Research On Optical System Of MEMS Variable Optical Attenuator

The networks hierarchy and fundamentals have been running toward high-speed, large-capacity and high-service-quality. Based on DWDM technologies, All Optical Networks make full use of potentially broad bandwidth of optical fiber, and will become the key technologies of information networks. Optical attenuator is an important optical passive component, wide used in optical communication, especially in All Optical Networks.A Variable Optical Attenuator is designed, which is based on 5 voltage driven Micro-electromechanical System; VOA's working wavelength is 1550nm. Besides the good optical performance possessed by traditional VOA, the driven voltage is low, the optical structure is simple, the integration of multi-channels is easily achieved, the ratio of performance and price is high, etc. The optical components include a pigtail with dual fibers, a C-Lens and a MEMS Mirror; its optical structure is very simple. Its basic working principles are the mirror's turn driven by MEMS, the light direction's changes influenced by mirror's positions, gauss-optical-beam's transmitting and the coupling theory.The Optical Attenuator's(OA) uses in AON, the classification of OAs, realization methods of OAs are summarized. The developing process, foreground and research results in and abroad are presented. The researching aim and significance of this project are put forward.MEMS and MOEMS technologies, several MEMS VOAs'structures and principles are introduced. Based on the existing schemes, a novel MEMS VOA is designed; the innovation is adopting a C-Lens with 8 degree tilt. The optical structure and working principles of the MEMS VOA are also given. Based on the existing C-Lens'structure, optical structure requirements of VOA are analysised, the optical components'assembly is gained.The optical structure of the VOA is equivalent to the coupling structure of two single-mode fiber collimators'; using the changes of mirror's tilt, different attenuations are achieved. Basing on fibre optics theory, the coupling of two single-mode fiber collimators is analysised; thus the calculating formulae of Insertion Loss, Attenuation and WDL are achieved. Basing on matrix optics, the calculating formula of Return Loss is gained. The influencing factors of optical parameters are detailed discussed. Concepts of PDL and TDL are given, the optical parameters'requests for optical communication are also given.Finally, experimental research on VOA is carried out, including the design of measure system, the adjusting of optical path, the measurement and research of optical parameters, etc. The results indicate that this scheme of VOA is feasible, IL,Attenuation,PDL,WDL and RL meet the requests of optical communication. The problem is that TDL is not easily controlled. After revision on the scheme and improvement on assembly procedure and skill, expected specifications are reachable.