While these two requirements are met in full by a few currently available AWGs, it is very difficult to find an AWG which can directly synthesize frequencies around the required center frequency of ~11GHz.

At the expense of halving the?sampling rate, this technique still maintains all the benefits of?its SA-BOTDA predecessor.

For the dynamic measurement, the??ν=70MHz (γ±=1), solid curve in Fig. 3, was chosen as a compromise between sensitivity (the slope of the?R?curve), the dynamic range and the measurement SNR, which is higher for lower values of?ν[13].

In general terms, the linewidth broadening observed agrees well with the results presented previously [7], hence independently demonstrating the existence of this effect.

Moreover, the demonstration is performed with a different type of BOTDA experimental setup, hence possible origins of the linewidth broadening effect due to unintended experimental conditions are less probable.

The multi-slope assisted F-BOTDA is a good candidate for real-time online monitoring system rather than a precise measuring.

As we analyzed in Section II, the polarization fading is almost eliminated by flipping the BLS and subtracting it by the BGS, which coincides with the results in [6,11].

The PC is employed at the input of each EOM to achieve maximum optical power at the ouput of the EOMs.