[en] We present an optical all-fibre data acquisition trigger signal particularly suited for fibre-laser asynchronous optical sampling systems. We demonstrate that in the case where the laser spectra are inadequately matched and deliver a weak interferometric signal, post electronic filtering can significantly enhance the signal, removing the necessity for optical band-pass filtering. The method requires no free-space optics and no precise alignment of focused beam spots, eliminating beam pointing stability and walk-off issues. (paper)