Laser based additive manufacturing processes are becoming an increasingly popular tool for producing complex components and assemblies. During this process material is fused in a layer by layer approach to produce as-built components.  The use of a high energy laser to fuse material results in the formation of a laser induced plasma plume near the processing zone. Measuring the spectral emissions from this plasma is an emerging method for monitoring the quality of the fusion process. In this paper an optical emission sensing system is introduced to utilize the existing optical train of a commercial additive manufacturing system to measure Cr I emission relative to background emissions. Further, a calibration system is introduced to provide a means for capturing variations in spectral intensity across the build surface. Data collection on spectral intensity variation in relation to position allows for the creation of a position based correction factor. This enables more accurate spectral emission data collection and analysis. In addition to spectral based calibration, the calibration system is equipped to monitor shielding gas airspeed across the build surface. This proposed sensing and calibration system provides a means for accurate, real time process monitoring and serves as a valuable, independent quality assurance tool for in-situ monitoring of powder bed fusion build quality.