What is the difference between LH and LX

The difference between LX and LH SFP modules. Long Haul ( LH ) denotes longer distances while Long Wavelength ( LX ) denotes less energy which is obviously shorter distance. Why does Cisco use both LX and LH for certain SFP modules?

Do they denote the capability of the module to work both for MM ( which will be Long wavelength ) and SM ( Long Haul ) fiber?

What does it infer if a modules says like "Cisco 1000BASE-LX/LH SFP" ?

Generally a module is either made for single mode (More distance) / multi-mode (short distance). 

If used with SM fiber it can go upto 10Km

It used with MM it can go upto 550meters (depend on what kind os MM fiber you have) You need a mode conditioning patch chord too with legacy MM i think OM1 and 2.

Read this link and don't worry about LX/LH (You will get the distance mentioned above depending on the type of fiber you are using)

http://en.wikipedia.org/wiki/Gigabit_Ethernet

Before it was standardized 1000BASE-LX10 was essentially already in widespread use by many vendors as a proprietary extension called either 1000BASE-LX/LH or 1000BASE-LH

• GLC-SX-MM (1000BASE-SX) SFP modules that provide a 1000 Mb/s wired connection to a network through an 850nM (SX) fiber-optic link using an LC physical connector. 1000BASE-SX SFP for Multimode Fiber Only
  The 1000BASE-SX SFP, compatible with the IEEE 802.3z 1000BASE-SX standard, operates on legacy 50 μm multimode fiber links up to 550 m and on 62.5 μm Fiber Distributed Data Interface (FDDI)-grade multimode fibers up to 220 m. It can support up to 1km over laser-optimized 50 μm multimode fiber cable.
• GLC-LH-SM (1000BASE-LX) SFP modules that provide a 1000 Mb/s wired connection to a network through a 1300nM (LX/LH) fiber-optic link using an LC physical connector. 1000BASE-LX/LH SFP for Both Multimode and Single-Mode Fibers. Cisco 1000BASE-LX/LH SFP transceiver module for SMF and MMF, 1300-nm wavelength, commercial operating temperature range, 32°F to 158°F (0°C to 70°C)
• GLC-T (1000BASE-T) SFP modules that provide a 1000 Mb/s wired connection to a network through a copper link using an RJ-45 physical connector.

http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/product_bulletin_c25-681353.html

Product ID Consolidation

Legacy Product ID		New Product ID	New Product ID Target First Customer Ship Date
GLC-SX-MM	SFP-GE-S	GLC-SX-MMD	August 2011
GLC-LH-SM	SFP-GE-L	GLC-LH-SMD	August 2011
GLC-ZX-SM	SFP-GE-Z	GLC-ZX-SMD	January 2013
GLC-T	SFP-GE-T	GLC-TE	TBD