In fact, these two is a thing, 1.25g optical module is 1g optical module.

First of all, we need to understand that g on behalf of the optical module transmission rate of gigabit, optical module unified standard transmission rate level to 155.520Mb / s for the basic rate, also known as stm-1.

We say that the transmission speed of the optical module is a multiple of this, for example: 1G optical module is actually 1.25G, that is, stm-8, i.e., 155.520 × 8 = 1244.16Mb/s.