High-Resolution Optical Vector Analysis With Enhanced Sensitivity

High-resolution and high-sensitivity optical vector analysis (OVA) is highly desired by many applications, such as optical sensors and photonic integrated circuits (PICs). However, it is difficult to achieve high resolution and high sensitivity simultaneously. Here, we propose and experimentally demonstrate a high sensitivity OVA using coherent detection to achieve the complex frequency responses (including magnitude and phase responses) of a device under test (DUT). Carrier phase noise (CPN) cancellation is employed to eliminate the carrier phase fluctuation induced by the coherent detection. In an experiment, the frequency responses of a fiber Bragg grating (FBG) is accurately measured by the proposed method when the probe light is suppressed by ~18 dB. As a comparison, the method using coherent detection without CPN cancellation can only achieve the magnitude response, and the method using direct detection cannot obtain an effective measurement. The influence of the linewidth and time delay on the measurement is discussed. The proposed OVA provides a stable, high resolution, high sensitivity and low cost approach for characterizing optical devices with arbitrary response, especially for optical devices with large loss or bandpass response.