Switch Market

Hi.
a modular switch is a device where you can insert hardware modules, and build it at your own design, using modules for you own needs.

a big advantage over fixed devices configuration, where the device is hardware limited to the physical ports it posses, not so scalable as a modular one.

First what is 1000base-LX & SX and what is fiber used for? My guess is for uplinking other switches but I really have no idea

Both are fibre technology used as you say for linking to other devices. Both a re Gigabit Ethernet over fibre but the LX transcievers can drive greater distances than the standard SX transcievers. For example, if you've got over legacy (62.5/125) fibre the maximum distance for Gigabit can be extended to 500 metres by using LX transcivers if you use a special mode-conditioning fibre patch lead as well. The actual distances supported depend on the type of fibre you've got installed; check out the Cisco website if you want the definitive info