The LPDL 900/1100 series holographic diffraction gratings developed by Headwall Photonics Inc. of Fitchburg, Mass., have a frequency of 900 and 1100 grooves per millimeter and 90 to 95 percent efficiency in both the TM and TE polarizations, allowing for higher dispersion -- and therefore higher channel count -- in a more compact package.Used in telecommunications equipment, the gratings deliver low polarization-dependent loss -- less than 0.25 dB for each polarization when used near the Littrow angle -- enabling higher signal strength without the need for complex and expensive compensating elements. This performance requires original holographic gratings, which generate little stray light, greatly increasing the signal-to-noise ratio.A proprietary process generates a flat wavefront, allowing for a much larger clear aperture and thus a greater active surface. The gratings can be optimized for specific requirements by "tuning" parameters in the C- or L-bands or in both bands. Reliable and environmentally stable, they exceed the rigorous Telcordia GR-1221 standards for the telecommunications industry. One benefit of the LPDL is that users can build network products in a smaller footprint, with greater density and capacity, greater service life and a much lower cost of system ownership.