How can a coherent laser single mode source be correctly coupled to a long length of multimode fiber and multimode receiver?

Most sources use single mode cables for single mode coherent lasers as connecting them to multimode cables can get quite complex and create compatibility issues. One of the issues associated with them is DMD or differential mode delay as singe mode launches into multimode fiber cable center which is somewhat uncertain. In case of lasers or devices with digital signals, there is, thankfully, a solution to this issue. Single mode fiber with an offset of about 15 microns can be coupled with offset launch cables.