Comparison Between Cisco GLC-SX-MMD And GLC-SX-MM SFP

As a worldwide leader in IT and networking, Cisco SFPs have long enjoyed a good reputation in telecom market. With high flexibility, enhanced reliability and high compatibility, Cisco SFPs have been warmly welcomed by many Gigabit Ethernet users. At present, 1000BASE-T SFP for copper networks already could not meet the requirement of people’s calling for a new transceiver for a longer transmission distance. Under this situation, Cisco 1000BASE-SX SFP transceivers were developed, which can support up to 1 km over optimized 50 μm multimode fiber cable. Cisco GLC-SX-MM and Cisco GLC-SX-MMD are two different common types of Cisco 1000BASE-SX SFPs. They seem very similar in specification, but actually they are two different SFPs. So what are similarities and differences between Cisco GLC-SX-MM and Cisco GLC-SX-MMD? The detailed information will be fully covered in the following text.

Cisco GLC-SX-MM SFP

Cisco GLC-SX-MM SFP 1000BASE-SX SFP is fully covered in IEEE 802.3z. It operates at the wavelength of 850 nm. GLC-SX-MM Cisco is a duplex transceiver designed for multimode fiber (OM2) to connect equipment within short distance. It can be connected with LC connectors. The maximum transmission distance of GLC-SX-MM specs is 550 m at the data rate of 1Gbps.

Cisco GLC-SX-MMD SFP

Cisco GLC-SX-MMD is another type of 1000BASE-SX SFPs for transferring data within short distance. It has many commons with GLC-SX-MM SFP, and it can be regarded as the advanced version of Cisco GLC-SX-MM. SFP GLC-SX-MMD is compliant with SFP Multi-Source Agreement (MSA) standards. Just as Cisco GLC-SX-MM, the wavelength of GLC-SX-MMD is 850 nm, the media type is multimode fiber (OM2), the maximum transmission distance is 550 m... Different from GLC-SX-MM specs, GLC-SX-MMD Cisco can arrive the data rate at 1.25Gbps. Extended operating temperature range and DOM support are also main differences between them, which would be further explained in the next part.

Similarities:

• Multimode Fiber (OM2)
• 850nm Wavelength
• The maximum transmission distance is 550 m.
• Dual LC/PC connector

Differences： As we mentioned before, the extended DOM support splits the Cisco GLC-SX-MM SFP and Cisco GLC-SX-MMD SFP away. So what is the DOM support？

DOM stands for Diagnostic Optical Monitoring, which is used for monitoring parameters of the transceiver so as to simplify maintenance, identify the location of the fiber link failure and improve system reliability. It is compliant with SFF-8472 MSA and SFP MSA. Nowadays, many SFP transceivers have DOM support. DOM support has two main functions—monitoring and warning. On the one hand, digital diagnostics can monitor the SFP module’s temperature, receiver power, transmitter bias current, and transmitter power by a microcontroller inside the transceiver in a real time. On the other hand, DDM support offers a system of alarm and warning icon which alert the host system when particular parameters are not in line with the normal operating parameters set by the factory. In this way, uses could find out the fault isolation according to the displaying of DOM, and predict failure possibilities as well as prevent such fault at the same time.

Summary

This passage is mainly about the comparison between Cisco GLC-SX-MM and Cisco GLC-SX-MMD SFP transceivers. They have many things in common, such as using multimode fiber of media type, short distance transmission of 550 m, the wavelength of 850 nm...DOM support is a distinctive characteristics between Cisco GLC-SX-MM and Cisco GLC-SX-MMD. If you need DOM support to monitor parameters of the SFP, you can choose Cisco GLC-SX-MMD.