PONs	passive optical networks
BER	bit error rate
TWDM-PON	Time and Wavelength Division Multiplexed Passive Optical Network
MSE	Mean Squared Error
MAE	Mean Absolute Error
RMSE	Root Mean Squared Error
GBR	Gradient Boosting Regression
MLP	Multi-Layer Perceptron
R2	coefficient of determination
QoT	Quality of Transmission
SVR	Support Vector Regression
LR	Linear Regression
RF	Random Forest Regression
D/S	Downstream direction
U/S	Upstream direction
BtB	back-to-back
NN	Neural Networks
DL	Deep learning
ML	Machine learning
(NG)-PON2	Next-Generation Passive Optical Network Stage 2
IEEE	Institute of Electrical and Electronics Engineers
ITU-T	International Telecommunication Union
FBG	Fiber Bragg Grating
EDFA	Erbium Doped Fiber Amplifier
IoT	Internet of Things