High resolution optical spectrum analysis by coherent detection with multi-electrode DBR-LD´s as local oscillators

This paper proposes a novel high resolution optical spectrum analyzer based on the coherent detection technique wherein multi-electrode DBR-LD´s are used as local oscillators. A frequency resolution of 100 MHz with 4.2 nm wavelength scanning range centered at 1.551 μm is attained. The main advantage of this technique is that image signal rejection, which is indispensable in optical spectrum measurement using the heterodyne detection technique, is unnecessary. The wavelength resolution can be ultimately improved to the order of the linewidth of the local light source. We also demonstrate the measurement of the absolute wavelength by employing two Fabry-Perot etalons with different FSR´s to obtain an absolute wavelength accuracy of less than 1 GHz