Experimental study of supermode noise of harmonically mode-locked erbium-doped fibre lasers with composite cavity

An experimental study of supermode noise of harmonically actively mode-locked erbium-doped fibre lasers in the composite-cavity configuration is reported. Our study shows that the number of supermodes is reduced, as expected. However, this reduction is by far less efficient than what was previously reported. In particular. we found in measured RF spectra that supermodes appear in wide periodic frequency windows. Our most significant result is that. contrary to what has been previously reported. we did not measure in the composite-cavity laser any significant reduction of the overall supermode noise in comparison with the standard single-cavity configuration. (C) 2002 Elsevier Science B.V. All rights reserved.