Gratings are the component of choice for telecommunication passive components since they offer high efficiency over a broad range of wavelengths, or channels, and, therefore, only one component is required for wavelength separation independent of the number of channels. This helps in product evolution since the same basic design platform can be modified as products are adapted to accommodate more channels.
Gratings can be replicated onto zero thermal expansion substrates so that their performance is independent of temperature. Array waveguides need to be actively heated for use and many other approaches to multiplexing are susceptible to performance changes resulting from temperature fluctuations. Newport's Richardson Gratings have been tested fully in accordance with Telcordia General Requirements 1221. We have gone through a very thorough test protocol and a report is available on request.
The most important features of a grating for use in a telecommunications application are the following.
Dispersion
Dispersion largely affects the size of the WDM component. The space taken up by a WDM component adds a substantial amount to the total cost in the fiber optic telecommunications industry. Higher dispersion often leads to smaller, more compact component design. Therefore, we offer high dispersion solutions such as our 1100–1200 g/mm gratings and our prism-buried gratings, which take advantage of the additional dispersion offered by a prism. Larger dispersion can also be combined with a wider grating to optimize resolution, a vital feature as channels become more densely packed into a given band (S-, C-, or L-band).
Low PDL
Polarization dependent loss must be minimized in fiber optic telecommunications so as to maintain the phase of the signal being carried. To meet this demand, Newport's Richardson Gratings offers a variety of low PDL gratings at groove frequencies from 600–1100 g/mm. Our master #1198, a 600 g/mm grating, provides phenomenal performance over the entire C-Band with 85% average efficiency. Master #3023, a 900 g/mm equivalent grating, offers low PDL in the C-Band with an efficiency averaging 80%. We also have buried options where the efficiency curve can be shifted by use of a high index material thus taking advantage of gratings with higher groove frequencies. Echelle gratings also offer the user excellent PDL performance at high dispersions due to the coalescence of S and P-plane efficiency curves in higher diffraction orders.
Low Loss
Newport's Richarson Gratings provide extremely high efficiency gold coated gratings that can be used when systems have other components to compensate for PDL. Efficiencies of these gratings approaches the theoretical maximum efficiency for a given groove frequency and wavelength range.
Testing
All of our gratings are made to the highest standards. We offer consistent wavefront performance on all products, meeting the tightest optical specifications. We inspect 100% of our gratings for cosmetic quality.
