Distributed feedback fiber laser (DFB-FL) is a kind of laser consisting of a single phase shifted fiber grating directly writing in the rare earth doped fiber, depending on the narrow bandwidth, low noise, and stable single-mode operation. In this project, CGCRI developed intrinsically photosensitive erbium doped fiber having ultra high NA ( ~0.30) with low core diameter (~ 3.0 micron ). An measured refractive index profile along the diameter of the fiber cross section is shown in Fig.1. CGCRI also developed DFB-FL having output power of more than 60.0 µW @100 mw pump power at 980nm along backward direction with low threshold pump power of 5.0 mW. The phase shifted grating needed to produce the fiber laser was inscribed at CGCRI. Fig 2 shows the spectral characteristics of the fiber laser where as the variation of the output laser power as a function of pump power is shown in Fig.3. The phase noise of developed DFB-FL tested by NPOL, Kochi at 1 KHz was found to be -110dB V/ rt. Hz. This corresponds to a frequency noise of about 100Hz/rt.Hz. These DFB-FL will be used for development of optical hydrophone.
FBG based distributed feedback laser for sensor applications
