I think you have it. I do remember carefully cutting braid also. That is likely your power plug. The fiber loop you mention, probably a rectangular plastic coupler that aligns two separate cables so the light circuit is completed. You would unclip both cables and insert into the CDC. You will see more of these in trunk under driver side hinge for the factory in adding sat radio and HD tuners...
2007 650i 0440/LCGE, 6MT, Sport, Nav, HUD, NiVi (w pin swap in CIC), DIRAC 752 Individual Audio retrofit (amp, speakers, coding), HD Radio (from CIC), CDC, SiriusXM. Coding: delete lawyer screen (CIC), fan speed LED seen on "auto" (with an LCI-IHKA), turn signals in HUD (CIC), personalized car ID for BT etc... Complete: CIC.C1A retrofit>E90.SSD >E90-E60 merged CIC.trc >CMEDIAR.C05 coded Combox, w/ ConnectedDrive, Plug-In, etc.