The transmission matrix theory is used to calculate the reflection spectra of the sampled grating distributed Bragg reflector(SG-DBR) and that integrated with a semiconductor optical amplifier(SOA) which has output facets.The influence of the output facets reflection on the sampled grating DBR lasers with and without integrated SOA is investigated by the calculation.It is shown that the reflection peak of the sampled grating will split to two or even more peaks and the sub-peak may exceed the main peak by t...