Ultrabroad Brillouin instantaneous frequency measurement with a designed linear system response

We demonstrate an ultrabroad instantaneous frequency measurement (IFM) based on stimulated Brillouin scattering (SBS) with a designed linear system response. The linear system response is found to be the key factor that broadens the system bandwidth. It is realized by designing the sweeping method of frequency and amplitude of the local pump signal. With the improvement of linearity, the measurement error is decreased and the bandwidth of the SBS-based IFM is consequently enlarged. A Costas frequency modulated signal with an instantaneous bandwidth of 10.5 GHz is successfully measured by the designed system response. Further optimization of pump signal's characteristics extends the system bandwidth to 14.5 GHz. The measurement error of a linear frequency modulated (LFM) signal ranging from 6 GHz to 20.5 GHz is less than 1% of the instantaneous bandwidth.