The Theoretical Research Of The Fabrication Of Arrayed Waveguide Grating With UV-Writing Technology

With the rapid growth of the global telecommunications business and the urgent needs of the high-speed large-capacity broadband integrated services network, a modern communications network technology is promoted in the development of high-speed. The WDM technology can achieve great capacity and versatility, for the future all-optical networks, WDM will play a leading role. The Arrayed Waveguide Grating WDM technology is the key to one of the devices. It has a lot of advantages such as a low insertion loss, narrow wavelength spacing, small size, easy optical integrating, much more signal channels, low crosstalk, and flat output. And AWG is regarded as the most promising of a new type of wavelength division multiplexing devices. Therefore, lately it becomes one of the researchful hotspots all over the world.In this paper, the fabrication of arrayed waveguide grating make uses of UV-writing technology. UV-writing technology It has a lot of advantages such as simple process, good reproducibility, low cost, short production cycle; The fabrication of arrayed waveguide grating devices with UV-writing technology will also have low insertion loss, independent of polarization, low crosstalk and accurate center wavelength so on.This technology not only can be simplified the fabrication process of AWG and avoid expensive etching equipment, but also can be greatly improved the parameters of the device through the on-line measurement, more importantly, because of melting process, which allows us to design and manufacture more New integrated devices, such as the integration of Interleaver and grating, coupler and grating.The AWG multiplexer/ demultiplexing consists of input/output rectangular waveguides (i.e. I/O channels), two focusing slab waveguides, and an AWG which contains numbers of arrayed rectangular waveguides. The AWG joins the two slabs and provides a constant length difference between adjacent arrayed waveguides. In this paper, the operation principle and fundamental characteristics are presented according to the waveguide model equation and basic grating principle, such as angle dispersive, free spectral range (FSR), inching function, wavelength distributing and so on.AWG possesses some advantages, such as easy optical integrating, narrow wavelength spacing, much more signal channels, low crosstalk and excellent particular features, such as easy fabrication, low propagation loss, small birefringence, and easy control of the refractive index. Relatively the theory about AWG is mature. The current direction of development of AWG is on the basis of the improvement of its performance to promote its functions. AWG can offer some basic functions including multiplexing/ demultiplexing, optical add/drop multiplexing (OADM) and optical interconnection. So the AWG multiplexer has attracted much more attention. Recently, considerable attention and great efforts have been focused on the development of polymer AWGs.In this paper, based on the electric-magnetic theory, we introduced the E_mn^y mode and E_mn^x mode, and the width and the effective refractive index of the waveguide are given. According to the results we have got, we optimized a polymer AWG multiplexer. First some important parameters are optimized for the structural design of a polymer AWG multiplexer around the central wavelength of 1.55μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, mode effective refractive indices and group refractive index, diffraction order, pitch of adjacent waveguides, length difference of adjacent arrayed waveguides, focal length of slab waveguides, FSR, the number of input/output channels, and that of arrayed waveguides. Then the bent angles, radii and lengths of all the input/output channels and arrayed waveguides are determined.The transmission characteristics play important roles in the application of AWG to telecommunication. The transmission characteristics are analyzed for a polymer AWG multiplexer around the central wavelength of 1.55μm with the wavelength spacing of 1.6 nm. We introduce the expressions of the normalized field of AWG according to the AWG diffraction theory. The power profile in the input slab waveguide and output slab waveguide are analyzed, transmission spectrum, diffraction efficiency, polarization and crosstalk are investigated and discussed for different values of parameters, such as the core width, pitch of adjacent waveguides, the number of arrayed waveguides, propagating wavelength and diffraction order. Larger core width and larger number of the arrayed waveguides lead to weaker background of the output power profiles and transmission spectra of the device. Smaller pitch of adjacent waveguides, larger core width and larger diffraction order can result in higher diffraction efficiency. By using a taper to widen the input ends of the arrayed waveguides, the diffraction efficiency can be increased efficiently. There exists a minimum of the crosstalk with the variation of the pitch of adjacent waveguides. Therefore, we should select its value nearby this minimum to reduce the crosstalk of the device. Finally, optimized values of parameters are given.In the study of AWG, the key problem is how to reduce the insertion loss. In this paper, the loss characteristics are analyzed for this polymer AWG multiplexer around the central wavelength of 1,55μm with the wavelength spacing of 1.6 nm. The total loss of the device includes the diffraction loss in the input and output slab waveguides, bent loss caused by the AWG and I/O channels, and leakage loss resulted from the high refractive index substrate. The effects of some structural parameters on the loss characteristics are investigated and discussed. Smaller pitch of adjacent waveguides, larger core width and larger diffraction order can result in lower diffraction loss. We should notice that the core width and diffraction order number should be selected properly, that is, they should not be taken too large. If the core width is too large, higher order modes will propagate in the device. If the diffraction order number is too large, the number of the I/O channels will be too small. Larger bent radius of the waveguide leads to lower bent loss in the AWG and I/O channels efficiently. However, the bent radius of the waveguide should not be taken too large, if not, the size of the device would be too large. Larger thickness of the confined layer between the core and the substrate results in lower leakage loss caused by the high refractive index substrate. Absorbing loss caused by the material of waveguide can be reduced from enhancing the performance of material.During the entire process of analysis and research, a typical case of The AWG multiplexer/ demultiplexing is with center wavelength of 1.550918μm, the channel spacing of 1.6 nm and 7 I/O channels. In the process of theoretical analysis and simulation design, we use matlab language to design a program, C language is an assistant tool. All of my work have been very good test results and conclusions.