In this paper, a new photoplethysmography (PPG) bio-sensing system is demonstrated to process higher-quality PPG signals. The proposed bio-sensing system contains four light-emitting diodes (LEDs) in wavelengths of 940, 850, 645, and 523 nm and two photodiodes (PDs). The enhanced biosensing performance is analyzed and designed by optical simulation based on Beer-Lambert law and optimized for maximizing the performance by prudent floor-planning of light transmitter and receiver.