What's difference between the SFP and SFP +?

A lot of people don't know the difference between the SFP and SFP +, so it is sometimes bring unnecessary trouble. 10 g module has experienced from 300 pin, XENPAK, X2, the development of XFP, finally achieved to use and the size of the SFP as 10 g of signal transmission, that is the SFP +. SFP with its miniaturization, low-cost advantages of full enough equipment optical module of high demand, standard introduced in 2002, to 2010 displaced XFP as 10 g market mainstream.