The substrates have a coefficient of thermal expansion that is greater than that of the dielectric layers, and the thicknesses of the substrates are selected to provide compensation for temperature dependant variations in {HEAD ~ the center wavelength} of {TAIL ~ the filter} 
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The substrates have a coefficient of thermal expansion that is greater than that of the dielectric layers , and the thicknesses of the substrates are selected to provide compensation for temperature dependant variations in { HEAD ~ the center wavelength } of { TAIL ~ the filter }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL