A diffuse optical spectroscopic imaging (DOSI) apparatus for tissue spectroscopy measures absorption and scattering properties of tissue using multi-frequency frequency domain photon migration in a modular or networkable platform to provide full broadband information content. The apparatus includes: a broadband signal generator; a driver having an input coupled to the signal generator; a light source coupled to the driver, the light source for exposing the tissue to broadband modulated light at a plurality of wavelengths; an optical detector for receiving returned light from the tissue; an amplitude detection circuit communicated to the optical detector; a phase detection circuit communicated to the optical detector; and a plurality of filters and amplifiers, wherein the optical detector, amplitude detection circuit and phase detection circuit are interconnected with each other by corresponding ones of the plurality of filters and amplifiers to isolate signals and increase signal-to-noise ratio.