815.03 - Interferometry and Polarimetry Project

TECHNICAL STRATEGY

In general, we approach optical fiber and component metrology needs through the development of high-resolution measurement techniques and rigorous uncertainty analysis. Transfer of this metrology comes through publication of our measurement techniques, distribution of artifact standards, measurement comparisons and formal and informal calibrations of customer devices

Chromatic Dispersion

Our 2 GHz modulation phase shift system is available for measurement of chromatic dispersion and zero-dispersion wavelength over the wavelength range from 1515 nm to 1640 nm. NIST performs Special Test measurements of customer-supplied fibers over this range.

Plans for 2004:
Improve and verify absolute accuracy of 2 GHz modulation phase shift chromatic dispersion measurement system. Use a high-pressure gas absorption cell as an artifact standard to recalibrate the measurement system. Test chromatic dispersion and zero-dispersion wavelength measurements in an interlaboratory comparison.

Relative Group Delay (RGD)

Our RGD measurement work is directed toward assessing the achievable temporal resolution for our 200 MHz RF phase shift system, and establishing fundamental standards with theoretically predictable RGD profiles.

Plans for 2004:
Finalize uncertainty characterization of RF phase shift measurements to enable routine characterization of customer-supplied artifacts. Evaluate the effects of modulator chirp on RGD uncertainty and investigate this as a sensitive measurement of modulator chirp.

Polarization-Mode Dispersion (PMD)

We currently offer PMD measurements on customer supplied artifacts, and provide artifact standards for differential group delay (DGD), both mode-coupled and non-mode-coupled. We also have narrow-bandwidth measurement capability allowing measurements of DGD at 40 fs uncertainty in a 0.04 pm bandwidth for a single measurement, and 9 fs uncertainty for averaging.

Plans for 2004:
We will assess measurement uncertainties inherent in the measurement of Second-Order PMD (SOPMD), optimize techniques for low-noise SOPMD measurement, and compare performance of various techniques on a stabilized SOPMD artifact. We will also publish a summary of best practices in PMD measurement.

Component Spectral Transmission/Reflection

Fiber Bragg grating in temperature-controlled chamber for spectral reflection measurement. We have the capability to characterize spectral reflection profile in fiber Bragg gratings with an accuracy of 1 pm. This capability is supported by both a frequency-domain (tunable laser) technique and a low-coherence interferometric approach.

Plans for 2004:
Spectral characterization systems available for spectral reflectance profiling.

Optical Fiber Bragg Grating Characterization

We have the ability to measure longitudinal index profile of fiber Bragg gratings. We can do this with either a side-diffraction technique or a low-coherence interferometry (inverse scattering calculation). The latter technique promises to allow real-time monitoring of FBG index profile during the writing process. It also offers the ability to monitor temperature or strain in FBG sensors with a spatial resolution less than the length of the grating itself.

Plans for 2004:
Optimize our low-coherence interferometric system for sub-grating resolution of index profile and demonstrate remote measurement of FBG index profile during the grating writing process.