Widely tunable external cavity semiconductor lasers with sampled fiber gratings are investigated. Their static properties,
such as threshold gain, tuning characteristic, emitting light spectrum, and side mode suppression ratio, have been
simulated and discussed by a combined theoretical model, which is developed to match experimental results. Up to
thirteen tunable channels can be obtained in this laser with high side-mode suppression ratios by tuning the injection
current of the passive phase control section. With the decrease of AR-coating reflectivity, the narrow line-widths, wide
tuning range, and high threshold gain in those tunable external cavity semiconductor lasers have been presented.