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By optimizing the fabrication process of the chirped optical fiber Bragg grating (CFBG), some key problems of CFBG are solved, such as fabrication repetition, temperature stability, group delay ripple (GDR), fluctuation of the reflection spectrum, polarization mode dispersion (PMD), interaction of cascaded CFBG, and so on. The CFBG we fabricated can attain a temperature coefficient less than 0.0005 nm/°C, and the smoothed GDR and the fluctuation of the reflection spectrum are smaller than 10 ps and 0.5 dB, respectively. The PMD of each CFBG is less than 1 ps and the dispersion of each grating is larger than −2600 ps/(nm·km). With dispersion compensated by the CFBGs we fabricated, a 13 ´10 Gbit/s 3100 km ultra long G.652 fiber transmission system is successfully implemented without electric regenerator. The bit error rate (BER) of the system is below 10−4 without forward error correction (FEC); when FEC is added, the BER is below 10−12. The power penalty of the carrier-suppressed return-to-zero (CSRZ) code transmission system is only 2.5 dB. |
