HIGH RESOLUTION WAVELENGTH CALIBRATION SRM FOR WAVELENGTH DIVISION MULTIPLEXING.

Wavelength calibration references are needed in the 1500 nm region to support wavelength division multiplexed (WDM) optical fiber communication systems. In a WDM system, many wavelength channels are sent down the same fiber, thereby increasing the bandwidth of the system by the number of channels. If one channel's wavelength were to shift, crosstalk could occur between it and a neighboring channel. NIST scientists have developed a new wavelength reference that is now available as Standard Reference Material (SRM) 2517a. The SRM is an upgrade of SRM 2517; it enables much higher accuracy wavelength calibration of test and measurement equipment.

SRM 2517a, High Resolution Wavelength Calibration Reference for 1510 nm to 1540 nm, can be used to calibrate the wavelength scale and linearity of wavelength measuring equipment. The SRM is a single-mode optical-fiber-coupled absorption cell containing acetylene gas at a pressure of 6.7 kPa (50 Torr). The main difference between SRM 2517a and its predecessor, SRM 2517, is the use of lower pressure in the acetylene cell to produce narrower absorption lines. The lines are about a factor of four narrower than those of SRM 2517. The NIST researchers made accurate measurements of the pressure-shift of the acetylene lines in order to certify the center wavelengths of 56 lines. Fifteen of the lines are certified with an uncertainty of 0.1 pm (about 12 MHz), two lines are certified with an uncertainty of 0.6 pm, and the remainder of the lines are certified with an uncertainty of 0.3 pm. This can be contrasted with the predecessor SRM 2517, whose lines were certified with 0.6 pm uncertainty. Thus SRM 2517a extends the use of this SRM to higher resolution and higher accuracy applications.