High reflectivity superstructured FBG for coherent optical code generation and recognition

The performance of the phase-shifted superstructured fiber Bragg grating (SSFBG) for optical code (OC) recognition was investigated with different reflectivity as well as input pulse width. The auto-correlation peak (PA) and the ratios of PA to the maximum wing level (P/W) and cross-correlation level (P/C) were used to quantitatively evaluate the OC recognition performance. There is a conflict between obtaining high PA and high P/W and P/C ratios in high reflectivity regime. The approach of applying apodization technique to improve the performance in high reflectivity regime is proposed. The comparative experimental investigations with 127-chip 160-Gchip/s SSFBG are carried out to confirm the effectiveness of the proposed approach. Error-free transmission with multiplexing of two active users has been successfully achieved by the apodized SSFBG at a data rate of 1.25 Gbit/s.