Numerical study of 10 cm chirped fibre grating pairs for dispersion compensation at 10 Gbit/s over 600 km of non-dispersion shifted fibre

Much of the installed standard optical fibre for telecommunications systems has a low dispersion at wavelengths in the 1300 nn region. Upgrading to higher bit rates using Er-doped fibre amplifiers operating around 1550 nm wavelength is attractive, but, the fibre dispersion at these wavelengths then severely limits the transmission distance unless dispersion compensation is used. Chirped fibre Bragg gratings used as dispersion compensators have received considerable attention. Numerical studies are presented which show that to compensate for the dispersion due to 600-710 km of non-dispersion shifted fibre at 10 Gbit/s, a pair of 50% reflectivity gratings gives both better performance and a greater tolerance to apodisation and bandwidth than 95% reflectivity gratings. Apodisation is important for reducing pattern dependency. The effects of fibre nonlinearity allow the system length to be extended by ≈60 km. Gratings positioned at 200 and 400 km provided the lowest penalty and greatest tolerance to the distance of the combinations investigated