High energy electromagnetic radiation or heavy charged particles are extensively used for medical treatment of certain cancers. Precise prediction or measurements of energy deposition of any types of radiation on tissue is critical in radiation therapy. In this research, the sensitivity of optical fiber dosimeters specifically doped with phosphor (P), Germanium (Ge) and Erbium (Er) are analyzed using Co-60 source at 169 cGy/min. The sensors are calibrated and the values of radiation induced attenuation (RIA) are evaluated at different temperatures. Nondestructive method of laser bleaching is shown superior to thermal bleaching for sensor recovery. The error in P- doped and Er- doped fiber sensors are estimated to be 6 and 4%, respectively. The fastest recovery is assigned to Er- doped fiber. The results show that Er- doped optical fiber sensor can perform ultrahigh sensitive low dosimetry of gamma- ray for medical application. The results of the present work can provide implications for further enhancement of radiation sensing for real- time dosimetry.