SENSITIVITY EVALUATION OF OPTICAL WIRELESS PPM SYSTEMS UTILIZING PIN-BJT RECEIVERS

A new hybrid optical wireless system based on pulse position modulatio n (PPM) and PIN-BJT receivers is proposed and its performance is evalu ated. The system is operated at a bit rate of 10 Mbit/s and lambda = 0 .85 mu m. The receiver achieves a low noise current of similar to 2.7 pA/root Hz. Original results are presented demonstrating that the syst em can achieve a sensitivity of -50.5 dBm at an error rate of 10(-9). This represents a sensitivity improvement of 9.8 dB over a comparable on-off keying (OOK) PIN-BJT system. The sensitivity enhancement has a significant impact on the optical wireless network, where the maximum allowed transmitted power is limited by safety issues. Moreover, the u se of PPM offers other advantages, such as the low average power which is suited for battery operation and a high peak power that aids detec tion.