Superstructured FBG based optical encoder/decoder for highly-confidential 40 Gbps telecommunication network

40 Gbps optical encoding/decoding is demonstrated utilizing 8-level phase codes, 8 grating chips and 2.6 mm long superstructured fiber Bragg grating (SSFBG). Novel refractive index profile is applied to the SSFBG to obtain highlyrecognizable performance of encoding signal and highly-confidential decoding signal. Time-spreading optical codes are clearly observed from the encoding signals, and over 13 dB power contrast ratio is confirmed from the decoding signals.