Influence of external cavity length on lasing wavelength variation of fiber grating semiconductor laser with ambient temperature

After taking into account the phase contribution of fiber grating (FG) to the longitudinal mode formation of the fiber grating external cavity semiconductor laser (FGECSL) and starting from the threshold condition of the FGECSL, the effect of the external cavity length on the lasing wavelength variation of the FGECSL with ambient temperature has been investigated theoretically. The numerical simulations show that with the increase of temperature, the lasing wavelength has a common tendency shifting towards longer wavelengths for short or long external cavity; for a short external cavity, the shift is accompanied by a periodic mode hopping; and for a long external cavity, the shift is approximately linear. The theoretical results, which are in agreement with reported experimental observations, have been analyzed and explained.