How can we manage power (voltage ) loss in the long distance if elcetricity is fed along with the cable?
Fiber optical cable and electrical power ? They are not related.
The repeaters use copper wire bundled together with the fiber optic to power the repeaters, the voltage drop is managed with an engineered choice of voltage and current. Each cable has a different combination to suite the particular distance. And each cable would be tailored for the individual application.
