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Study of Optical Implementation and Integrated Technology of Free-Space Optical Interconnection Network

Author: ZhangHuaLiang
Tutor: TanJiChun
School: National University of Defense Science and Technology
Course: Physics
Keywords: Optical interconnection Perfect Shuffle transform Optical switch Optical waveguide Grating coupler SOI substrates
CLC: O438
Type: Master's thesis
Year: 2011
Downloads: 36
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Abstract

With the development of modern science and technology and the expansion of social requirement, the limitations of electrical interconnection became increasingly clear. While optical interconnection networks may play an important role in the future telecommunication systems and multiprocessor computer systems, since the signal delay and skew can be greatly reduced. Compared to the ripe electrical interconnection, the main features of the optical interconnection are as follows:1. There is no delay of the resistance-capacitance (RC) .The bandwidth of the optical frequency is nearly unlimited. Thus, the transmission rate of the optical signal is hundreds of times as high as that of the electrical signal. The optical interconnection conforms to the requirements of the transmission signal having super high speed and large capability.2. The light wave is not sensitive to interference and the optical signal can be paralleled and overlapped stereoscopically, so the density of the optical interconnection is greatly increased.3. Since the frequency of the electromagnetic wave is far away from the light wave frequency, the optical interconnection does not suffer from the electromagnetic wave.4. The programmable and dynamic interconnection is easy realized by the optical method, but it cannot be implemented with electrical circuits. This paper is supported by the National Natural Science Foundation of China and the Foundation of National University of Defense Technology. The optical implementation of free space optical interconnection and its integrated technologies are studied in this thesis. Free space optical interconnection is implemented by using traditional 4-f optical system and sinusoidal grating, and the on-chip optical interconnection network based on single silicon substrate is realized in terms of the waveguide grating coupler and silicon waveguide. In addition, the optical switch of free space optical interconnection is also studied in detailed.A number of achievements were obtained through the theoretical and experimental study of the free space optical interconnection and its integral technologies, which include:1. The implementation of the free space optical interconnection using 4-f optical system and sinusoidal grating is testified in theory, and the Left Perfect Shuffle and Right Perfect Shuffle transformation are implemented by 4-f optical system and sinusoidal grating in laboratory.2. 1×2、2×2 and 2×4 optical switches are proposed with conventional polarization controlling technology by using phase spatial-light modulator(PSLM), polarized beam splitter(PBS) and reflective mirror, etc. The inter-channel crosstalk and the insertion loss of 1×2、2×2 optical switches are tested in laboratory. According to the experiment results, the minimum of the insertion losses are 0.54dB and 0.70dB, respectively. The inter-channel crosstalks are -23.9dB and -24.0dB, respectively.3. A compact multilevel grating coupler and binary blazed grating coupler based on SOI material structure are also proposed to realize coupling between fiber and waveguide, which can be integrated with other SOI components. The result shows that the multilevel grating coupler has the 3dB bandwidth of 160nm from 1390nm to 1550nm, with the coupling efficiency of approximately 50% at the wavelength of 1550nm and 67.5% at 1460nm. The coupling efficiencies from a fiber to waveguide of the binary blazed grating are 59.2% at the wavelength of 1550nm and 76.9% at 1563nm. A 3 dB bandwidth of 33nm is also obtained. The numerical simulation also shows that the tolerances of 19nm in etched depth and 6.5o in incident angle are achievable.4. The implementation of 4×4 and 8×8 Left Perfect Shuffle using silicon waveguide is simulated by FDTD software. The results show that the silicon waveguide can implement optical interconnect with high transmission efficiency, low insertion loss and crosstalk. The transmission efficiency of the straight waveguide can be up to 99.79%. The transformation efficiency of cross waveguide is about 80%. While the crosstalk is very low, up to 1.1%.5. Using of SOI substrates in the laboratory, we produced a waveguide grating coupler and the waveguide structure to achieve Left Perfect Shuffle transform, to our knowledge, which initially implemented the on-chip optical perfect shuffle based on silicon substrate. And the system has relatively low crosstalk, at -11.9 and -14.8dB. The results show that the optical interconnection based on silicon substrate has lots of advantages, such as small size, ease of integration, etc.

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