Research On The Integrated Demulitiplexing And Receiving Technology Of WDM Systems

The research work in this thesis was supported by grants from one of the sub-projects of National Basic Research Program of China (National "973" Program No.2003CB314901, Prof. Ren Xiao-min as Chief Scientist), New Century Excellent Talents at the University of China (NCET-05-0111) and National High Technology R&D Project (National "863" Project No. 2007AA03Z418).Recently, the increasing demand for bandwidth of telecommunication has greatly promoted the development of optical fiber communications. One of the promising technologies is wavelength-division multiplex (WDM) that has been developed rapidly in the long haul communications. Wavelength-selective receiving has become the key technology of WDM applications. The structure of current demultiplexing receiver is basically "demultiplexer + photodetector" and its performance is not quite well, such as high cost, over-size and additional insertion loss etc. In comparison, the integrated optoelectronic devices can integrate several different optoelectronic components; they can achieve more functions than the devices which are based on the combination of separate components. At the same time, due to a more compact structure, weak optical and electrical connections loss, optical and electrical properties, the integrated optoelectronic devices are more advantages on stability, and reliability, and greatly reduce the cost of the device package.Resonant-cavity-enhanced(RCE) photodetectors is a kind of innovative vertical cavity structure, which integrats demultiplexing and receiving functions in one, with placing a PIN photodetector in Fabry-Perot (F-P) cavity. RCE photodetectors decouples the quantum efficiency (QE) with the carrier transiting time and overcome the tradeoff between QE and response speed lies in conventional PIN photodetectors to some extend. The enhanced effect in resonant wavelengths resulting form resonant cavity enables RCE photodetectors with inherent wavelength selectivity, which is quite attractive for WDM systems. In this thesis, the Integrated Wavelength Demultiplexing Photodetecting Technologies for the WDM are studied.The main research work is listed below:1,Summed up the development of WDM system, the key technologies of WDM application, high-speed photodetectors in optical fiber communications.2,A novel integrated demultiplexing receiver for parallel detecting is proposed, which is analyzed by the method of transfer matrix. An example of this kind of the novel integrated demultiplexing receiver which can detect four light-waves parallelly was designed, the demultiplexing capability is investigated and the cross-talk is calculated. The result demonstrated that the demultiplexing performance of this receiver is preferable, and can be applied in the WDM system.3,In order to get the parallel integrated demultiplexing receiver with the ladder structure, I got four different thickness of the ladder structure by wet etching in the same GaAs substrate, observed the ladder structure of the GaAs substrate, recorded the surface and cross-section micrograph, measured the thickness difference between the ladders, and calculated the etching rate of the H₂SO₄: H₂O₂: H₂O=1: 1: 30 which is about 1.985nm/s. All of that accumulated the experimental experience and data for realizing the controllable ladder cavity successfully.4,In order to improve the structure of OMITMIC, increase the times of reflection in the absorbing cavity, and make the light be absorbed more sufficiently, I studied the fabrication of the curved cantilever. By the way of selected etching, I fabricated the curved cantilevers on the InP substrate, and then measured the sizes of the curved cantilevers by SEM. The curved cantilevers have different angles with different sizes.