Optical Fiber Communications 4th Edition by Gerd Keiser

Exercise 14

The uncertainty U of OTDR loss measure­ments as a function of the signal-to-noise ratio SNR can be approximated by 36
log| U |= 0.2SNR + 0.6
Here, U and SNR are given in decibels. If a 0.5-dB splice is located near the far end of a 50-km fiber, what dynamic range must the OTDR have to measure the insertion loss of this splice event with a ±0.05-dB accuracy. Assume the fiber attenuation is 0.33 dB/km.