This application note proves the high efficiency of the Optical Complex Spectrum Analyzer AP2441B/AP2443B in measuring and testing any kind of usual modulation formats. Compared to a standard oscilloscope, the Optical Complex Spectrum Analyzer AP2441B/AP2443B has a maximum bandwidth > 6 THz due the complex spectral analysis principle giving access to the optical phase and intensity both in frequency and time domains. Therefore, the Optical Complex Spectrum Analyzer has no baud/bit rate limitations. Examples of RZ short pulses (2 ps pulse-width), pulse time resolved chirp, Differential Phase-Shift Keying (DPSK) modulation and Quadrature Phase-Shift Keying (QPSK) modulation measurements are presented.