During OTDR testing, pulses generated by the pulse generator drive the laser diode (LD) to emit light pulses. These pulses are directed into the fiber under test through a directional coupler. Scattering occurs within the fiber due to impurities and bubbles, with some of this backward scattering (BACK SCATTERINGLIGHT) combining with Fresnel reflections from irregular fiber end surfaces. The resulting light is reflected back to the coupler and captured by photodiodes, where it is converted into electrical waves. Given the extremely weak nature of this reflected light, it undergoes repeated transmission, collection, averaging, and amplification before being processed by the network management platform. This system features high dynamic range and superior resolution