Optical spectrum analyzers measure the optical power energy distribution over the wavelength domain thereby enabling spectral analyses and monitoring of optical signals and networks. OSAs have become a fundamental device in telecommunications. This is due to its involvement in several applications such as light source characterization, optical amplifier assessment, WDM network analysis and OSNR measurement. With respect to optical design, optical spectrum analyzers are divided into two categories. The first consists of devices for measuring optical power after the decomposition of the different wavelengths and frequencies. The second category includes high-resolution optical spectrum analyzers where spectral resolution under 1 pm is achievable.