White Paper CWDM components for 40 G and 100 G Transceivers D-5006 Results As we approach the 10-degree angle, the insertion loss is at a minimum. The loss increases dramatically as we deviate from the minimum loss point. This variation off the 10-degree correlates with loss found in the y-axis, the ability to confine the angular variation in the x-axis will yield better insertion loss performance. The data assumes that only one filter is misaligned. If more filters are misaligned the loss penalty gets even higher. Angular tolerance as a function of filter pass band performance The filter pass band performance can also change as a function of angular variations associated with the tolerance of the filter placement and temperature effects. The pass band shifts as a function of Angle of Incidence (AOI) can be expressed with the following graph. Center Wavelength Shift [nm] 0,0000 0,000 -1,0000 -2,0000 -3,0000 -4,0000 -5,0000 -6,0000 -7,0000 -8,0000 -9,0000 2,000 4,000 6,000 8,000 10,000 12,000 14,000 AOI [deg] On the x-axis is the angular variation expressed in degrees. On the Y-axis is the shift in pass band. If we look at the nominal value of 10 degrees, the value of the center wavelength shift is approximately -5.5 nm. The chart below shows the region around 10 degrees where the slope of the angular variation vs. CWL shift is approximately linear. Center Wavelength Shift [nm] -4,0000 9,000 -4,5000 9,200 9,400 9,600 9,800 10,000 10,200 10,400 10,600 10,800 11,000 -5,0000 -5,5000 -6,0000 -6,5000 -7,0000 AOI [deg] Document: D-5006 Page 2/4
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