Abstract

One of the most important components in a WDM light transmission system is a wavelength multiplexer/demultiplexer. For a system in which the wavelength bandwidth is limited by the amplifier gain bandwidth or the fiber chromatic dispersion, a narrow channel spacing is required in multichannel WDM. Other requirements for a WDM filter are low insertion loss, low polarization dependent loss, broad transmission band in each channel, low crosstalk from the neighbor channels, and stability. One possible means for multi-channel, dense WDM filters is a diffraction grating. However, a reflection-type diffraction grating which has a blaze angle of ~30 degrees shows small angular-dispersion, which requires a long light path in a filter¹. The dispersion can be enhanced with a large blaze angle, and this enhancement was demonstrated by using transmission-type diffraction in a planar waveguide^2,3.

© 1996 Optical Society of America