and 900 nm) respectively (shown in the following picture). The signal is sent to the target device via 850 nm, then the signal from the target device is sent via 850 nm on the other fiber. This principle also works for the signals on 900 nm. This is why BiDi QSFP+ can achieve the migration from 10G to 40G without changing the existing infrastructure. It is more straightforward than the traditional 40G connections for short distance.

Economic Advantages of BiDi QSFP+ Transceiver

As we have mentioned above, a BiDi QSFP+ transceiver can give you 40G over your existing 10G cable plant, which means that you can connect your top-of-rack switches using the same multimode fiber and patch cables you are using right now, but get 40G performance. So data center managers won’t worry about the high cost of changing cable plant. Besides, compared to traditional QSFP+ transceivers, BiDi QSFP+ transceivers uses fewer fibers (about 2 fibers) to support 40G signal transmission, which can save another amount of money for you. For example, if you are building a new 40G data center fabric in the traditional way, you would need to run 8-multimode fiber strands between your access and aggression layer: a cost of $2000 per port. However, with BiDi QSFP+ transceivers, you can get 40G performance using just 2 fiber strands: a quarter of cabling. For a standard server rack (384 ports), that translates to a savings of more than $550,000.

Conclusion

Through the information we have discussed above, there is no doubt that 40G BiDi QSFP+ transceiver is really a cost-effective solution for the migration from 10G to 40G network. Although the price of BiDi QSFP+ transceivers are higher than that of common QSFP+ transceivers, BiDi QSFP+ transceiver utilizes much fewer fibers per unit distance. For many networks, the cost savings of utilizing less fibers far exceed the higher purchase price of BiDi QSFP+ transceivers. With advanced manufacturing facilities, strict reliability test and quality control, FS.COM ensures that our customers can get the highest-quality BiDi QSFP+ transceivers with the lowest price. We also provide plenty of traditional QSFP+ transceiver modules, like Cisco 40G-QSFP-CSR4, for your needs. Besides QSFP+, there are also many other types of fiber optic transceivers for different Ethernet networks, such as SFP, SFP+, 100G QSFP28. If you are looking for any related products, please visit FS.COM or contact sales@fs.com.

Things You Should Know About BiDi SFP Modules

For the past few years, SFP transceiver modules have received much attention and widely used in telecommunication or communications applications. It is known that almost all modern SFP modules use two fibers to transmit data. One is to receive data from networking equipment, and the other is to transmit data to the networking equipment. However, in recent years, a new type of SFP transceiver is available—Bi-Directional SFP (BiDi SFP) transceiver, which can both transmit and receive data to/from interconnected equipment through a single optical fiber. This post tends to introduce BiDi SFP from the perspectives of definition, working principle, and differences from common SFP modules.

What Is BiDi SFP?

BiDi SFP transceiver is a compact optical transceiver module which uses WDM (wavelength division multiplexing) technology and is compliant with the SFP multi-source agreement (MSA). It is specially designed for the high performance integrated duplex data link over a single optical fiber. BiDi SFP interfaces a network device mother board (for a switch, router or similar device) to a fiber optic or unshielded twisted pair networking cable. Nowadays, it is one of the most popular industry formats supported by many fiber optic component vendors. Here is a Cisco BiDi SFP produced by FS.COM.

Working Principle of BiDi SFP

Compared to traditional SFP transceiver, BiDi SFP are deployed in matched pairs. One for the upstream (“U”) direction, and the other for the downstream (“D”), each part is transmitting at a different wavelength. We could get intuitive understanding of how BiDi SFP works from the image below. The two wavelengths utilized in this example are 1310 nm and 1550 nm. (1310 nm/1550 nm or 1550 nm/1310 nm are commonly used wavelengths in BiDi SFP). Typically, the upstream or “U” transmits at the shorter of the two wavelength—1310 nm, while the downstream or “D” the longer wavelength—1550 nm.

Main Differences Between BiDi SFP and Traditional SFP

The primary difference between BiDi SFP and traditional two-fiber SFP transceiver is that BiDi SFP is fitted with wavelength division multiplexing (WDM) couplers, also known as diplexer, which combine and separate data transmitted over a single fiber based on the wavelengths of the light. That’s why BiDi SFP has only one port, while the traditional SFP module is generally with two ports. One is TX for the transmitting port, and the other is RX for receiving port. The following picture shows different port structures of common Cisco SFP and BiDi SFP.

Another difference between common SFP and BiDi SFP is upon optical sub-assemblies, major cost components of a fiber optic transceiver. As we all know, a common SFP usually has two optical sub-assemblies—the transmitter optical sub-assembly (TOSA) and the receiver optical sub-assembly (ROSA), but BiDi SFP only contains one optical sub-assemblies—BOSA (bi-directional optical sub-assembly), which acts the role of TOSA and ROSA, but with different working principle.

Applications of BiDi SFP

At present, the BiDi SFP is usually used in FTTx deployment P2P (point to point) connection. For example, in a FTTH deployment, optical fibers are used directly to connect the central office and the customer premises equipment. But because the use of P2P architecture, the customer premises equipment has to be connected to the central office on a dedicated fiber. Thanks to BiDi SFP, which allows a bi-directional communication on a single fiber by using wavelength division multiplexing (WDM), the connection between central office and customer premises equipment becomes more simple. Besides this application, BiDi SFP can be also applied in WDM fast Ethernet links, metropolitan area network, and inter-system communication between servers, switches, routers, OADM, etc.

Conclusion

BiDi SFP breaks the rules of traditional SFP modules in many aspects, which have been discussed in the above part. After reading this article, we could get some understanding of BiDi SFP including its definition, working principle and differences from traditional SFP modules. The biggest valuable advantage of BiDi SFP is that it can save cost on optical fiber, especially in long-haul fiber optic transmission. And believe it or not, with the development of technology, it will have broad market prospect.

How Much Do You Know About Fiber Optic Transceiver?

Fiber Optic Transceiver(Transmitter and Receiver)

Fiber Optic Transceiver, also called fiber optic transmitter and receiver, is a device which includes a LED or laser source and signal conditioning electronics that is used to inject a signal into fiber. It is composed of three basic functional modules, including optoelectronic devices, the optical signal interface and the functional circuit. Optoelectronic devices includes a transmitter and receiver.

Information is sent from a source to a transmitter by means of an electricity signal. The transmitter then takes an electrical input and transfers it to an light signal. The light signal from the transmitter is coupled into the fiber with a connector and is transmitted through the fiber optic cable plant until it reaches a receiver. The fiber optic receiver captures the light from a fiber optic cable, decodes the data it is sending and then converts the light signal into an electricity signal. A transceiver is a device which combines the functions of both the transmitter and receiver.

Sources for Fiber Optic Transmitter

The sources used for fiber optic transmitters need to meet several criteria: it has to be at the correct wavelength, can be modulated fast enough to convert data, and be able to be coupled into the fiber. LEDs, fabry-petrot (FP) lasers, distributed feedback (DFB) lasers and vertical cavity surface-emitting lasers (VCSELs) are the four commonly used types of sources for a transmitter which can convert electricity signals into light signals. They are tiny semiconductor chips. FP lasers emit light from the side of the chip, while the LEDs and VCSELs are fabricated on semiconductor wafers so that they emit light from the surface of the chip.

Detectors for Fiber Optic Receiver

Fiber optic receivers use semiconductor detectors (photodiodes or photodectors) to convert light signals into electricity signals. Silicon photodiodes are used for short wavelength links (650 for plastic optical fiber and 850 for glass multimode optical fiber ), while InGaAs (indium gallium arsenide) detectors are usually used for long wavelength, because InGaAs detectors have lower noise than germanium that allows for more sensitive receivers.

Types of Fiber Optic Transceiver

There are a number of fiber optic transceivers available in the market. And they differ in the type of connections, data transmission speed, as well packing forms. According to the package, there are several commonly used types of fiber optic transceiver, including SFP, SFP+, XFP, QSFP, GBIC.

SFP Transceiver: SFP is the abbreviation of Small Form Factor Pluggable, which is used for the conversion of light and electricity signals. SFP is a mini version of GBIC, and it has all the functions of GBIC, for example it can transmit over one gigabit signals and it is hot-pluggable. Because SFP modules can be easily interchanged, it is more convenient for people to upgrade and maintain fiber optic networks than has been the case with traditional modules. A single SFP module can be removed and replaced for repair or upgrading, which can save substantial cost both in maintenance and in upgrading efforts. It interfaces a network device motherboard (for a switch, router, media converter or similar device) to a fiber optic networking cable.

SFP+ Transceiver: The SFP+ transceiver whose full name is Enhanced Small Form Factor Pluggable, is a kind of fiber optic transceiver to achieve the conversion of light and electricity signals. SFP+ transceiver is an enhanced version of the SFP that can transmit data rates up to 10 Gbps. It has the same appearance and connector as the SFP, but it can provide a higher speed than SFP. In general, when a SFP can support over 8Gbps, it can be called as SFP+.

XFP Transceiver: The XFP (10 Gigabit Small Form Factor Pluggable)is a hot-swappable and protocol-independent fiber optic transceiver for the conversion of light and electricity signals in high-speed computer network and telecommunication links which use fiber optics. Before the XFP was created, the transmission speed could only reach 1.25Gbps, 2.5Gbps or 4Gbps. But this speed is not able to adapt to the development of network. Thus a XFP transceiver is designed to support 10G data per second which improves the communication speed greatly.

QSFP Transceiver: The QSFP (Quad Small Form Factor Pluggable) is a compact, hot-pluggable transceiver used for data communication applications, and it interface networking hardware to a fiber optic cable or active or passive electric copper connection. With the development of technology in the field of networking, QSFP is designed to achieve higher data rates, which enables the data transmission rate to reach as high as 40Gbps. QSFP enhances work efficiency to a large extent, with its high-density, compact size, and low power consumption.

GBIC Transceiver: GBIC transceiver means Gigabit Interface Converter. It converts light signals to electricity signals, and electricity signals to light signals. It is the first standardized fiber optic transceiver which was typically used in fiber optic and Ethernet systems as an interface for high-speed networking. And its data transfer rate could reach one gigabit per second. With the appearance of GBIC, people could achieve long distance communication in spite of the limitation of bandwidth. However, with the fast development of technology, it cannot meet the demand of people any more. And with more and more better transceiver created, GBIC transceiver is no longer popular and is replaced gradually.

Fiber Optic Transceiver is an important device used for the transition of light and electricity in fiber optic communication. According to different capacity need, there are different connectors of fiber optic transceivers. With the help of this article, it will be easier for users to choose a right transceiver they need.