Frequency domain functional near infrared spectroscopy (FD-fNIRS) is a tissue optical measurement technique used to measure absolute haemoglobin concentrations in brain tissue. This work is intended to be the first step in the development of a wearable, low-cost FD-fNIRS device for neurofeedback applications. The system requirements were generated from a review of relevant literature. A simplified system architecturewas developed based on the various instrumentation methodologies proposed by various authors. The functional blocks of this system were prototyped and their performance was evaluated. The developed vertical-cavity surface-emitting laser (VCSEL) current source was found to have a span of 10uA which meets the design specifications. Challenges exist in optimally biasing silicon photomultiplier (SiPM), which is susceptible to optical and electronic noise sources.