One of the promises of coherent systems is that they can handle very high levels of polarization mode dispersion (PMD), but is that really the case? Each wavelength has a different instantaneous PMD (referred to as differential group delay or DGD) that is uncorrelated with the next wavelength and changes over time. The average of all these DGDs at individual wavelengths is what we call PMD. Coherent systems feature digital signal processing (DSP) technology that tracks and compensates in real-time for the variations in DGD on a per-wavelength basis.

Combining PMD and CD into one test solution that enables technicians to characterize multiple links from a single location, the FTB-5700 is built specifically for today’s high-speed network reality. Its highly intelligent interface and functionalities ensure that test parameters are automatically optimized, whatever the link./

EXFO’s FTB-5600 is the very first quantitative distributed PMD analyzer on the market. The technological breakthrough on which it is based provides operators with a cost-effective, time-efficient alternative to costly network upgrades. By breaking down the PMD measurement results, distributed PMD analysis pinpoints high-PMD sections and accurately qualifies them. The example to the right details a real-world network upgrade scenario, and shows the type of results generated by the FTB-5600 in such situations.

One of the promises of coherent systems is that they can handle very high levels of polarization mode dispersion (PMD), but is that really the case? Each wavelength has a different instantaneous PMD (referred to as differential group delay or DGD) that is uncorrelated with the next wavelength and changes over time. The average of all these DGDs at individual wavelengths is what we call PMD. Coherent systems feature digital signal processing (DSP) technology that tracks and compensates in real-time for the variations in DGD on a per-wavelength basis. However, DSPs can compensate for a limited range of DGD, and they have a limited reaction time to changes in DGD. Since DGD changes over time, very high DGD values can occur, and may therefore exceed the compensation range of the DSP. Similarly, DGD sometimes changes very rapidly, and even faster than the DSP is able to track, leading to loss of PMD compensation. It can also be sudden changes in state of polarization that lead to a complete loss of signal. When that happens, the DSP tries to resynchronize and rediscover the level of PMD that needs to be compensated for. While it usually does this very quickly, many bits will have gone by uncompensated for, potentially generating a lot of errors in the process

The FTB-2200 Broadband Source is a high-power, polarization-scrambled broadband LED source covering the C + L bands. It is ideal for conducting high-accuracy PMD measurements and was specifically designed to work with EXFO’s FTB-5500B PMD Analyzer to provide the most accurate and fastest PMD measurements in the field.

The FLS-5834A’s high modulation makes it a perfect complement to the FTB-5800 Chromatic Dispersion Analyzer, whose technology is based on the phase-shift method. This first-class duo lets you run chromatic dispersion (CD) measurements through amplifiers such as EDFAs, providing the highest accuracy in field CD testing.

The FLS-110 offers CW and 2 kHz modulation for fiber identification, complete status indicators, low-battery indicator and an auto-off function. The unit is housed in a sturdy, waterproof case surrounded by a shock-absorbing holster that protects the instrument in tough field conditions. Choose between the O band or the C band LED models. Both units feature high and low power levels to maximize battery life.

Test access module (TAM) is the common and standard name given to a fiber-optic coupling element, which is used in remote testing and monitoring applications to combine the OTDR signal with traffic. The device used to perform this function is typically a coupler. Some are broadband-type, others are WDM-type or wavelength-division multiplexers, which are spectrally sensitive combiners.

Optical test access units (OTAUs) are test access units that are used to programmatically connect a fiber under test to test equipment through an optical switching subsystem. This product can create a temporary and low-insertion loss optical path between the test equipment and the fiber when characterizing, troubleshooting or testing any degradation (monitored). OTAUs are designed to be connected to an OTDR, specifically EXFO’s Fiber Guardian, thus allowing a single instrument to test up to 720 fibers in a very dense capacity.