Advanced design of the ultrahigh-channel-count fiber Bragg grating based on the double sampling method

A double sampling method enabling to have excellent channel uniformity and high in-band energy efficiency is firstly proposed for the design of an ultrahigh-channel-count fiber Bragg grating (FBG), which is based on the simultaneously utilization of an amplitude-assisted phase sampling (AAPS) function and a phase-only sampling (POS) function. As examples, two typical 10-dB FBGs with a length of 12 cm, dispersion of - 1360 ps/nm, channel spacing of 0.8 nm, and a consecutive 135- and 405- channels are numerically designed. The maximum index-modulations required are about 0.8x10(-3), and 1.3x10(-3), respectively. Compared with the proposed method, the other two kinds of double sampling schemes by utilizing either the double AAPS (i.e., AAPS+AAPS) or the double POS (i.e., POS+POS) have also been introduced for the design of the multichannel FBGs. Fabrication tolerances to the designed 135-channel FBG obtained with the AAPS plus POS method are numerically investigated.