Semiconductor laser optical amplifiers offer the possibility of simultaneous amplification of several signals in a multichannel coherent optical transmission system . However, to take full advantage of this possibility the optical amplifiers must be broadband (travelling wave amplifiers). In this paper we report on two channel transmission experiments in a 560 Mbit/s DPSK transmission system at 1,3 μm with use of two cascaded in-line optical amplifiers having a 3 dB bandwidth of more than 4 THz. In previous experiments with cascaded inline optical amplifiers the bandwidth of the optical amplifiers was much narrower, for instance 15 GHz . The aim of ' the present experiments is the investigation of crosstalk and of problems arrising from cascaded broadband in-line optical amplifiers.
© 1988 Optical Society of AmericaPDF Article