This MIB module defines the managed objects for physical layer characteristics of DWDM optical channel interfaces and performance statistics objects for protocol specific error counters in DWDM optical devices. Performance monitoring (PM) parameters are used by service providers to gather, store, set thresholds for and report performance data for early detection of problems. Thresholds are used to set error levels for each PM parameter. During the accumulation cycle, if the current value of a performance monitoring parameter reaches or exceeds its corresponding threshold value, a threshold crossing alarm (TCA) is generated. The TCAs provide early detection of performance degradation. The definitions contained herein are based on the OTN specifications in ITU-T G.872[ITU-T G.872], G.709 [ITU-T G.709], G.798[ITU-T G.798], G.874[ITU-T G.874], and G.874.1[ITU-T G.874.1]. Glossary: OTN : Optical Transport Network (ITU-T G.709). FEC : Forward Error Correction. PM : Performance Monitor. DWDM : Dense Wavelength Division Multiplexing. FE : Farend or client side of the interface. NE : Nearend or trunk side of the interface. ADM : Add Drop Multiplexer. OCH : Optical Channel. OTS : Optical Transport Section. OMS : Optical Multiplex Section. TCA : Threshold Crossing Alarm. OSC : Optical Supervisory Channel. DCU : Dispersion Compensation Unit. EXP : Express Channel. OSNR : Optical singal to noise ratio. OTU : Optical Channel Transport Unit. ODU : Optical Channel Data Unit.