Measured in decibels (dB), return loss is calculated by comparing the input (or incident) power to the reflected power using the following formula: Return Loss = 10*log (incident power/reflected power) in +dB The result is always a positive number, and a higher value is better. The term Reflectance describes a single reflection in an optical assembly. Typically, Return. y. An optical connector is capable of frequent reconnections. Fiber connections, except fusio splices, are classified into two types of connection states. Insertion Loss (IL) is the amount of optical power lost as the signal travels from one point to another in a fiber optic link, usually across connectors or splices. Formula for. Return loss is the ratio of signal power injected from a source compared to the amount that is returned or reflected back toward the source. It is a critical performance parameter in both copper twisted pair and fiber optic cabling systems, because it can interfere with the transmitted signal and. How are coupling losses calculated for single-mode fibers? What is the effect of core size mismatch on coupling losses? How does angular mismatch affect single-mode fiber coupling losses? Why are coupling losses mode-dependent in multimode fibers? How does core size mismatch influence coupling.