Both thanks to their capability to operate as multifunctional devices, their compatibility with numerous optical passive or active devices and their potentially low cost, Semiconductor Optical Amplifiers (SOAs) have demonstrated their attractiveness for lightwave communication systems and future integrated photonic circuits. In this context, we have studied in detail their photodetection functionality. The photodetection realization is very attractive with a SOA since it can be achieved in-line, in the amplification regime enabling good responsivity and without optical withdrawal. In this paper, we report our latest results about the in-line photodetection performances of Multielectrode SOAs (MSOAs), showing that they can be of great usefulness to optimize the reception and to perform fast in-line photodetection. The dynamic measurement experimental results, obtained by using a bielectrode SOA (300μm-200μm) and by detecting on its rear contact, show a bandwidth of about 1,2GHz which gives an idea of MSOAs potentiality. The latter has been investigated in this work by simulation especially for the long MSOAs and the results reveal that the bandwidth can significantly be enhanced, by simultaneously increasing the SOA total length and reducing the detection contact length, allowing a high speed photodetection on a wide band of frequency of about 7GHz centered on 4GHz with a 2mm long component having a 100μm rear contact length.