Question: what is the difference between stm 1 and stm 4?
Answer: STM-1 = 155.520 Mbit/s. STM-4 = 622.080 Mbit/s. STM-16 = 2,488.320 Mbit/s (~2.5 Gbit/s) STM-64 = 9,953.280 Mbit/s (~10 Gbit/s)