An　optimization-based　technique　for　high-channel-count　fiber　Bragg　grating　(FBG)　filter　synthesis　is　proposed.　The　approach　is　based　on　utilizing　a　tailored　group　delay　to　construct　a　mathematical　optimization　model.　In　the　objective　function,　both　the　maximum　index　modulation　and　the　dispersion　of　FBG　must　be　optimized　simultaneously.　An　effective　evolutionary　algorithm,　the　differential　evolution　(DE)　algorithm,　is　applied　to　find　the　optimal　group　delay　parameter.　Design　examples　demonstrate　that　the　proposed　approach　yields　a　remarkable　reduction　in　maximum　index　modulation　with　low　dispersion　in　each　channel.　©　2015　IOP　Publishing　Ltd.