Method and apparatus are provided for a silicon substrate optical system for use in an interferometric fiber optic gyroscope (IFOG). A silicon substrate of the silicon substrate optical system is etched to receive optical components, including an input optical fiber, a pump source, a wavelength division multiplier, an isolator, a polarizing isolator, a beam splitting device, a PM tap coupler, a relative intensity noise (RIN) photodiode, a system photodiode, and an output optical fiber. The optical components are mounted on a silicon substrate to reduce the size and cost of the IFOG and increase reliability.