Choose a very right Cisco Transceiver Module or a Optical Transceivers for your Cisco equipment from router-switch.com, such as Cisco GBIC, SFP GLC module, X2 Module and OADM/EWDM Module.  Like the move from GBIC to SFP,  the move from XENPAK to SFP+ seems inevitable, but currently there are four standard modules/form-factors available.  SFP: also called mini-GBIC, is upgraded version of GBIC transceiver. SFP+: a 10GbE optics using the same physical form factor as a gigabit SFP. Because of this, many of the small SFP+ based 10GbE switches use 1G/10G ports, giving an added degree of flexibility.  There are more popular Cisco SFP transceiver modules you can select from router-switch.com, including GLC-SX-MMD, GLC-LH-SMD, GLC-T, SFP-10G-SR, etc. And you can enjoy the best price, flexible and professional services while purchasing the main SFP, SFP+, GBIC modules and other Transceivers. It will offer you a good warranty and more free CCIE technical support.