For real numbers, expect 2. 20 dB/km or better at 1550 nm for typical single-mode fiber if the manufacturer's specs check out. This calculator helps you estimate the total attenuation (signal loss) in a fiber optic cable link. Here are the details and instructions about each field and how they contribute to the calculation: 1. Loss per unit length of the fiber (e. The FBB Calculator is a simple yet powerful online tool that calculates the total fiber optic link loss (in decibels, dB) by factoring in losses caused by: By entering these values, users can instantly determine the total loss for a fiber optic link, enabling better system design, troubleshooting. Compute total signal attenuation (dB) for free space path loss or transmission lines (coaxial, twisted pair). distance with real-time graphing.