The Key Technology Of Liquid-core Tunable Filter Key Technology

Currently, with the rapid development of science and technology application,optical wavelength division multiplexing technology has been developed considerablyin optical communications. In a WDM system, using a wavelength selection controland select the channel, which is equivalent to the control information transmission.The tunable optical filter can realize the selection and control of the wavelength oflight, so it is important for the development of optical communications. Based onmultimode interference principle, this paper proposes a liquid core tunable filterstructure and confirms the feasibility of the structure by two aspects of the theoreticalsimulation and experiment。Firstly, multimode interference tunable filter structure is studied intensively,based on the full analysis of the development status of the optical filter at home andabroad. This paper builds mathematical modeling of single mode-multimode-single-mode fiber interference filter structure and analyses the interference Self-focusingeffect and characteristics of Interference filter on the structure.Secondly, based on the simulation of the single mode-multimode-single modefiber-optic interferometer, the paper proves the drift of the transmission spectrumcenter wavelength, when changing the length of multimode optical fiber in the filterstructure. Changing the length of the multimode fiber in the experiment, experimentalresults identify with the simulation results that is the output spectrum centerwavelength appears blue shift, when increasing the length of the multimode opticalfiber.Lastly, a filter structure that is a single mode-multimode-single mode fiber-optictunable reflective filter structure is realized by using liquid-filled capillary instead ofmulti-mode fiber and high reflectivity of the mercury. Because the liquid in thecapillary is a linear relationship with the temperature, the filter structure can be tunedby changing temperature in the experiments. So the changing rate of the outputspectrum center wavelength is obtained.