In this intelligent fault detecting system in an optical fibre used to find the fault in optic fibre line. To design a fault monitoring module and find the fault in the line says across the customer sides. The idea behind this module is to monitor the received power supply in optical fibre using a Microcontroller. Laser output power monitoring circuit is designed using ISIS simulator to monitor the received power supply in the optical fibre. If there is any abrupt changes in power of optical line the automatic message will be transmitted to monitoring person regarding the fault in fibre via of GSM. Here we can operate Microcontroller in low power mode (sleep mode) to save power consumption. Automatic message is transmitted to monitoring person about the fault in optical line.