High speed photodiode and 90° optical hybrid for 2 µm optical communication systems

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Ye, Nan
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University College Cork
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In order to maximize the capacity using these C-band wavelengths, more and more efforts have to be exerted by the equipment providers to increase capacity and suppress cross talk between adjacent channels. To overcome this capacity saturation around 1.55 µm, the next generation optical networks require technological developments in new wavelength regions. This will not only extend the current effective transmission band but also address limitations such as loss and non-linearity of silica-core fibers. The waveband at 2 µm can be recognized as a potential candidate due to the low loss window in Hollow Core Photonic Band Gap Fibers (HCPBGF) and the gain bandwidth from Thulium Doped Fiber Amplifier (TDFA). Furthermore this waveband can take advantage of the previous research and development ideas based on 1.55 µm while extending the technologies related to materials and processing for the passive and active components. To satisfy the system-level applications at this new wave band, opto-electronics devices at 2 µm should be developed. In this thesis, we present the building blocks regarding material optimization, device design, process development and performance characterizations of high speed photodiodes and associated 90° optical hybrids at 2 µm. All types of the photodiode devices have been packaged with the support from the package group for high speed test to prove the ability to work in the real optical communication system. For the optical 90° hybrids, design of large spot size diluted waveguide, dimension optimization of 4×4 Multiple Mode Interference (MMI) coupler, and monolithic integration test structure involving hybrid and Mach-Zehnder Interferometer (MZI) are achieved. The devices have displayed the potential to be applied in real 2 µm optical communication systems while the photodiode is also useful in gas sensing area such as carbon dioxide mapping of the atmosphere on the earth.
2 micron , High speed photodiode , 90° optical hybrid
Ye, N. 2016. High speed photodiode and 90° optical hybrid for 2 µm optical communication systems. PhD Thesis, University College Cork.