In recent decades, Cisco 1000BASE SFP transceivers have been widely used by many Ethernet users. There are many types of 1000BASE-LX/LH SFP transceivers on the market, such as Cisco GLC-LG-SM, GLC-LG-SM-RGD, GLC-LG-SM-20, which are operating on standard single-mode fiber-optic link spans of up to 10 km and up to 500 m on any multimode fibers. Among them, Cisco GLC-LG-SM and GLC-LG-SMD are two types of Cisco 1G SFP transceivers which are warmly welcomed by lots of Ethernet users. Do you know about them? And how to select? The detailed information about Cisco GLC-LG-SM and GLC-LG-SMD would be provided in the following passage.
The Cisco GLC-LH-SM 1000BASE-LX/LH Ethernet transceiver is a Duplex SFP transceiver for optical communications. It is fully compliant to Multi-Source Agreement (MSA), allowing it to function with other third party MSA compliant networking equipment. This 1000BASE SFP optical transceiver is capable of transmitting data at speeds of up to 1.25Gb/s over 10 km on single-mode fiber optic cable. The GLC-LH-SM uses an efficient 3.3 volt power supply and is designed to work best in temperatures between 0℃ and 50℃. The GLC-LH-SM’s Class 1 Laser operated at a wavelength of 1310 nm. The connector type is dual-LC. And it has no digital optical monitoring capacity. GLC-LH-SM is applicable to 1000BASE-LX/LH Ethernet and Gigabit Ethernet.
The following figure shows Cisco GLC-LH-SM 1000BASE-LX/LH SFP transceiver connecting with a Cisco Nexus 9396PX.
The Cisco GLC-LH-SMD module is designed for single-mode fiber and operates at a nominal wavelength of 1310 nm. The transmitter section uses a DFB laser. It operates data rate up to 1.25Gbps and up to 10 km over single-mode fiber. GLC-LH-SMD interfaces duplex LC connector interface. The working temperature is standard as commercial operating case temperature from 0℃ to +70℃. It is compliant with MSA SFP specification. Compared to Cisco GLC-LH-SM, Cisco GLC-LH-SMD has Digital Diagnostic Monitor (also called DOM or DDM) support. It interfaces with dual LC/PC connector. Cisco GLC-LH-SMD is applicable to Storage, IP network and LAN.
From the above two paragraphs, we can draw a conclusion that Cisco GLC-LH-SM and GLC-LH-SMD have many things in common, such as transmission distance, media type, using wavelength... They all support with IEEE 802.3 1000BASE-LX/LH standard and are compatible with each other, which means this two Cisco 1G SFP transceivers are interchangeable with each other. Besides, they also have identical prices at FS.COM, for $7 each.
The most obvious difference between Cisco GLC-LH-SM and GLC-LH-SMD is whether it has a DOM support or not. So what is DOM support? Digital Optical Monitoring or DOM is an industry wide standard, intended to define a digital interface to access real-time monitoring on SFP module’s temperature, receiver power, transmitter bias current, and transmitter. Digital Diagnostic Monitoring Interface (DDMI) available in Cisco SFP and SFP+ optical transceivers. The interface allows real time access to device operating parameters, and it includes a system of alarm and warning flags which alerts the host system when particular operating parameters are outside of a factory set normal operating. This interface is implemented with reference to SFF-8472, “Digital Diagnostic Monitoring Interface for Optical Transceivers”. Nowadays, many SFP transceivers have DOM support.
In this article, we are cleared that Cisco GLC-LH-SM and GLC-LH-SMD are 1000BASE SFP transceivers mainly used for 1G Ethernet transmission. And their major difference lies in DOM support. You can choose an appropriate one for yourself based on your need. If you need a monitoring and warning system for your transceiver, Cisco GLC-LH-SMD is highly recommended for 1G Ethernet networking. FS.COM offers large 1G SFP transceivers in-stock with low cost, which is compatible with many major brands in a variety of form factors. In addition, our products are free shipping right now in USA, Mexican and Australia. If you need any of our products, please feel free to contact us.