The RGD of the chirped grating was determined by various phase-shift techniques.
NIST also employed a new, low-coherence interferometer method to determine the RGD of the chirped grating.
From the RGD data, the linear slope of the chirped grating was determined from data within the -3 dB reflectance bandwidth (determined from a robust method described in Appendix F) using a least-squares fit.
In this section a history of the center wavelength of each of the telecom gratings and the linear slope of the RGD of the chirped grating is given as a function of time.
Figure 8 shows the - 3 dB center wavelength versus time for the telecom chirped grating.
Figure 9 shows the RGD linear slope history of the telecom chirped grating versus time in days.
From the relative reflectance of the chirped grating, the center wavelength and bandwidth were found at - 3 dB, and the minimum relative transmittance was determined from the relative transmittance data.
The data sets for the chirped grating are shown in Appendix C, Figs.
Figure 14 shows the -3 dB center wavelength measurement for the chirped grating.
Figure 16 shows the minimum relative transmittance of the chirped grating determined from the data shown in Appendix C, Fig.
Chirped gratings with larger RGD linear slopes will have larger RGD ripple amplitudes, increasing the need for more precision in RGD ripple measurements for WDM systems.
The measured RGD linear slope of the chirped grating had a range of 16 % when only one direction of the grating was measured.
Conventional modulators such as intrinsically chirped single-drive z-cut modulators have the potential for uncompensated signal transmission only up to 80 to 100 kilometers.
Besides outstanding zero-chirp modulators, the portfolio includes chirped modulators for different reaches that outperform competitor's z-cut modulators in conventional applications up to 100 kilometers and even extend the reach to 120 kilometers.