Research On Key Devices And Technologies Of Reconfigurable Optical Add/Drop Multiplexer

With the rapid progress in society and technology, the information service requirements are increasing steadily, the society depend more and more on information resources. The developments of intelligent optical network characterized by All-optical signal processing and broad bandwidth information service represented by FTTH are accelerating. The next generation optical communication system with characteristics of intelligence, integration, low cost and high dependability is under developing.Optical Add/Drop Multiplexer and optical cross-connecter, which is composed of passive and active devices, are the most important part of all-optical network. Compared with the discrete optoelectronic devices, integrated optoelectronic devices have the advantages of ultra-high speed, multifunction, low noise, compact size, higher reliability, lower parasitic parameter, lower cost and so on. Therefore, integrated photoelectronic devices and components are very significant and have drawn a great interest in the optical communication field.The research in this paper is supported by grants from The National Basic Research Program of China (973 Program, No.2003CB314900), The National High Technology Research and Development Program of China (863 Program, No.2007AA03Z418), Program for Changjiang Scholars and Innovative Research Team in University (No.IRT0609) and the 111 Project (No. B07005).This dissertation focuses on key devices and technologies of Reconfigurable Optical Add/Drop Multiplexer (ROADM). The theory and fabrication of key components and tapered micro structure are discussed. In order to achieve integrated ROADM device with good performance, the optimization of the key components and integrated technology using tapered waveguide were investigated. Waveguide integrated optical switch, the tapered waveguide used in waveguide integrated device and InP based semiconductor laser were theoretically and experimentally researched in detail. The contents of this dissertation are summarized as follows:The technology and key components of ROADM were introduced detailed, including the types, fundamental principle and development state of optical switch, tapered waveguide, semiconductor laser, photodetector, and multiplexer/demultiplexer The ROADM based on PLC technology were analyzed and the ROADM scheme with demultiplexer/switch/multiplexer architecture was proposed.An InGaAsP/InP 2x2 Mach-Zehnder interferometer (MZI) optical switch based on multimode interference (MMI) couplers was presented, the basic principle of switch and the carrier modulation on the principle of injection free carriers and bend-filling effects were analyzed. The parameters design and switch characteristic simulations were carried out using beam propagation method. The switch structure was designed to be insensitive to polarization and can be easily integrated with other devices. The optimized configuration parameters provided a theoretical basis for device fabrication.The 2×2 MZI optical switch was studied experimentally according to the designed parameter. The fabrication processes were introduced, including design of mask, epitaxial growth, processing step and so on, and the improvements of critical process were summarized. The device performance was tested, and the results showed that the light signal can be switched from cross port to bar port with an injection current of 43mA. The measured crosstalk is-19.2dB and-14.3dB at the on and off state, respectively. This optical switch can be easily integrated with other active devices and has potential application in future DWDM and OXC systems.The integrated approach of waveguide and photodetector was investigated. A vertically tapered coupling waveguide was introduced in integrated PIN photodiode based on asymmetric twin-waveguide. The mode profiles of the vertically tapered waveguide were simulated at several different positions along the taper. According to a beam propagation method simulation, the coupling characteristics of the vertical tapered waveguide were calculated, the influences of the different refractive index as well as the taper structure parameters on the coupling characteristic were discussed. The different manufacturing methods were introduced. Compared with laterally tapered waveguide, vertically tapered waveguide can achieve high coupling efficiency with shorter taper length. The proposed model is valuable in the design of compact optoelectronic integration device.Taking 1.55μm InP based quantum well laser for example, the fabrication technology of semiconductor laser was investigated in depth. The technologies were mastered from material growth to fabrication. The continue wave operation of the quantum well laser is realized at room temperature.The difficulties in the experiment were discussed in detail. The structure of quantum dots laser was designed. The study progress of (B)InAs/GaAs quantum dots material growth with MOCVD technology were introduced. This study established the technologic foundations of large scale, high performance photoelectronic integrated chip,1.55μm Si based InP material systems laser and long wavelength (B)InAs/GaAs quantum dots laser. It is of great meaning for our group to complete the 973 project.