Theoretical And Application Research On Active Vertical Coupler Based 4×4 Optical Crosspoint Switch Matrix

Optical switching, as the key technology of the optical network, is playing an improtant role in optical communication system. Over recent years, the Photonics Group in Bristol has been developing a nanosecond monolithically integrated electrically controlled 4×4 active vertical coupler (AVC) based optical crosspoint switch (OXS) module, which has some advantages compared with other switching devices. In this thesis, the switching performance of the OXS matrix are characterised and the inherent functionalities of the device are explored. With these understandings, several novel application scenarios have been demonstrated.Firstly the coupled mode theory is introduced to easily understand the switching process of Crosspoint. Based on it, the design of the device is described including the structure of the waveguide and the wafer. Through simulated by FIMMWAVE, the important parameters of the device are optimized and used to the design and fabrication process. The fabrication, the packaging and the switching performance are also introduced.The optical label detection system is demonstrated then. Through the receiver and control part of the 155Mbps optical label signal, the corresponding switch cells are open or close. The whole system and the electrical control part are discribed in detail and the Bit-Error Ratio (BER) characteristics are shown in the experimental results. Automatic per-packet power equalisation control is studied based on the provious idea. The experiment results show that the Crosspoint switch is suitable for the optical packet switch and optical power equalisation control.By further exploring the inherent characteristics of the advanced modulation formats such as RZ and RZ-DPSK, the different results are analysized by using the different modulation formats. It is concluded that using the advanced modulation technology could enhance optical signal robustness, receiving sensitivity and the BER characteristic.Owing to the unique design of Crosspoint, it could accomplish lossless multicast technology indenpentently, which equal to integrate the optical switch, splitter and amplifier to a single device. Different multicast scales are inversitaged from 1×2,1×4,2×4 to 4×4 which is the full operation of Crosspoint. The switching characteristics, switched signal quality and OSNR have been investigated when the injection currents of different switching cells are changed in different configurations. The measured results confirm the excellent multicast switching characteristics nearly free from power splitting loss in this device.It is necessary for the optical switching node to accomplish the function of optical buffer and time-slot assignment. A novel optical buffer with a large variable delay range based on Crosspoint switch is proposed and experimentally demonstrated. The power penalty is still small even if the loop number achieves to 9. Based on this good BER characteristic, the variable delay range could be achieved from 1 to 999 time slots in our scheme and, correspondingly, the length of time slot is flexible. By using this novel optical buffer scheme, time-slot assignment functions including time-slot interchange, serial-to-parallel and parallel-to-serial conversion, and optical compressor could be realized. The expermental results show the feasibility and practicability of this novel optical buffer provided with the long-tuned length and simple structure.