Characteristics And Analysis Of Spatial Frequency Domain Of Arrayed Waveguide Grating

With the rapid development of photon technology and the apparent advantages of the integrated optic system over the conventional bulk optics system; the concept of "integrated optics" has penetrated into the various domains of optical information technology. It is of great significance to realize the optical integration of coherence system because the system is fundamental in the optical information process and widely utilized in the optical information process domain.The arrayed-waveguide grating (AWG) bases on the planar linear circuit technology of Si substrate has two elementary functions: one is multi/demultiplexer, the other is static wavelength router. AWG has been extensively applied in the optical fiber communication domain and become one of the key devices in the Dense Wavelengths Division Multiplexer (DWDM). From the point of spatial frequency domain the paper applies the spatial frequency transformation to analyze the AWG transmission characteristics and probes into the function of Fourier transform, the characteristics of coherent system and its application in optical information process domain.The paper first presents the configuration, the principle, the applications, new development in the WDM system and the solutions to relevant problems of AWG Then the paper introduces the theory basis of spatial frequency analysis of AWG: fundamental Fourier optics.Based on the above mentioned, from the point of spatial-frequency domain, the paper analyzes the change of light field intensity in different phases when optical signal of fundamental mode transmits hi AWG The general expression of AWG's transimission characteristics is obtained. And then we study property of coherencesystem of AWG The whole AWG can be regarded as an optical transmission system, whose transmission property is chiefly determined by the transmission property of the slab waveguide and arrayed-waveguide. The diffraction process of light beam inputed in slab waveguide is a process of "decomposing frequency and composing spectrum". The angle spectrum of inputting optical signals is received by the input surface of arrayed waveguides.Whereas the diffraction process of light beam outputed in slab waveguide is a process of "composing frequency and generating image". The reason that Fraunhofer diffractive pattern can be gained on outputting waveguide surface is that output ends of arrayed waveguide distribute on the arch structure which leads bent phase factor to offset the quadratic phase factor in Fresnel diffraction. The essence of two kinds of diffractive process is spatial Fourier transformation. The process that light wave gets through arrayed waveguides can be regarded as a process of extracting spatial sample and filtering spatial frequency. Spacial sample is accomplished by period interval arrangement of AWG and spatial frequency filtering is accomplished by the fundamental mode and phase delay of each arrayed waveguide which is just a spatial frequency filter. AWG possesses an essential function of coherence system-"composing frequency and generating image". Therefore as far as spatial frequency field is concerned, AWG is an optical integration of coherent system: two slab waveguides similar to two Fourier lenses of one dimension and twice Fourier transform of optical signals are realized. Here the arrayed waveguide region is frequency spectrum region.On the other side, we use the method of optical formation process to introduce two fundamental filtering function in frequency domain of coherence system of AWG Two optical processors are designed, that is optical signal add/minus and phase filter. By setting a amplitude filter(module) with certain transmission function in arrayed waveguides, we design optic signal add/minus. By changing the length ofcenter arrayed waveguides, we design phase foil filter of AWGUltimately, the present stage work are summarized and some future work are discussed.