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February, 2002 Two New Calibration Standards for Optical Fiber Communications |
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The EEEL Optoelectronics Division is releasing two artifact calibration standards relating to polarization dependent measurements in optical fiber telecommunications applications.
NIST will provide traceable measurements for polarization dependent loss (PDL) in optical fiber and fiber components, using an artifact standard made available to customers through a Measurement Assurance Program (MAP). Rex Craig developed the artifact and will conduct the MAP. When PDL is combined with polarization-mode dispersion in a communication channel, the bit error rate is degraded. Therefore accurate measurements are necessary to enable high data rate communication systems. The MAP artifact consists of a short section of polarizing fiber spliced to a single mode input fiber and a step-index multimode output, and its PDL is certified over the 1535-1560 nm wavelength range. The artifact is implemented as a MAP (rather than an SRM) to mitigate the degradation to uncertainty that is caused by exposure of the artifact to unpredictable temperatures. The MAP implementation includes a recording thermometer to indicate the temperature exposure of the device during the customer measurement process.
An additional SRM for polarization mode dispersion (PMD) will expand NIST traceability in this area. In an optical fiber communication system, propagation velocity depends on the polarization state of the light. The resulting polarization-mode dispersion (PMD) can broaden optical pulses and limit bit rate. The new SRM, developed by Paul Williams, is SRM 2538, Polarization-Mode Dispersion, Non-Mode-Coupled. It is the second SRM for PMD. The first, SRM 2518, emulates the differential group delay in a long length of optical fiber. The new artifact, SRM 2538, is a fiber-pigtailed quartz plate, designed to emulate the PMD typically found in telecommunications components. This new SRM is certified for mean Differential Group Delay (DGD) over a wavelength range of approximately 1250-1650 nm. SRM 2538 is certified for measurement by all PMD techniques (subject to instructions in the documentation). Due to technical constraints, SRM 2518 is certified for only a particular class of PMD measurement techniques.
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