What is the "light enters copper and retreats" in communication, and how is it progressing now?

Light entering copper means that most of the current cables are optical cables, and most of the past coaxial cables (with copper cores) have withdrawn from the historical stage. At present, the transmission speed of optical cable is more than 100 times that of coaxial cable. This change is revolutionary. At present, power transmission is still dominated by copper cables, which may be replaced by other means in the future.