Ultrahigh‐resolution coherent optical spectrum analysis based on electrical frequency sweeping with a doubled measurement range

Based on electrical frequency sweeping, an ultrahigh‐resolution coherent optical spectrum analyser with a doubled measurement range is proposed and experimentally demonstrated. In the scheme, a frequency‐swept electrical signal is converted to the optical domain. By selecting one of the second‐order sidebands of the generated optical signal, a wavelength‐swept signal with a frequency range that is twice the bandwidths of the electro‐optic and RF components is generated. With the wavelength‐swept signal, high‐resolution optical spectrum analysis with a doubled measurement range is implemented. In a proof‐of‐concept experiment, the spectrum of a multi‐tone optical signal with a bandwidth of 20 GHz is measured with a resolution of 1.5 MHz by employing 10 GHz components.