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11 Nov 2015

Existing and emerging network technologies are driving the need for optical transceivers which support increased data rates in the data center. With the emergence of 1000BASE-LX specification, 1000BASE-LX/LH SFP transceiver module is widely used in optical network systems. Here are the most frequently asked questions we might have when using Cisco 1000BASE-LX/LH SFP (GLC-LH-SM or GLC-LH-SMD) transceivers.

1. Can 1000BASE-LX be compatible with 100BASE-LX?

1000BASE-LX and 100BASE-LX are very different standards. 1000BASE-LX SFP (GLC-LH-SMD) and 100BASE-LX SFP (GLC-FE-100LX) are two module types, one for GE and one for FE slots. The GLC-LH-SMD does not operate at 100Mbps. You will need to use a 100Mb module to connect to another device at 100Mb. Check optical transceiver compatibility with your equipment by reviewing the Cisco Fast Ethernet SFP module compatibility document and choose the one it says is compatible.


2. What is the difference between LH and LX modules?

The 1000BASE-LX, 1000BASE-LH and 1000BASE-LX/LH all refer to Gigabit Ethernet transmission. Among them, the 1000BASE-LX is a standard specified in IEEE 802.3 Clause 38 which uses a long wavelength laser, while the 1000BASE-LH and 1000BASE-LX/LH are just terms widely used by many vendors. Long Haul (LH) denotes longer distances while Long Wavelength (LX) denotes less energy which is obviously shorter distance. The 1000BASE-LX SFP modules compatible with the IEEE 802.3z 1000BASE-LX standard can achieve a distance up to 10km over single mode fiber. Unlike 1000BASE-LX SFP modules, 1000BASE-LH SFP modules operate at a distance up to 70km over single mode fiber.

3. Does 1000BASE-LX SFP work with 1000BASE-LH SFP? What does it mean if a module says like "Cisco 1000BASE-LX/LH SFP"?

Yes, the 1000BASE-LX works with the 1000BASE-LH. For instance, Cisco 1000BASE-LX/LH SFP is either made for single mode (long distance) / multimode (short distance). But this module can be used for both Single-mode and Multimode. The Cisco 1000BASE-LX/LH SFP, compatible with the IEEE 802.3z 1000BASE-LX standard, operates on standard single-mode fiber-optic link spans of up to 10 km and up to 550 m on any multimode fibers. When used over legacy multimode fiber type, the transmitter should be coupled through a mode conditioning patch cable.

4. GLC-LH-SM SFP to 1000BASE-LX GBIC won't link over MMF?

Cisco compatibility document says: "Some customers might be tempted to connect 1000BASE-LX/LH devices over short reaches of MMF jumper cables without MCP cables. There is a risk associated to this type of nonstandard deployment, especially when the jumper cable is an FDDI-grade or OM1 type. In such case the power coupled directly into a 62.5-micron fiber could be as high as a few dBm (typically 5 to 6 dBm), and if the jumper cable is short, the adjacent receiver will be saturated, causing high bit error rate, and eventually irreversibly damaged. We recommend the use of MCP, but if the customer remains reluctant to the deployment of MCP, a 5-dB attenuator for 1300nm should be used and plugged at the transmitter of the optical module on each side of the link."

5. Does GLC-LH-SMD work with GLC-LH-SM?

Yes. Both the GLC-LH-SM and GLC-LH-SMD transceivers support the IEEE 802.3 1000BASE-LX/LH standard and so are compatible with each other. The difference between the two is that the GLC-LH-SMD transceiver has additional support for Digital Optical Monitoring capability.

Fiberstore offers a wide range of 1000BASE-LX/LH SFP transceiver modules which are compatible with major brands, like Cisco, Juniper, Dell, Finisar, Brocade, or Netgear (AGM732F) in 10/20 km options. Fiberstore’s optical transceivers are able to fulfill enterprises, service providers, telecom operators and SAN providers to build and fulfill their existing and future network expansions. Besides the compatible 1000Base-LX/LH SFP modules, we also provide the 1000BASE-EX (like Cisco GLC-EX-SMD), 1000BASE-SX (like Cisco GLC-ZX-SM), 1000BASE-BX (like Cisco GLC-BX-D) and so on.


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