DWDM(Dense Wavelength Division Multiplexer)濾光片為光纖通訊系統中重要的光學元件，由於其膜厚較厚所以會產生較大的應力，當濾光片受熱，會受熱應力影響而改變濾光片的光學厚度，結果濾光片中心波長將隨溫度變化而產生飄移。Takahashi首先以應力模型為溫飄提出理論分析，基板的熱膨脹係數，薄膜的折射率、楊氏模數、帕松比、熱膨脹係數及折射率溫度係數等，均為影響溫飄的重要參數。而符合國際規範的DWDM 100GHz濾光片溫飄必須小於1pm/℃，也因此使得膜層數及膜厚增加。而在此情況下應力模型需要修正，同時也增加考慮應力對於折射率影響的應力光學常數。因此本論文即提出厚度修正後的應力模型分析應力對於DWDM濾光片中心波長飄移量的影響。也利用修正後的應力模型經實驗求得DWDM濾光片薄膜的線膨脹係數為0.87 ppm/℃。再由擬合實際溫飄值求得薄膜雙軸模數為41 GPa、帕松比為0.22、折射率溫度係數為1.4×10-5/℃、應力光學常數為-1.9×10-12 /Pa。以及SiO2的折射率溫度係數為2.0×10-5 /℃、應力光學常數為-1.9×10-12 /Pa；Nb2O5的折射率溫度係數為7.6×10-4 /℃、應力光學常數為-9.73×10-11 /Pa，而以上薄膜的相關資訊皆可提供未來設計DWDM濾光片的相關依據。Dense-wavelength-division-multiplexing (DWDM) filter is a kind of very important component for optical fiber communication. Since any tiny wavelength shift will make the filter ineffective. The temperature shift of central wavelength (TSCW) of DWDM filters has to be limited less than 1pm/oC based on the Bellcore GR-2883 standard. The TSCW of filters are depended on the mechanical properties of the stress. Takashashi was the first one to construct the theoretical model of TSCW using the Elastic Strain model in 1995. This model based on the Stoney’s equation showed that the most important parameters are CTE of the substrate and the film, besides the refractive index, Young’s modulus, Poisson ratio, the normalized temperature coefficient of refractive index (NTCRI) of the film are important too. However, when the thickness ratio of the substrate and the film is larger than 1%, the Stoney’s equation should be modified. Using the modified Stoney’s equation the CTE of the DWDM filter about 0.87 ppm/oC have been achieved. Then measured the TSCWs of different sizes and substrates of DWDM filters, we can achieve other parameters, the biaxial modulus, 41 GPa; the Poisson ratio, 0.22; the temperature coefficient of refractive index, 1.4×10-5/oC; and the stress-optic coefficient, -1.9×10-12 /Pa. With all the parameters we can predict the TSCWs of the different DWDM filters.
