In this report a model of a tunable narrow linewidth laser used for telecommunications is presented. The model uses both theoretical analysis and experimental data to create the mathematical models governing its behaviour and is aimed to be useful in a development environment with requirements on accuracy, efficient implementation and adaptability to future design. Results show that the model presented achieves high accuracy in both optical and electrical measurements. In summary the model could be useful in a development environment with further improvements in adaptability possible in the future.