Low-loss flat-top 50-GHz DWDM and ADD/DROP modules using all-fiber fourier filters

摘要

While DWDM is being widely deployed in the modern optical telecommunication systems, increasing the channel counts is a major continuing effort to create an even larger traffic bandwidth. While extending the communication window to the S and L bands is an option, the most common approach is to decrease the wavelength spacing between channels. However, when the channel spacing reaches less than 100-GHz, the current most successful DWDM technologies, namely dielectric thin-film filters and array waveguides, become too difficult and costly to implement. Although several alternative technologies, such as Fabry-Perot filters, diffraction gratings, and unbalanced Mach-Zehnder interferometers (1), can achieve very narrow channel separations, they suffer the disadvantage of having narrow Gaussian spectral responses within the channel passband, which is detrimental for high transmission rates. In this Paper, we demonstrate a flat-top DWDM interleaver using an all-fiber approach based on Fourier expansion technique, which enables extremely low insertion loss, polarization dependent loss, dispersion, and high isolation within the channel passbands.