Optical frequency combs (OFCs) are a revolutionary light source for numerous applications due to their precisely spaced coherent optical wavelengths. his paper will focus on OFCs for employment in next generation dense/ultra-dense wavelength division multiplexed high-speed optical communication systems, which places stringent requirements on the OFC. These requirements include stability, linewidth, cost-efficiency, power consumption and form-factor. Monolithically integrated comb sources with simple and compact designs offer many of these features. In this work, the authors present a gain switched integrated optical frequency comb source encased in a high-speed temperature controlled butterfly package. Experimental results on characterisation and its application to various optical transmission systems will be presented.