由於網際網路的快速發展，因此對於頻寬的需求日益增高，同時傳統的同軸電纜傳輸系統不僅高位元量傳輸已超過負荷，而且有顯著的雜訊出現在長距離傳輸時，因此逐漸被具有長距離傳輸與頻寬的光纖通訊所取代。目前光纖通訊已是成熟的通訊技術，分時多工（TDM）為其常用的通訊技術，此技術在傳輸位元量的限制與儀器設備上的需求較高，目前有新的分波多工（WDM）技術。
陣列波導光柵（AWG）為分波多工技術最重要建構模組(Building Blocks)的元件，並可運用於被動光網路（PON）系統中來改善整體傳輸的效能。陣列波導光柵由輸入與輸出波導、兩個星形耦合器（Star Coupler）與陣列波導（相鄰波導間有固定長度差（△L））所組成的元件。陣列波導光柵為良好的波長濾波器，但雙折射效應使陣列波導光柵有極化相關波長（PDW）效應的產生，造成中心波長的漂移。相位量測上使用中心波長1300 奈米的超螢光發光二極體（SLD）與可調變波長雷射（C-band）的光源，運用MZI架構產生干涉圖再接至分波多工耦合器（WDM coupler）。以可調變波長雷射的干涉圖的間距作為絕對光學尺的刻度，減少電動平移台移動誤差。陣列波導光柵主要是由波導陣列的相位差與功率分佈，經傅立葉轉換得到輸出頻譜，相位差與功率分佈的變動量使旁辦（sidelobe）變高，造成串音變差。在量測過程中，因製程誤差與波導幾何形狀不盡相同，造成波導陣列中每根波導有相異的有效折射率，形成相位差與功率分佈的變動量。此量測結果可經由傅立葉轉換成波長頻譜，我們可運用直接光學量測的方法來驗證。
光學低同調干涉（OLCI）是使用寬頻譜光源與延遲干涉獲得空間干涉圖形(Interferogram)，此光源與干涉圖形乃為傅立葉轉換，因此也稱為傅立葉光譜學，這是量測陣列波導光柵的相位差與功率分佈主要的理論依據。除了不同光源（ASE, SLD與DFB雷射）的空間干涉圖形的研發外，每個從陣列波導光柵的相位差與功率分佈的干涉圖均有詳細的理論驗證與實驗分析。而光學低同調干涉技術也適用於生物醫學檢測與雙折射效應的量測。

The Internet explosion has tremendously increased the bandwidth requirement. When a gigabit signal is run long distance over twisted pair copper, a lot of interference and noise problems will appear to hinder the transmission. Fiber optics networks can resolve this issue and significantly increase the transmission distance besides the bandwidth capacity expansion.
To an increase extent, optical fiber has been the medium of choice to handle this vast volume of traffic, and time division multiplexing (TDM) has been the most common way to divide the impressive capacity of a single optical fiber into useable communications channels. Even this technology, however, has been limited by the increasing complexity of modulation and multiplexing equipment as data rates soar. A new complementary approach has demonstrated its capabilities: wavelength division multiplexing (WDM).
An array waveguide grating (AWG) multiplexer is very attractive to be a useful technique and essential building block in optical WDM networks, the long/short haul telecommunications and passive optical networks, for its capability of increasing the aggregate transmission capacity of single-strand optical fiber. The AWG consists of input and output waveguides, two focusing slab regions, and a phase array of multiple channel waveguides with the constant path length between neighboring waveguides. Besides the filtering function on precise wavelength domains, AWG also owns the capability to characterize the modal birefringence, which can be observed as polarization dependent wavelength (PDW) shift on the central wavelengths. A phase measurement was utilizing a SLED source with 1.3-m wavelength and stabilized tunable laser source operating in the 1.5-m band, which were launched into the interferometer through the second input coupler port and separated at the output with WDM coupler. Copropagation of 1.3-m signal beams and the 1.55-m reference ensured a stable and accurate wavelength calibration that is insensitive to interferogram distortion caused by fiber temperature change or sampling-arm vibration. The crosstalk from the selective wavelength of AWG will be attributed to the phase and amplitude fluctuations in the entire electric field profile at the output side array-slab interference since the focused beam profile at the output plane is the spatial Fourier transform of the electric field in the array waveguides. Amplitude and phase fluctuations in the entire electric field profile cause imperfect focused beam profile, in which sidelobe level becomes higher. Then the crosstalk becomes much worse. The amplitude fluctuation is caused by non-uniformity in the array waveguides. The phase fluctuation is actually an optical path length fluctuation in each array waveguide, caused by the non-uniformity in refractive indices and core geometries in the array waveguide region. The phase error from the entire grating waveguides was utilized to verify AWG spectrum crosstalk using an isomorphic Fourier transform.
Optical low coherence interferometry (OLCI) uses a continuous-wave broadband source and a variable-delay interferometer to obtain a spatially-localized interference fringe pattern or interferogram. When the interferogram is Fourier transformed, the spectral density of the broadband source is obtained. In this thesis, the device under test of AWG was measured the frequency response (magnitude and phase) by placing it on one arm of an interferometer. This method is also called Fourier spectroscopy. The fringes number in interferogram was demonstrated as the grating waveguide channels of AWG. To study the interferometry resolution, the different sources of amplified spontaneous emission (ASE) and super-luminescent light emitted diode (SLED) were theoretically and experimentally studied. The phase sensitivity from OLCI was also demonstrated to be applied to the biosensors and birefringence characterization on optical waveguides.

[1] K.Okamoto, ”Fundamentals of Optical Waveguide”, San Diego, Academic Press, 2000
[2] D. K. Cheng, “Field and Wave Electromagnetics”, 2nd ed., Addison-Wesley, 1989
[3] Joseph C. Palais著，董德國，陳萬清譯，“光纖通訊”，東華書局，2000年
[4] G. T. Reed and A. P. Knights, “Silicon Photonics An Introduction,” John Wiley & Sons, Ltd.
[5] S. O. Kasap, "Optoelectronics and Photonics" Prentice Hall, 2001
[6] A. Yariv and P. Yeh, “Photonics: Optical Electronics in Modern Communications,” New York: Oxford (2007)
[7] A. Kaneko, T. Goh, H. Yamada, T. Tanaka and I. Ogawa, “Design and applications of silica-based planar lightwave circuits” IEEE Journal on Selected Topics in Quantum Electronics, 5 (5), pp. 1227-1236,1999
[8] M.C. Parker, S.D. Walker and R.J. Mears, “An isomorphic Fourier transform analysis of AWGs and FBGs” IEEE Photonics Technology Letters, 13 (9), pp. 972-974,2001
[9] M.C. Parker, S.D. Walker, A. Yiptong and R.J. Mears, “Applications of active arrayed-waveguide gratings in dynamic WDM networking and routing” Journal of Lightwave Technology, 18 (12), pp. 1749-1756,2000
[10] M.C. Parker and S.D. Walker, “An Isomorphic Fourier Transform Approach to Light Propagation in AWGs, FBGs, and Photonic Crystals” Proceedings of the Joint Conference on Information Sciences, 6, pp. 1322-1326,2002
[11] M.C. Parker, S.D. Walker, A. Yiptong and R.J. Mears, “Applications of active arrayed-waveguide gratings in dynamic WDM networking and routing” Journal of Lightwave Technology, 18 (12), pp. 1749-1756,2000
[12] K. Iizuka, Elements of Photonics, New York, John Wiley, 2002
[13] K. Takada , Y. Inoue , H. Yamada and M. Horiguchi “Measurement of phase error distributions in silica-based arrayed-waveguide grating multiplexers by using Fourier transform spectroscopy” Electronics Letters, 30 (20), pp. 1671-1672,1994
[14] K. Takada , M. Amada and S. Satoh “Wavelength-adjustment-free optical low coherence interferometry for high-resolution and highly accurate optical network analysis of arrayed-waveguide gratings Optics Communications, 252 (1-3), pp. 73-77, 2005
[15] H. Yamada , H. Sanjoh, M. Kohtoku , K. Takada and K. Okamoto “Measurement of phase and amplitude error distributions in arrayed-waveguide grating multi/demultiplexers based on dispersive waveguide” Journal of Lightwave Technology, 18 (9), pp. 1309-1320,2000
[16] K. Takada, H. Yamada and Y. Inoue “Optical low coherence method for characterizing silica-based arrayed-waveguide grating multiplexers ”Journal of Lightwave Technology, 14 (7), pp. 1677-1689,1996
[17] W. Chen , Y.-J. Chen, M. Yan , B. McGinnis and Z. Wu “Improved techniques for the measurement of phase error in waveguide based optical devices” Journal of Lightwave Technology, 21 (1), pp. 198-205,2003
[18] A. Densmore, D.-X. Xu, P. Waldron, S. Janz, A. Delâge, G. Lopinski, T. Mischki, P. Cheben, E. Post, J. Lapointe and J.H. Schmid,“Label-free biosensing using silicon planar waveguide technology”Proceedings of SPIE - The International Society for Optical Engineering, 6796, art. no. 67962X,2008
[19] A. Densmore, D.-X. Xu, P. Waldron, S. Janz, A. Delage, P. Cheben and J. Lapointe“Thin silicon waveguides for biological and chemical sensing”Proceedings of SPIE - The International Society for Optical Engineering, 6477, art. no. 647718,2007
[20] 林慧琪、許芳文“利用光學同調斷層掃描術量測氯化鈉水溶液濃度與折射率之關係,” OPT’07, Taiwan, (2007)