June, 2005

EEEL Develops High Accuracy Wavelength Calibration SRM

William Swann and Sarah Gilbert of the EEEL Optoelectronics Division have developed a new wavelength reference for the 1530 to 1565 nm region that is now available as Standard Reference Material (SRM) 2519a. The SRM is an upgrade of SRM 2519 and is more than an order of magnitude more accurate than its predecessor. Thus, SRM 2519a enables much higher-accuracy wavelength calibration of test and measurement equipment.

Wavelength calibration references are needed in the 1500 nm region to support optical fiber communication and sensor systems. Wavelength division multiplexed (WDM) optical fiber communication systems increase bandwidth by using many wavelength channels. Current WDM systems typically employ 50 or 100 GHz channel spacing (0.4 or 0.8 nm, respectively) in the 1530 to 1565 nm WDM C-band. Wavelength references are needed to calibrate instruments that are used to characterize components and monitor the wavelengths of the channels. In addition, optical fiber sensors based on the wavelength shift of fiber Bragg grating reflection peaks require wavelength calibration. For precision strain and pressure measurement, some of these sensor systems need wavelength calibration references with better than 1 pm uncertainty. Fundamental atomic or molecular absorption lines provide wavelength references that are very stable under changing environmental conditions. SRM 2519a is a single-mode optical-fiber-coupled absorption cell containing hydrogen cyanide H¹³C¹⁴N gas at a pressure of 3.3 kPa (25 Torr); the molecule has more than 50 strong absorption lines in the 1530 to 1565 nm region. This new SRM has narrower absorption lines than its predecessor, and the NIST researchers made accurate measurements of the centers, pressure shift, and pressure broadening of the absorption lines. The center wavelengths of 54 lines of the hydrogen cyanide absorption band are certified with uncertainties ranging from 0.04 pm to 0.24 pm, corresponding to a frequency uncertainty ranging from 5 MHz to 30 MHz. This new SRM is the highest accuracy wavelength calibration SRM in the absorption cell series, which includes SRM 2517a (acetylene, 1510 to 1540 nm) and SRMs 2514 and 2515 (carbon monoxide, 1560 to 1630 nm).

Contact:

Sarah Gilbert, (303) 497-3120