The optimization of Mach-Zehnder(MZ) filter based on concatenated long-period fiber gratings(LPFGs) is carried out by using the transfer matrix method,in order to increase the effective bandwidth and channel number.Several M-Z filters were manufactured for comparison.The research shows that the effective bandwidth and channel number of the M-Z filters have a close relation with the transmission minimum of a single LPFG and can be used for optimization.It has been found that the effective bandwid...