In order to distinguish their optical modules,different manufacturers can distinguish them by their wavelength,transmission distance,package,etc.do you know any other methods?   　　Commonly used optical modules have four wavelengths,850nm,1310nm,1490nm and 1550nm.Among them,the pull ring color of the Gigabit SFP optical module 850nm is black,the pull ring color of 1310nm is blue,and...