Dig Deeper Into SFP Transceivers

Small form-factor pluggable (SFP) is a prevailing type of optical transceivers in the market widely utilized for Gigabit Ethernet application. As it has the same function with GBIC but with a smaller size, SFP transceiver is also called mini-GBIC. Optical transceivers are typically designed to both transmit and receive electrical optical signals under the Multi-Source Agreement. Each SFP module can support data rates from 1Gbps to 10Gbps. And there are a number of SFP modules and network accessories available for you to select from. Which one suits you better? The following article will dig deeper into the SFP transceivers that will help decide which one will work best for you.

SFP transceivers have a variety of different transmission and receiving type, users can select the appropriate transceiver for each link, to provide the optical performance can be achieved based on the available fiber type (such as a multimode fiber or single-mode fiber). Optical SFP modules available are generally divided into the following categories. Figure 1 displays the basic components of a SFP transceiver.

 

1000BASE-LX—Specified in IEEE 802.3 Clause 38, 1000BASE-LX uses a long wavelength laser (1270-1355 nm), and a maximum RMS spectral width of 4nm. 1000BASE-LX is designed to cover a distance of up to 10 km over 10µm single-mode fiber. 1000BASE-LX can also run over all common types of multimode fiber with a maximum segment length of 550 m. For link distances greater than 300 m, the use of a special launch conditioning patch cord may be required. E1MG-LX-OM is Brocade 1000BASE-LX SFP that can work over a distance of 10km.

1000BASE-EX—1000BASE-EX is not a standard but industry accepted term for Gigabit Ethernet transmission. It is very similar to 1000BASE-LX10 but achieves longer distances up to 40 km over a pair of single-mode fibers due to higher quality optics than a LX10, running on 1310nm wavelength lasers. It is sometimes referred to as LH (Long Haul).

1000BASE-ZX—1000BASE-ZX is also a non-standard but multi-vendor term using 1,550nm wavelength to achieve distances of at least 70 kilometers over single-mode fiber. Some vendors can specify distances up to 120 kilometers over single-mode fiber. Ranges beyond 80 km are highly dependent upon the path loss of the fiber in use, specifically the attenuation figure in dB per km, the number and quality of connectors/patch panels and splices located between transceivers.

1000BASE-SX—1000BASE-SX is a Gigabit Ethernet standard for operation over multimode fiber using a 770 to 860 nm, near infrared (NIR) light wavelength for a maximum of 550m at 1.25 Gbit/s (gigabit Ethernet) or 150m at 4.25 Gbit/s (Fibre Channel). Take EX-SFP-1GE-SX as an example, it is 1000BASE-SX SFP that can support a link length of 550m over OM2 cable. Figure 2 shows that EX-SFP-1GE-SX inserts into a Juniper SRX210.

 

1000BASE-BX10—1000BASE-BX10 is capable of up to 10 km over a single strand of single-mode fiber, with a different wavelength going in each direction. The terminals on each side of the fiber are not equal, as the one transmitting downstream uses the 1490nm wavelength, and the one transmitting upstream uses the 1310nm wavelength.

1000BASE-T—It is a standard for Gigabit Ethernet copper cabling. The maximum length of 1000GBASE-T is 100 meters. 1000BASE-T must use Category 5 cable or better (including Cat 5e and Cat 6. 1000BASE-T can be used in data centers for server switching, for uplinks from desktop computer switches, or directly to the desktop for broadband applications.

1000BASE-TX—Created by the Telecommunications Industry Association (TIA), 1000BASE-TX (TIA/EIA-854) is a standard similar to 1000BASE-T that was simpler to implement. Compared with 1000BASE-T, this simplified design would have reduced the cost of the required electronics by only using two unidirectional pairs in each direction instead of 4 bidirectional. However, this solution has not been widely used largely due to the required Category 6 cabling and the rapidly falling cost of 1000BASE-T products.

Recommended Information It is known that there is no visual difference between the bare SFP modules, so how to differ them? Smart manufacturers figure a way out by marking the color of pull ring to distinguish generally. For example: black pull ring is multimode, the wavelength is 850 nm; blue is the 1310nm module; yellow is the 1550nm module; purple is the 1490nm module and so on. If you are confused with the specifications of the SFP modules, you should find a reliable vendor to help you. Fiberstore provides a variety of SFP modules including 100BASE SFP, 1000BASE SFP, BiDi SFP, CWDM/DWDM SFP, SONET/SDH SFP and 2G/4G FC SFP. Our SFP modules are fully compatible with major brand. For more information about SFP transceivers, please feel free to contact us.

Basic Information About Fiber Optic Transceiver

Optical fiber transceivers are also called fiber optic transmitter and receiver, which are used to send and receive optical information in a variety of different applications. The role of the optical module is photoelectric conversion. These optical modules are scalable and flexible in their use, and this is why they are preferred by designers. Here is what you need to know about the basics of fiber optic transceivers.

Fiber Optic Transmitters and Receivers
Fiber optic transmission system consists of a transmitter on one end of a fiber and a receiver on the other end. The transmitter end takes in and converts the electrical signal into light, after the optical fiber transmission in the fiber cable plant, the receiver end again converts the light signal into electrical signal. Both the receiver and the transmitter ends have their own circuitry and can handle transmissions in both directions. Fiber optic cables can both send and receive information. The cables can be made of different fibers, and the information can be transmitted at different times. The following picture shows a fiber optic datalink.

Sources of Fiber Optic Transceiver
There are four types of fiber transmitters used to convert electrical signals into optical signals. These sources of fiber optic transmitters include: distributed feedback (DFB) lasers, fabry-perot (FP) lasers, LEDs, and vertical cavity surface-emitting lasers (VCSELs). They are all semiconductor chips. Take QSFP-40G-UNIV as an example, it is Arista QSFP-40G-UNIV compatible 40G QSFP+ transceiver. It uses DFB lasers as sources for fiber optic transmitters, which are used in long distance and DWDM systems. DFB lasers have the narrowest spectral width which minimizes chromatic dispersion on the longest links.

The choice of the devices is determined mainly by speed and fiber compatibility issues. As many premises systems using multi-mode fiber have exceeded bit rates of 1 Gb/s, lasers (mostly VCSELs) have replaced LEDs. Fiber optic transceivers are reliable, but they may malfunction or become out-dated. If an upgrade is necessary, there are hot-swappable fiber optic transceivers. These devices make it easy to replace or repair without powering down the device.

How Fiber Optic Transceiver Works?
Information is sent in the form of pulses of the light in the fiber optics. The light pulses have to be converted into electrical ones in order to be utilized by an electronic device. Thanks to the conversion by fiber optic transceivers: In its fiber optic data links, the transmitter converts an electrical signal into an optical signal, which is coupled with a connector and transmitted through a fiber optic cable. The light from the end of the cable is coupled to a receiver, where a detector converts the light back into an electrical signal. Either a light emitting diode (LED) or a laser diode is used as the light source.

Packaging
Optical fiber transceivers are usually packaged in industry standard packages like SFP, SFP+, XFP, X2, Xenpak, GBIC. According to the fiber type it connects to, there are MM (multi-mode), SM (Single-mode), as well as WDM fiber (CWDM, DWDM modules). The SFP modules support up to 4.25 Gbps with a connector on the optical end and a standard electrical interface on the other end. The QSFP are for 40 Gigabit networks using a LC duplex connection. Take compatible Brocade 40G-QSFP-LR4 as an example, it supports link lengths of 10km on single-mode fiber cable at a wavelength of 1310nm.

Summary
Keep in mind that fiber optic transceiver has two ends. One has an optical cable plug and another for connecting an electrical device. Each aspect of the transceivers is necessary to properly deliver a signal to its destination. Be aware of all aspects of fiber optic transceivers to purchase what you need for your application. Fiberstore supplies a wide variety of 40GBASE QSFP+ transceiver modules for you to choose from. More detailed, please contact us directly.

Classification of Transceiver Modules

Transceiver modules can be classified into different categories based on several different criteria. Package, transmission distance, wavelength, work rate, fiber mode, and connector type are all the common characteristics used for defining fiber optic transceivers. The following is a brief introduction to some of the characteristics used in classifying transceiver modules.

Package of Fiber Optic Transceiver
According to the optical module package, fiber optic transceivers can be divided into SFP, SFP+, XFP, GBIC, X2, XENPAK, QSFP+, PON, CSFP, CFP, 1X9 and SFF. Each package has its unique feature. Nowadays, SFP, SFP+, XFP and QSFP+ are the popular packages and they have been widely used in many fields, such as video communication field, aerospace, fiber to the home and so on. The image below shows a compatible HP SFP transceiver module.

Data Transfer Distance
In relation to data transfer distance, one major difference is multi-mode versus single-mode transceivers. For instance, a multi-mode transceiver will typically cover a distance of 100 m to 500 m. A single-mode transceiver can transmit a distance from 2 km to 120 km. This is an important aspect that people should consider when selecting a transceiver for an application. If the transmission distance is not adequate, the application will not work properly. Data transmission distance may be affected by whether the transceivers are single fiber or dual fiber.

Wavelength
Wavelength is the distance between repeating units of a propagating wave of a given frequency. Fiber optics transceivers transmit signal typically around 850, 1300 and 1550 nm. Multi-mode fiber is designed to operate at 850 and 1300 nm, while single-mode fiber is optimized for 1310 and 1550 nm.

Recent telecom systems use wavelength-division multiplexing (WDM), either DWDM (dense WDM) or CWDM (coarse WDM). For the fiber optic transceiver modules, the common wavelength (see in below image) includes 850 nm, 1279 nm, 1310 nm, 1330 nm, 1490 nm, 1510 nm, 1550 nm and 1610 nm. In the CWDM system, the wavelength range is from 1270 nm to 1610 nm, 20nm as a wave band. In the DWDM system, the wavelength range is also from 1270 nm to 1610 nm, but 0.8nm as a wave band.

Work Rate
The above type of classification brings two distinct types—full duplex mode and half duplex mode. The full duplex mode occurs when the data transmission is transmitted by two different transmission lines. There is communication at both ends of the device and is used for both sending and receiving operations. In this type of transceiver configuration, there is typically, no time delay generated by the operation.

The half-duplex mode is used with a single transmission line that is used for both reception and transmission. The communication cannot occur simultaneously in the same direction. That’s why it’s called the half-duplex system.

Managed Versus Unmanaged Transceivers
Unmanaged Ethernet optical transceivers are typically plug and play. They may have electrical interfaces with hardware DIP switch settings mode. With managed Ethernet fiber optic transceivers, they support a carrier-grade network management.

Conclusion
When you design for fiber optic transceiver, these classification criteria will come in handy. Fiberstore, as an professional telecommunication manufacturer, provides a large amount of fiber optic transceiver modules like SFP+ transceiver, X2 transceiver, XENPAK transceiver, XFP transceiver, SFP transceiver, GBIC transceiver, CWDM/DWDM transceiver, etc. J4858C, DS-SFP-FC8G-SW, DEM-310GT and Finisar FTLX1471D3BCL are all available at Fiberstore. They are fully compatible with major brand. If you have any question, please contact us directly.