Figure 4. Decrease of total capacity C_TOT due to noise, for an ESN with ρ = 0.95, for different values of ι, corresponding to varying degree of nonlinearity.

In the left panel there are two i.i.d. inputs, the signal u and the noise v. The horizontal axis is the input signal to noise ratio in dB (). The fraction of the total capacity which is usable increases when the SNR increases, and decreases when the system becomes more non-linear (increasing ι). In the right panel there are a varying number K of i.i.d. inputs with equal power, the total power being kept constant as K varies. The capacity for computing functions of a single input in the presence of multiple inputs is plotted. The black line indicates the situation for a strictly linear system, where the capacity for a single input should equal N/K.