Theoretical analysis of supermode noise in mode-locked fiber laser with composite cavity

In order to study the supermode noise suppression in a mode-locked fiber laser with composite cavity,an effective structure model of the composite cavity was built based on the transfer function.The characteristic of an active modelocked ring fiber laser with composite cavity was investigated theoretically.The dependence of the effective basic frequency of the composite cavity on the length of two sub-cavities was demonstrated in detail.Setting the RF modulation frequency at 1 GHz,the relation between the supermode noise and parameters of the composite cavity were listed in a table.It was shown that the number of supermodes was reducedhowever,the reduction of overall supermode noise was not remarkable in comparison with the standard single-cavity configuration.The result is helpful for experimental study of supermode noise of active mode-locked ring fiber laser with composite cavity.