Estimating the Properties of DWDM Filters Before Designing and Their Error Sensitivity and Compensation Effects in Production

It is practical to estimate the pass band width (BW) and blocking band width of a dense wavelength division multiplexing (DWDM) filter as a function of refractive indices, spacers, number of layer pairs, and number of cavities before designing the filter. This can be a practical design guide as to which parameters should be used to gain a desired result. The derivation and resulting formulas for these estimates are described and presented. The successful production of a final design then depends on the process stability, monitoring techniques, and related errors. The amazing error compensation capability of optical monitoring at the pass band wavelength is the major factor that makes the production of DWDM filters at all possible. The resulting performance is much more sensitive to errors in some layers of a design than others. We show errors that are redeemable and how that is accomplished.