Performance comparison of 0/pi- and +/- pi/2-phase-shifted superstructured Fiber Bragg grating en/decoder

We compare the performances of the 0/pi-phase-shifted SSFBG (0/pi-SSFBG) and the +/- pi/2-phase-shifted SSFBG (+/- pi/2-SSFBG) en/decoders in the three aspects: the security, coding and system performances. In terms of the security performance, we evaluate the security performance by the investigation on the encoded waveform of both encoders. We also propose and demonstrate the code extraction technique for the +/- pi/2-SSFBG encoder when input pulse has large pulse width. Then, we analyze the coding performance of these two kinds of en/decoders by the calculation of autocorrelation and cross-correlation with sets of 31-chip, 63-chip and 127-chip Gold codes. Furthermore, we propose and demonstrate the hybrid use of both en/decoders. To demonstrate the performance of both en/decoders and the hybrid use in the different systems, we employ four 31-chip 640 Gchip/s 0/pi-SSFBG and +/- pi/2-SSFBG en/decoders in the 4-user 10 Gbps/user on-off keying and differential phase-shift keying OCDMA systems. (C) 2011 Optical Society of America