Measure insertion loss and return loss after installation (visual fault locator, OTDR or power meter tests) to confirm that bends haven't created excess loss before commissioning. Bend-insensitive fiber is engineered to balance flexibility and optical performance. When stressed by bending, light in the outer part of the core is no longer guided in the core of the fiber so some is lost, coupled from the core into the cladding, creating a higher loss in the stressed section of the fiber. If you put a. Bend losses are a frequently encountered problem in the context of waveguides, and in particular in fiber optics, since fibers can be easily bent. 657 optical fibers, which are designed for improved bending loss performance compared to ITU-T G.