G. 652 single mode fiber common single-mode fiber, is divided intoG.652A, G. 652B, G. 652C and G. 652D four subgroups, IEC and GB/TG.652C named B1.3 the rest is named B1.1
G.652A=G.652B=G. 652D=B1.1 G. 652C=B1.3A- a few people and C,now, B and D compatible with A and c, so now there are B andD, gradually are D, G.652B=B1.1, G.652D=B1.3 B1.1=B1
