FAQs About Compatible SFP Modules

SFP (small form-factor pluggable) was jointly developed by many of the world's leading network vendors. It has been widely used in optical network systems. Nowadays, many 3rd party SFP module vendors are providing high quality and reliable compatible SFP transceiver modules with low prices, such as compatible Cisco gigabit SFP, and using 3rd party SFP modules seems to be more and more popular now. Whether to choose compatible SFP modules or not? Here are some common questions that you might ask when using compatible SFP transceivers. Hope these answers can help you get a better understanding of compatible SFP modules.

1. What does 1000BASE-T or 1000BASE-X mean?

1000BASE-T is Gigabit Ethernet on copper cables, using four pairs of Category 5 unshielded twisted pair to achieve the gigabit data rate. 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. A big advantage of 1000BASE-T is that existing copper cabling can be used instead of having to rewire with optical fiber. 1000BASE-X is a group of standards for Ethernet physical layer standards, specified within the IEEE 802.3.z standard. It is used for Gigabit Ethernet connections that transmit data mainly over fiber optic cable. The standards that apply to the term 1000BASE-X include -LX, -SX, -BX10, -LX10, as well as non-standard -ZX and -EX standards. All of the standards that are grouped at 1000BASE-X utilize a 8b/10b encoding where 8 bits are reserved for data transmission while 2 bits are used for error correction.

2. How does transceiver compatibility work?

Each module holds its own information in EEPROM, and this memory is coded with unique identifiers such as part numbers and manufacturers details. The firmware of the host device then checks the memory for the correct information to confirm compatibility.

3. Why does my compatible SFP not work with the host device?

This is a common problem, a large amount of host devices do not have a firmware check for compatibility, this is known as an "open platform". Many SFP transceivers are sold as compatible when in fact they are open platform. They will work in many host devices but not in any that require coded transceivers. OEM SFP transceivers are coded specifically to suit each host device to avoid this problem, such as HP J4859C (as shown below) and HP JD118B SFP modules.

 

4. Will compatible SFP modules affect my host device warranty?

No, host device warranty will be unaffected. Please note that host device warranties do not cover SFP transceiver modules, OEM vendors offer lifetime warranties to protect them.

5. What is DOM support?

DOM, short for digital optical monitoring, is a feature used to monitor some parameters of the transceiver in real-time, helping to identify the location of the fiber link failure, simplify maintenance, and improve system reliability. DOM allows you to monitor the TX (transmit) and RX (receive) power of the module, temperature, and transceiver supply voltage. With DOM, network administrators can check and ensure that the module is functioning correctly in an easy and convenient way. This is why most of modern optical SFP transceivers support DOM functions.

6. Why choose compatible SFP modules?

In fact, most of the networking manufacturers do not produce their own SFP, XFP, SFP+, X2 transceivers, etc. They buy OEM transceivers, label them with their own brand and sell at a much higher price. You are basically paying a high price to have the respective manufacturers logo on the equipment. Besides, many compatible transceivers are made and assembled in exactly the same plants assembling officially-branded transceivers. There is almost no big difference between an official transceiver and a third-party plug, aside from the branding and about two hundred to a few thousand bucks.

7. How to identify the refurbished SFP module?

Here are three methods. First one is appearance recognition. Check the appearance of the SFP module. A new SFP module's appearance generally has good consistency while a refurbished SFP module is not glossy, and has some wear and scratches in the rim angle. Many refurbished SFP modules are replaced with new shells. If there is dust in the interface or the interface is not smooth, it is refurbished SFP module. Then you can check the ferrule. Pulling out the dust cap, you can see the ferrule in the bore. A second-hand old module is not glossy, and generally rough and with scratches, and it has a bad consistency. The ferrules of a new quality module is bright with color and lustre and has a good consistency. Last, you can put the module under the status of 50-60°C and see whether it can work properly. In general, a refurbished SFP module can not work well or even disconnect.

Summary

Various vendor-coded SFP modules are compatible to widespread networking equipment from well-known manufacturers. Fiberstore provides a variety of SFP transceiver modules that are compatible to devices of important vendors in the market. From production to shipmet, all these compatible SFP modules are tested and guaranteed 100% compatible and with high qulity.

1000BASE-What?

There are many kinds of optical transceiver in the market. When looking at a transceiver module, you may see words like 1000BASE-CX, 1000BASE-SX, 1000BASE-T, and so on. For example, the following picture shows a 3CSFP91 compatible SFP transceiver. You can see "1000BASE-SX SFP" on it. What do they mean? And what's the difference between 1000BASE-SX, 1000BASE-CX, and 1000BASE-T? In this post, a brief introduction to 1000BASE will be given.

What Does 1000BASE Mean?

The "1000" refers to the transmission speed of 1000Mbps. In computer networking, Gigabit Ethernet (GE or 1GbE) is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE 802.3-2008 standard. The cables and equipment are very similar to previous standards and have been very common and economical since 2010. You may wonder what the word "BASE" means. BASE refers to "baseband", meaning that this is an unfiltered line not requiring a digital modulation scheme. Back in the day, there was a 10PASS-TS version of Ethernet that used a signaling scheme similar to a modem, but baseband is dominant today. So 1000BASE refers to a Gigabit Ethernet connection that uses the unfiltered cable for transmission.

1000BASE-What?

The next part is the cabling used to carry the signals. The earliest forms of Ethernet used coaxial cable, but thin twisted-pair cabling became popular in the mid-1990s. Faster versions of Ethernet also often use fiber optics rather than electrical signals. There are a bewildering assortment of physical interconnects for Ethernet. But the naming system isn't as complex as it might appear. The first letter tells us which kind of wire we are talking about:

• "S" means short-range multi-mode optical cable (less than 100 m)
• "L" means long-range single- or multi-mode optical cable (100 m to 10 km)
• "E" means extended-range optical cable (10 km to 40 km)
• "Z" means long-range single-mode cable at a higher wavelength
• "T" means twisted-pair cable (e.g. the common Category 5 in use today)
• "K" means a copper backplane
• "C" means balanced copper cable
• "B" uses two wavelengths over a single optical cable

Next is the coding scheme for data on the wire: "X" means 8B/10B block coding for Gigabit Ethernet. Then, we have a number representing the number of parallel "lanes" for data: "1" would mean serial (non-parallel) but is omitted instead; "4" or "10" are available for copper wire; just about any other number could be used for optical lanes or wavelengths. As you can see, common unshielded twisted pair wiring is "BASE-T", optics are denoted according to their range ("S", "L", "E"), and backplanes use "K" copper.

Examples

1000BASE-SX standard is a variant coupled to a VCSEL laser with a short wavelength of 850nm. It has a maximum length of 550 meters. 1000BASE-SX technologies are being widely implemented in enterprise-level networks and primarily used between pieces of equipment within a building. 1000BASE-LX standard has a working distance of up to 5 km over single-mode optic fiber. And it can also be used to transmit data over common multi-mode fiber options with a maximum length of 550m. 1000BASE-EX standard is capable of transmitting up to 40 km over a single-mode optic fiber pair due to higher quality optics. 1000BASE-CX is an initial standard for Gigabit Ethernet connections with maximum distances of 25 meters using balanced shielded twisted pair. 1000BASE-KX standard is for Ethernet operation over electrical backplanes. It defines one to four lanes of backplane links, one RX and one TX differential pair per lane. The 1000BASE-KX variant uses 1.25GBd electrical (not optical) signalling speed. 1000BASE-T normally uses four pairs of the commonly installed Category 5 unshielded twisted pair (UTP) cable or enhanced category 5 cabling version of UTP cabling to achieve gigabit data rates. The image below shows a Moxa SFP-1GLSXLC 1000BASE-LX SFP transceiver.

There are various 1000BASE SFP transceivers available depending on the your application and distance capability required. Fiberstore is a professional manufacturer and supplier, offering various kinds of 1000BASE SFP transceivers 100% compatible with major brands like Cisco, HP, Juniper, Force10, D-link, 3Com. They are backed by a lifetime warranty, and we also can customize optical transceivers to fit your specific requirements.

1000BASE-T Gigabit Ethernet over Category 5 Cable

Various copper and fiber choices are available on the market today. When deciding a cabling system, network managers should know how to choose the most appropriate cabling system for their network infrastructure in the long run. Many of the cabling installed today inside buildings is Category 5. Many factors, like punch down blocks, and patch panel connections, affect the performance of 1000BASE-T technology if not correctly implemented. This article gives an introduction to 1000BASE-T Gigabit Ethernet operation over the installed base of Category 5 cabling.

1000BASE-T and Category 5 Cabling

1000BASE-T is a type of gigabit Ethernet networking technology that uses copper cables as a medium. 1000BASE-T uses four pairs of Category 5 unshielded twisted pair cables to achieve gigabit data rates. There should be no need to replace existing Category 5 cabling to use 1000BASE-T. The standard is designated as IEEE 802.3ab and allows 1Gbps data transfers for distances of up to 330 feet. 1000Base-T came into wide use in 1999, gradually replacing fast Ethernet for wired local networks simply because it was 10 times as fast. Equipment and cables are very similar to previous Ethernet standards and by 2011 were very common and economical. These were the biggest factors that ensured this standard's wide acceptance. The 1000BASE-T product is designed to operate over Category 5 cabling. The image below shows how 1000BASE-T works.

Gigabit Bandwidth over Category 5 Cabling

1000BASE-T uses a symbol rate of 125 Mbaud (A 125 Mbaud symbol rate is required because 100BASE-TX uses 4B/5B coding), but it uses all four pairs for the link and a more sophisticated five-level coding scheme. In addition, 1000BASE-T sends and receives simultaneously on each pair. Combining 5-level coding and 4 pairs allows 1000BASE-T to send one byte in parallel at each signal pulse. 4 pairs 125 Msymbols/second X 2 bits/symbol = 1Gbps.

Problems During Cable Installation

Of course, it isn't quite this simple. In addition to moving the symbols across the link, 1000BASE-T must also deal with the effects of return loss and crosstalk, and other factors.

Return loss measures the amount of reflected signal energy resulting from impedance changes in the cabling link. If too much energy is reflected back onto the receiver, the device does not perform optimally. Factors that affect the return loss are:

• The number of transition points, as there is a connection through an RJ-45 to another connector, a patch panel, or device at each transition point.
• Removing the jacket that surrounds the four pairs of twisted cable. When RJ-45 connections are made, this is minimized to 1 1/4 inch (32 mm).
• Untwisting any pair of the twisted-pair cabling. It is important that any untwisting be minimized to 3/8 inch (10 mm) for RJ-45 connections.
• Cabling or bundling of multiple Category 5 cables. If not correctly implemented, this can adversely affect all cabling settings.

Crosstalk is unwanted signals coupled between adjacent wire pairs. Since 1000BASE-T uses all four wire pairs, each pair is affected by crosstalk from the adjacent three pairs. Near-end crosstalk (NEXT) is crosstalk that appears at the output of a wire pair at the transmitter (near) end of the cable. Far-end crosstalk (FEXT) is a measure of the unwanted signal coupling from a transmitter at the near-end into a neighboring pair measured at the far-end. Crosstalk is characterized in reference to the transmitter.

Conclusion

For optimum performance of your 1000BASE-T product, it is important to fully qualify your cable installation and ensure that it meets or exceeds Category 5 specifications. Fiberstore provides various Category 5 cables and 1000BASE-T optical transceivers for your applications. For example, Finisar FCLF-8520-3 1000BASE-T copper SFP RJ-45 transceiver, and Cisco GLC-T 1000BASE-T SFP copper RJ-45 transceiver, are compliant with the Gigabit Ethernet and 1000BASE-T standards as specified in IEEE 802.3 and 802.3ab. These SFP transceivers link your switches and routers to the network. They are 100% functionally tested, and compatibility is guaranteed.