Difference Between Cisco GLC-LH-SM and GLC-LH-SMD

Routers and transistors have been in use since the explosive growth of technology. Along with them came about another gadget that helps in transmitting wavelengths of information and data.

It was called a transceiver. Some examples of the transceiver are GLC-LG-SM-RGD, GLC-LH-SM, GLC-LH-SMD, etc. They are types of SFP transceivers with their modules available for the manufacturer switches.


The main difference between Cisco GLC-LH-SM and GLC-LH-SMD is that while Cisco GLC-LH-SMD is compatible with DOM that helps in its digital monitoring and its optical capabilities Cisco GLC-LH-SM is incompatible with it thereby reducing its optical monitoring levels. The temperatures at which the two are at optimum activity also differ greatly between the two.


Cisco GLC-LH-SM is a transceiver manufactured by the Cisco unit of digital hardware that works as a combination of a transistor and receiver, hence the combination name transceiver.

It was one of the first generation of transceivers manufactured by the Cisco group that eventually faded out of the market. But there are still users who use the GLC-LH-SM version at homes or offices.

Cisco GLC-LH-SMD is another kind of transistor-receiver combination manufactured and marketed by the Cisco groups to help business outlets with the conversion of electric and optical signals to one another thereby creating a non-readable communication channel between multiple units.

This can be considered as the second generation of transistors released by Cisco. It is the more commonly used transceiver.

Comparison Table Between Cisco GLC-LH-SM and GLC-LH-SMD

Parameters of ComparisonCisco GLC-LH-SMCisco GLC-LH-SMD
DOM CompatibilityAbsentPresent
Optimum Operation Temperature0-70 degree C-5-85 degree C
Sale Ended in2013Not yet
Market ValueLessHigher in comparison
Is Storage ApplicableNoYes

What is Cisco GLC-LH-SM?

The transceiver gets its name from the transistor and receiver that is installed in the device.

GLC-LH-SM is a 1000BASE LX/LH small form of the originally designed device that had to be altered layer to fit the pocket size user-friendly device nature preferred by the users.

It is a factor plugged transportation module type manufactured by Cisco for MMF and SMF. Its connection portals include a dual connection method that is aligned with LC/ PC connectors.

This kind of connection is called a Duplex LC connector irrespective of the connection point. GLC-LH-SM has a standard 1310nm wavelength optimum for electric and optical signal recognition and transmission.

With a data transference rate of approximately 1 GB/s, it can cover a minimum distance of 10cm given the environmental conditions are favorable. Being a prototype model of the transceivers from Cisco, it doesn’t feature the DOM (digital optical monitoring).

DOM is used by transceivers with the hope to create an interface that would be able to access many optical parameters that prove helpful in digital as well as optical transmissions. This is a major drawback of the first generation of transceivers.

It’s generally compatible with all the later models released by Cisco and comes at a cheaper price. GLC-LH-SM when in use is in the need of model coupling to complete its required use.

The optimum temperature range for GLC-LH-SM to operate in all its glory is 0-70°C. Temperatures above or below this are considered to reduce the activity of the transceiver, therefore, rendering it useless.

The efficient voltage needed by GLC-LH-SM is around 3.3 volts and applies to the classic transceiver 1000BASE LX/LH Ethernet Or Gigabit Ethernet.

GLC-LH-SM transceivers stopped their market products in the year 2013. But there are still users who use it despite it going out of trend.

What is Cisco GLC-LH-SMD?

GLC-LH-SMD is the second generation of transceivers introduced by Cisco manufacturers. It is completely compliant with IEEE version code 802.3z that brings the transceiver under the BASE standard of 1000 LX.

Like all transceivers, it uses optical monitoring with digital elements that help in transferring the signal type from one to another. It has a staggering wavelength transmission of about 1300nm that can cover up to a distance of 10km.

The single-mode fiber (SMF) used in GLC-LH-SMD helps it gain a transmission reach of about 10km as compared to the 5km transmission capacity of a standard transceiver. The data transferring speed of GLC-LH-SMD can be as high as 1G.

Like almost all other transceivers with different versions available, even the GLC-LH-SMD has a duplex connector that comes in the LC model. The dual LC/PC connector ports that it is equipped with providing a huge advantage to the connection points.

Its major attractive and user-friendly element is its compatible nature with DOM that enhances its optical activities and digital reading capabilities. DOM is to create better additional support for optical monitoring.

It is compatible with most other transceivers that are available in the market from the Cisco manufacturers. Despite its good features and compatibility, it is rather expensive when compared to all other transceivers thereby keeping off buyers.

The operating temperature required by the GLC-LH-SMD is -5° – 85° C. Any temperature above or below reduces the functional aspects of the transceiver.

The transmitter in the transceiver uses a DFB laser service to transfer the optical signals converted to electrical ones. GLC-LH-SMD can be applied in many terms such as storage and IP networks along with the networks such as LAN, WAN, and MAN.

Main Differences Between Cisco GLC-LH-SM and GLC-LH-SMD

  1. While the optimum temperature at which GLC-LH-SMD can be operated starts from a negative value of -5°C to 85°C, the temperature required by GLC-LH-SM is comparatively less and ranges from 0-70°C.
  2. GLC-LH-SMD has an Ethernet BASE capability of 1000 LX whereas GLC-LH-SM has the BASE factor of 1000BASE LC.
  3. GLC-LH-SMD is still in use and of demand in the market up until this day but GLC-LH-SM had been cleared out of the markets and sales stopped as the manufacturing and brought down in 2013.
  4. GLC-LH-SM has no DOM compatibility, therefore, lacking advanced digital optical data monitoring. On the other hand, GLC-LH-SMD is DOM compatible and has an enhanced optical monitoring ability.
  5. The older version GLC-LH-SM is less expensive due to its lack of later technological features but GLC-LH-SMD is more expensive and sought after by the users due to its upgraded features.


There is barely much difference between the transceivers GLC-LH-SM and GLC-LH-SMD as their optimum function is the very same. Transceivers consist of transmitters and receivers that transmit optical signals by converting them into air transmittable electric signals.

These electric signals that are received by the receiver part of the transceiver are converted into a readable form that is optical signals. The temperature of operation is a huge differing factor that decides upon the functionality of the transceiver.

To enhance the properties withheld in GLC-LH-SMD, a coupled model conditioning patch would be required. Even though GLC-LH-SM has been out of the market for so long, some users prefer it over other new versions.


  1. http://citeseerx.ist.psu.edu/viewdoc/download?doi=
  2. https://www.theseus.fi/handle/10024/72128
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