pulses is hard to control certain embodiments of the invention use an fpi as a pulse replicator however unlike conventional approaches to using fpis certain embodiments of the invention use the fpi in reflection mode fpir the inventors have observed that an fpir behaves quite differently than an fpi in transmission mode and that the fpir may be arranged to create replicate a pulse and to obtain certain characteristics specifically fig4 shows an exemplary embodiment of the invention using an fpir input 402 receives optical pulses and transmits them to circulator 404 or equivalent device such as a coupler the circulator 404 transmits pulses received on input 402 to link 406 such pulses are then transmitted to fpir 408 as will be explained in more detail below fpir 408 will generate a replicated pulse from the received pulse the two pulses will then be sent on link 406 toward circulator 404 circulator 404 transmits signals received on link 406 to output 410 the inventors have observed that an fpir 408 with appropriate values of end reflectivity for the surfaces see e g 102 104 of fig1 can closely approximate a mi or mzi pulse replicator fig5 shows the frequency response 502 of a reflected signal of a preferred fpir 408 in which the first surface 102 to receive the input pulse has 17 mirror reflectivity and the second surface 104 has 24 mirror reflectivity fig5.