The effect of Lensing on apondized Fiber Bragg Gratings

Fiber bragg grating is an in fiber optical passive device used in communication and sensing applications. It is a band rejection filter used to reflect back a band the  optical spectrum and allow the rest of the signal to pass through. This is an important filter device in optical communication networks and sidelobes should be as small as possible. Typical approaches in Minimizing the side lobes of the fiber bragg gratings (GBG) is using apodized refractive index profile like Gaussian or Raised Cosine distributions. Apodization does only affect the side lobes of the fiber bragg gratings but also the reflectivity and bandwidth. Fiber bragg grating is used as a filter in laser source fabrication to improve the quality of the beam by reflecting back into the laser small amount of power at the required bandwidth. This stabilize the wavelength and lock it to the specific value required. Lensed terminal fiber bragg grating is required to improve the coupling efficiency of the output power from the laser diode into the fiber and reduce the reflections back to the diode. In this project, we will study the effect of lensing using thermal etching technique on the apodization profile and side lobe suppression ratio of fiber bragg grating as its performance parameter.