A Quick Overview of Cisco GLC-LH-SM SFP Module

GLC-LH-SM is the Cisco 1000Base LX/LH SFP transceiver module, which is one of the most commonly used SFP module. It is hot-swappable and designed to plug directly into SFP/GBIC interface port or slot in your router and switch for Ethernet & Fibre Channel network applications. But in Match, 2013, Cisco announced the end-of-sale for GLC-LH-SM and substituted it with GLC-LH-SMD. But nowadays, there are still third party suppliers providing GLC-LH-SM SFP module, and there are still research results of it on the Internet. This article will give detailed introduction to the specification, advantages and common queries of GLC-LH-SM SFP.

Details of Cisco GLC-LH-SM Optical Module

Specifications of Cisco GLC-LH-SM SFP Optical Module

Cisco GLC-LH-SM optical module is characterized by a duplex LC type interface with a higher density as well as a smaller fiber optic connector. It could be used with both multimode fiber and single mode fiber. The GLC-LH-SM module is fully compatible with SFP Multi-Source Agreement (MSA). It is used in Gigabit network and its working distance could reach 10km max, data transfer rate at 1Gbps and it works based on IEEE 802.3z standards. The following chart shows detailed parameters of the Cisco GLC-LH-SM SFP optical module:

Advantages of Cisco GLC-LH-SM Optical Modules

First. Cisco GLC-LH-SM SFP optical module can function immediately without configuration, which saves installation time by leaving out this complicated procedure. It also offers internal calibration to optimize system’s data throughput.

Second. Cisco GLC-LH-SM SFP optical module is a hot swappable transceiver module, which features plug and play. Long before, a transceiver failure would cause a downtime and a lot of time to reconfigure new transceiver module. But now, with Cisco GLC-LH-SM SFP, you can just pop in the replacement without shutting down the whole system, and your network is back online.

Third. Cisco GLC-LH-SM SFP optical module could work with both multimode fiber and single mode fiber. When working with single mode fiber, the transmission distance can reach 10 km, suitable for long-distance transmission applications such as hospitals or campus network. While working with multimode fiber gives you maximum throughput upwards of 1.25 Gbps with the transmission distance as far as 550m.

Cisco GLC-LH-SM Compatible Switch Models

Cisco GLC-LH-SM is supported on a wide range of Cisco equipment. Here lists some of Cisco network switches compatible with GLC-LH-SM. For more switch models, you can find at this page: Cisco GLC-LH-SM.

Common Queries About Cisco GLC-LH-SM SFP Optical Module

GLC-LH-SM vs GLC-LH-SMD

It’s known to us all that Cisco has announced end-of-sale for GLC-LH-SM and replaced it with GLC-LH-SMD several years ago which aroused a buzz among network engineers. Literally, they look almost the same except the letter “D”. Then what’s the relationship between them and what’s the difference?

Similarity—Both Cisco GLC-LH-SM and Cisco GLC-LH-SMD transceiver modules are compatible with the IEEE 802.3z 1000BASE-LX/LH standard. They operate on standard single-mode fiber-optic link spans of up to 10km and up to 550m on any multimode fibers. They can be used interchangeably. When used over legacy multimode fiber type, Cisco GLC-LH-SM and Cisco GLC-LH-SMD should be coupled through a mode conditioning patch cable. In addition, both have dual LC/PC connector and work at 1300nm wavelength.

Difference—As stated before, Cisco SFP GLC-LH-SMD has an additional letter “D” while GLC-LH-SM SFP not. What does “D” mean? Some argue that “D” represents “duplex” and the other say it’s “rugged”. Actually, both of them are wrong. “D” stands for the digital diagnostic monitoring (DDM) function. So what can DDM actually do? Literally, DDM is able to provide component monitoring on transceiver applications in details like the real-time parameters. But that’s not all. DDM interface is an extension of the serial ID interface defined in GBIC specification and the SFP MSA. This DDM interface defines a sophisticated system of alarm and warning flags, which alerts end users when particular operating parameters are inconsistent with the factory-set normal range. So the DDM interface is also able to let the end users have the ability to achieve fault isolation and failure prediction. These all illustrate that GLC-LH-SMD has additional functions than GLC-LH-SM.

GLC-LH-SM vs GLC-SX-MM

Suppose you need to build a 600ft 10G network with Cisco 3650 modular switches and multimode 62mm fiber with LC ends, which transceiver module would you choose, GLC-LH-SM or GLC-SX-MM?

As both GLC-LH-SM and GLC-SX-MM optical module support multimode fiber, then which one would be a better choice? As shown in the below figure, the most evident difference is max cable distance. As a rule of thumb, multimode can't go as far as single mode. For multimode 62.5µm fiber and that short of a distance, GLC-SX-MM is a good choice. But if you're going longer than that on multimode or on singlemode fiber, GLC-LH-SM will do the work. At this point, some of you may say GLC-LH-SM seems to be more flexible but doubles the price than GLC-SX-MM. It’s only because you doesn’t find the right manufacturer. See the following table, the price difference of GLC-LH-SM and GLC-SX-MM is negligible and also with good quality.

Cisco GLC-LH-SM vs FS.com Cisco GLC-LH-SM

A quick Internet search of optical transceivers will yield wildly varying prices between OEM optics and many other third party optics suppliers. For example, 1000base SFP transceiver module may be priced as low as $10 to as high as $250. You may be shocked and confused by such a huge price disparity. Why OEM optics are many times as expensive as third party optics? What’s the difference between them and What should I choose? The next part will compare OEM Cisco GLC-LH-SM with compatible Cisco GLC-LH-SM supplied by FS.com.

Quality—We all know that Cisco GLC-LH-SM optical modules are OEM optics, which means that Cisco aren’t manufacturing themselves but ask other manufacturers to make optics for them and rebrand the transceiver module with their own logo. And then sell them to end users by distributors. In fact, most of factories in the world produce optical modules according to strict standards of MSA (Multisource Agreement), and they make the optics for every end users. So there is actually no difference in hardware for Cisco GLC-LH-SM and compatible Cisco GLC-LH-SM supplied by FS.com. Therefore, you may not concern about the quality.

Long Time Warranty—Then you may worry about warranty issue. FS.com, as a reliable third party optics supplier, offers a 5-year warranty on our products and provides great support service after your purchasing. When failures occur such as incompatibility issues with existing optics, FS.com will be able to troubleshoot and replace the optical modules for you quickly and at minimal to no cost. While Cisco only offer 1-year warranty. Most OEMs only provide few-year warranty. Here is the warranty list of some OEMs provide.

Price—The OEMs make huge profit from selling optics, so they always charge exorbitant prices for their optics. But third party optics are much cheaper than original ones. However, third party optics suppliers are numerous, and why choose FS.com? The price list of GLC-LH-SM will tell you answer.

According to aforementioned, there is no reason not to buy more cost-effective Cisco GLC-LH-SM optical modules on condition that both OEM and third party optics have the same quality and performance. Thus, FS.com is a worthwhile choice. We not only offer transceiver modules compatible with Cisco, but also other big brand such as HPE, Juniper, Arista etc. Most importantly, we have our own test center to ensure 100% compatibility all major vendors and systems, which is not covered by many third party optics suppliers.

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