A replaceable transmitting module is disposed on an optical connector. The replaceable transmitting module comprises a plurality of optical sub-assemblies disposed independently respectively, and at least one positioning mount disposed on the optical connector. The optical sub-assemblies comprises at least one edge-emitting laser diode, a second cover disposed on the edge-emitting laser diode, and a second lens disposed on the second cover and corresponding to the edge-emitting laser diode. The positioning mount comprises a base and a plurality of positioning portions which are disposed on the base and to fix the optical sub-assemblies, respectively.