The statement that WT uses a unique identifier based on a pair of numbers encoded by Optical Transponders (OTs) into each service wavelength direction is TRUE. WT is a feature of the 1830 PSS that allows for automatic identification and tracking of wavelengths across different network elements and domains. WT uses Wave Keys, which are unique identifiers composed of two numbers: a Wave Key ID and a Wave Key Code. The Wave Key ID identifies the OT that generates the wavelength, while the Wave Key Code identifies the wavelength itself within a given OT6. The Wave Keys are encoded by OTs into each service wavelength direction using phase modulation, and can be decoded by other OTs or amplifiers that have WT capability. WT enables various applications and benefits, such as simplified commissioning, automated wavelength routing, enhanced fault localization, and improved network security. References : Nokia Optical Diagnostics and Troubleshooting Course | Nokia, Optical User Guide - Nokia, Alcatel-Lucent 1830 PSS-8 and PSS-16 Photonic Service Switch