When the loopback method is used, the objects to be replaced can be optical fibers,...

When using the loopback method for troubleshooting or testing, the objects to be looped back or replaced can include optical fibers, boards, fiber adapters, optical attenuators, or power supply devices. Loopback tests help isolate faults by looping signals back to the source or intermediate points, enabling precise fault location. HCIP-Transmission explains that loopback can be applied at various points within the transmission system to verify signal integrity and component function, making it a versatile diagnostic tool in optical networks.