This document describes how to check the switch interface or port status and how to locate an interface physically down fault and restore the interface to the up state. Hardware. Optical Transport Network (OTN) systems have several alarms to monitor network health and detect issues that could impact performance. In an optical network, alarm propagation defines how different alarms propagate in a larger link during any failure in the network. Even minor deviations—whether too high, too low, or unstable—can impact signal integrity, trigger service alarms, or interrupt traffic on DWDM, OTN, or long-haul optical line systems. Hardware failures: include hardware.
[pdf] An optical transport network (OTN) is a digital wrapper that encapsulates frames of data, to allow multiple data sources to be sent on the same channel. This creates an optical for each client signal. defines an optical transport network as a set of optical network elements (ONE) connected by links, able to provide functionality of transport, multiplexing.
[pdf] 
