Wavelength and code division multiplexing toward diffuse optical imaging

This work presents the latest simulations and experimental results of an innovative module for functional diffused optical imaging based on double encoding of wavelength and position of the emitting light. A spread spectrum approach to near infrared diffusive optical imaging is implemented: a pseudo-random sequence is used to modulate the light before entering a turbid medium; when the coded sequence propagates through the tissue, it is split into a group of components that have different path lengths. The correlation of the detected signals with the sequence can pick up each component with a specific delay, with the consequence of obtaining time domain information of arriving replicas. We propose to improve that approach, adopting a code division multiple access technology. A module which is expected to enhance the performances in terms of measured time and SNR is presented. We called this technique Wavelength and Space Code Division Multiplexing (WS-CDM).