This note teases through the relationship between SNR and Ber.
Optical signal to noise ratio (osnr), as the name suggests, is the ratio of signal to noise, the relationship is as follows,
OSNR is used to characterize the level of noise in the optical system, the smaller the noise, the larger the OSNR, as shown in the following figure,
(Image courtesy of https://mapyourtech.com/entries/general/osnr-what-does-this-mean-why-do-we-need-and-how-to-take-care-of-it-)
The so-called bit error rate (bit error rate) refers to the proportion of the number of errors in the communication system to the total number of codes transmitted, satisfying the following equation.
between osnr and ber satisfies an empirical formula,
The louder the system, the smaller the OSNR and the greater the BER.
Specifically, the bit error rate is the probability of recognizing 1 as 0 and 0 as 1. Suppose the level of noise is a Gaussian distribution, corresponding to the shaded area in the figure below,
Define q=(x1-x0)/(sigma_1 - sigma_0), assuming that the distribution of the signal satisfies the Gaussian distribution. After some deduction, it can be obtained,
The typical ber vs. q curve is shown in the figure below,
The q value can be obtained from the eye diagram.