| Multichannel optical communication systems, such as wavelength-division multiplexing (WDM) and dense wavelength-division multiplexing (DWDM) was made possible by the realization of several optical components. In dense-wavelength division demultiplexing systems (DWDM), hundreds of channels, closely spaced in wavelength, are sent simultaneously over the same optical fiber. Spectral filters are required for demultiplexing all these wavelengths at the receiving end. The thin film interference optical filter operates with the same principle as the Fabry-Perot interferometer. When the incident angle is increasing, its passband and the transmission peak will shift to the shorter wavelength(blue shifted). An optical filter is one of the most critical component. In order to increase the channel information capacity of the optical fiber, the bandpass filter must have a wide bandwidth, covering the wavelength deviation of the signal light. For optical telecommunication applications, the 1300 nm and 1550 nm wavelength windows are mainly considered. Recently, there has been a growing interest in the application of the interference optical filter in DWDM broadband optical communication systems.With the development of modern telecommunication and networks, more and more attentions have been paid to dense-wavelength-division multiplexing (DWDM) systems. And thin-film interference multiplexer has been very attractive in optical DWDM networks since it is capable of increasing the aggregate transmission capacity of single strand optical fiber. So, it becomes one of the key technologies in studying DWDM systems to design the coating configuration of thin-film interference optical filter and develop its performance.Three proposed approaches are used to obtain narrowband multichannel filters. The first approach is using multiple hetero structures inserted with defects mode. The enlargement of the forbidden band and the realization of multiple channeled filtering can be reached simultaneously by using this method. The second approach is using guided -m ode resonance Brewster filters with multiple channels. For this method, narrowband filters with multiple channels can not only be obtained by using single layer structure, but also be obtained by using double layer structure with equal refractive index. The third approach is integrated optical filter arrays using the combinatorial etching technique. Single and double chamber narrowband filter arrays can be both obtained by using this method. Narrowband multichannel filters obtained by using these three methods are potentially useful in many optical applications. In this paper , the first method is used, that is, we get access to multichannel thin-film optical filter with the number of defects heterojunction structure, with different thickness for the one-dimensional photonic crystals, if they are linked up, multi-heterojunction structure is formed. If the defect was introduced into the multi-heterojunction structure, then in the photonic band gap, the formation of defect levels are formed Correspondingly, some specific frequency of light can appear in these defect levels, resulting in the emergence of multichannel effect .The main work of this thesis is focused on two kinds of ultra wide band multichannel thin-film optical filter optimization of design and thin film design software, including an analysis of the principle of thin film optical filter and structural design, designing a thin film design software, and compared with thin-film design software TFCalc performance it is simple, easy to learn, easy to understand and so on. Paper are as follows:Firstly, we summarize the development of WDM and instruments, make an introduction and comparison with the commercial MUX/DEMUX , illustrate the MUX/DEMUX based on thin film optical filter and advance the necessity of developing novel MUX/DEMUX based on thin film optical filter. We also illustrate optical thin-film in the application of DWDM system, the review and development condition of the optical thin-film technology and the applied condition of optical thin-film technology in DWDM.Secondly, we introduce the calculation of the performance of optical thin-film and the principle of error analysis. The relationship between the spectrum(including stopband and passband width, steepness and ripples) and the film structure of multi-cavity filter is analysed firstly. Unlike the explict relationships, such as the dependence of the bandwith on reflectors and interference lever, or the steepness on the cavity number, the character of ripple in the passband is much more complex. With the concept of absentee, some ways are gained to suppress the ripple. The structure design and error analysis of ultra broadband multiple-channel filter is reasonedly studied in this thesis, together with a great deal of coating experiments. Based on Fabry-Perot structure, a multiple-channel filter is obtained in theory by changing the structure of spacer layers. In order to control the position and width of adjacent routeways, different cavity structures were studied. It is concluded that the width of adjacent routeways can be changed by changing the optical thickness of spacer layers. The angular performance of the filter is investigated in terms of spectral shift of transmittance towards shorter wavelengths with the increase of the angle of incidence.We design two kinds of ultra broadband multichannel narrow-band optical thin-film filter and ultra broad band multichannel wide-band optical thin-film filter. The layer sensitivity of ultra broadband multichannel narrow-band optical thin-film filters, is thoroughly analysed. The layer sensitivity of ultra broadband multichannel wide-band optical thin-film filters, varying from three-cavity to five-cavity, is also thoroughly analysed. The sensitivity geny is strongly determined by the position of layer in the cavity. Cavity layers are the most sensitive ones in a cavity and coupling layers, the least. The further the layer is away from the cavity layers, the little the sensitivity of the layer. If no irregular layers are added on the filter, layers in outer cavities are sensitive than their corresponding layers in inner cavities. These differences disappeared after adding irregular layers. Tolerances of the filter are calculate based on different monitor methods. A special monitor method, under which the filter has the maximal tolerance, is gotten. The theoretic supportance for this method is studied. The tolerances of different film structure are calculated and compared.At last, based on these ways, a programme is built to search filters that have low insert loss, sharp slop and high quality factor. The result of 100GHz-interval filters, which meet the target of performance searched by the programme with, is given in the thesis. |
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