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The Basics of 1000BASE-SX and 1000BASE-LX SFP

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Gigabit Ethernet has been regarded as a huge breakthrough of telecom industry by offering speeds of up to 100Mbps. Gigabit Ethernet is a standard for transmitting Ethernet frames at a rate of a gigabit per second. There are five physical layer standards for Gigabit Ethernet using optical fiber (1000BASE-X), twisted pair cable (1000BASE-T), or shielded balanced copper cable (1000BASE-CX). 1000BASE-LX and 1000BASE-SX SFP are two common types of optical transceiver modules in the market. Today’s topic will be a brief introduction to 1000BASE-LX and 1000BASE-SX SFP transceivers.

1000BASE in these terms refers to a Gigabit Ethernet connection that uses the unfiltered cable for transmission. “X” means 4B/5B block coding for Fast Ethernet or 8B/10B block coding for Gigabit Ethernet. “L” means long-range single- or multi-mode optical cable (100 m to 10 km). “S” means short-range multi-mode optical cable (less than 100 m).

1000BASE-SX
1000BASE-SX is a fiber optic Gigabit Ethernet standard for operation over multi-mode fiber using a 770 to 860 nanometer, near infrared (NIR) light wavelength. The standard specifies a distance capability between 220 meters and 550 meters. In practice, with good quality fiber, optics, and terminations, 1000BASE-SX will usually work over significantly longer distances. This standard is highly popular for intra-building links in large office buildings, co-location facilities and carrier neutral internet exchanges. 1000BASE-SX SFP works at 850nm wavelength and used only for the purposed of the multimode optical fiber with an LC connector. 1000BASE-SX SFP traditional 50 microns of multimode optical fiber link is 550 meters high and 62.5 micron fiber distributed data interface (FDDI) multimode optical fiber is up to 220 meters. Take EX-SFP-1GE-SX as an example, its maximum distance is 550m with DOM support. The 1000Base-SX standard supports the multimode fiber distances shown in table 1.

1000Base-SX standard

1000BASE-LX
Specified in IEEE 802.3 Clause 38, 1000BASE-LX is a type of standard for implementing Gigabit Ethernet networks. The “LX” in 1000BASE-LX stands for long wavelength, indicating that this version of Gigabit Ethernet is intended for use with long-wavelength transmissions (1270–1355 nm) over long cable runs of fiber optic cabling. 1000BASE-LX can run over both single mode fiber and multimode fiber with a distance of up to 5 km and 550 m, respectively. For link distances greater than 300 m, the use of a special launch conditioning patch cord may be required. 1000BASE-LX is intended mainly for connecting high-speed hubs, Ethernet switches, and routers together in different wiring closets or buildings using long cabling runs, and developed to support longer-length multimode building fiber backbones and single-mode campus backbones. E1MG-LX-OM is Brocade 1000BASE-LX SFP that operates over a wavelength of 1310nm for 10 km.

1000BASE-LX SFP

Difference Between LX, LH and LX/LH
Many vendors use both LH and LX/LH for certain SFP modules, this SFP type is similar with the other SFPs in basic working principle and size. However, LH and LX/LH aren’t a Gigabit Ethernet standard and are compatible with 1000BASE-LX standard. 1000BASE-LH SFP operates a distance up to 70km over single-mode fiber. For example, Cisco MGBLH1 1000BASE-LH SFP covers a link length of 40km that make itself perfect for long-reach application. 1000BASE-LX/LH SFP can operate on standard single-mode fiber-optic link spans of up to 10 km and up to 550 m on any multimode fibers. In addition, when used over legacy multimode fiber type, the transmitter should be coupled through a mode conditioning patch cable.

Conclusion
1000BASE SFP transceiver is the most commonly used component for Gigabit Ethernet application. With so many types available in the market, careful notice should be given to the range of differences, both in distance and price of multimode and single-mode fiber optics. Fiberstore offers a large amount of in-stock 1000BASE SFP transceivers which are compatible for Cisco, Juniper, Dell, Finisar, Brocade, or Netgear in various options. If you have any requirement of our products, please send your request to us.

Knowledge of SFP Auto-Negotiation

We usually see fiber optic transceiver with descriptions like “10/100/1000 copper SFP” shown in the picture below. Then what does “10/100/1000” mean? In fact, it refers to SFP modules that support 10/100/1000 auto-negotiation. With the function of auto-negotiation, SFP can operate on 10 Mbps, 100 Mbps, and 1000 Mbps. Some knowledge of SFP auto-negotiation will be given in this article.

Auto Negotiation Copper SFP

What Is Auto-Negotiation?

Today a number of technologies, such as 10Base-T, 100Base-T, and 1000Base-T, use the same RJ-45 connector, creating the potential for connecting electrically incompatible components together and causing network disruption. To eliminate the possibility of dissimilar technologies interfering with each other, the Institute of Electrical and Electronics Engineers (IEEE) developed a protocol known as auto-negotiation. Auto-negotiation allows devices to perform automatic configuration to achieve the best possible mode of operation over a link. Devices with this feature will broadcast their speed (10 Mbps, 100 Mbps, and 1000 Mbps) and duplex (half/full) capabilities to other devices and negotiate the best between two devices.

Types of SFP Auto-Negotiation

There are two types of auto-negotiation that operate simultaneously within the SFP module. One is the 1000Base-T auto-negotiation, the other is 1000BASE-X auto-negotiation. The difference between them is that 1000BASE-T auto-negotiation is conducted over the Cat 5 cable between the two 1000BASE-T devices while 1000BASE-X auto-negotiation is typically conducted between two host systems over fiber. Usually, Gigabit SFP transceivers use auto-negotiation to advertise the following modes of operation: 1000Base-T in full or half duplex, 100Base-TX in full or half duplex, and 10Base-T in full or half duplex.

SFP Auto-Negotiation in Real Applications

A few cases of how SFP auto-negotiation operation works in an actual application are shown below:
Case1: A SFP is inserted into a switch with no copper cable.
Regardless of whether the MAC has 1000Base-X auto-negotiation turned on or off, 1000Base-X auto-negotiation will not complete. Because 1000Base-X auto-negotiation will never complete before 1000Base-T link is established.

Case2: After SFP is inserted into a switch w/ 1000Base-X auto-negotiation, copper cable is inserted.
SFP will store the 1000Base-X abilities advertisements from the MAC. 1000Base-T auto-negotiation will be restarted using abilities advertisements from the MAC. After 1000Base-T link is completed, SFP will send 1000Base-X abilities advertisements and acknowledgement codewords to the MAC. 1000Base-X link will then be established.

Case3: After SFP is inserted into a switch w/ no 1000Base-X auto-negotiation, copper cable is inserted.
SFP will detect that only idles are received from the MAC. 1000Base-T link will be established based on abilities set by hardware strap options on the PHY. After 1000Base-T link is established, the SFP will wait for 200 minutes and go into bypass mode. 1000Base-X link will then be established.

Case4: Both 1000Base-T and 1000Base-X link has been established. Copper cable is then unplugged.
When the copper cable is unplugged, 1000Base-T link will be broken. This will restart auto-negotiation both for 1000Base-X and 1000Base-T.

Case5: Copper cable is first plugged into the SFP, then SFP with cable is inserted into switch.
This case is the same case 2 and 3. If the SFP is powered up with copper cable already plugged in, it will go through the same auto-negotiation process.

After reading this article, you may know more about SFP auto-negotiation. Fiberstore have a lot of 10/100/1000BASE-T auto-negotiation 100m RJ45 copper SFP fiber optic transceivers in stock with high quality and low price. For more information, please visit fs.com.