Wavelength accuracy in WDM: techniques and standards for component characterization

Summary form only given. There are a variety of convenient wavelength calibration standards in the 1500 nm region, and other standards are under development for the WDM L-band. Fundamental references based on atomic and molecular absorption or emission lines provide the highest accuracy, but they are not available in all wavelength regions. Wavelength division multiplexing will likely expand into the 1300 and 1400 nm regions, and it will be very difficult to find absolute references for this wide wavelength range. Artifacts such as etalons or fiber Bragg gratings can provide references at arbitrary wavelengths, but they can suffer from large sensitivity to temperature, strain, and pressure. Passive or active thermal stabilization can substantially reduce this variability but the artifact references need to be checked periodically against a fundamental reference. Further in the future, stabilized frequency combs may become commercially available to provide frequency (wavelength) markers throughout the WDM regions.