Improving the Performance of Fiber Gratings with Sinusoidal Chirps

Sinusoidal chirps are introduced in fiber gratings to improve their performance as dispersion compensators and multichannel filters. The sinusoidally chirped fiber gratings exhibit a flattop spectrum with steep edges and high reflectivity. The bandwidth utilization defined as the ratio of -1: -30-dB bandwidth could be very high ( >0.85). This structure can be applied to the sampled fiber gratings to enhance channel uniformity. We demonstrate 264 uniform channels with a 25-GHz-spacing for high-density-wavelength multiplexing applications. Multichannel dispersion compensations with seven uniform channels of 50-GHz-spacing in short fiber gratings are also demonstrated. The impact of possible fabrication errors on the spectra of the gratings is discussed.