Answer: OC level in SONET are analogous to the digital signal levels of T-carriers.
Explanation: Synchronous optical networking(SONET) is the protocols that helps in transmitting of data in large amount. It uses the OC level(optical carrier) in the asynchronous transfer mode for carrying the data signals .It is usually termed as similar to the digital signal level of T-carriers which carries the large data signal in digital form in complete digital transmission of signal.