Study On Key Technologies For 8-Channel Array Of Variable Optical Attenuator Using Polymer-Dispersed Liquid Crystal

With the development of optical fiber communications and applications of Dense Wavelength Division Multiplexing, it is very important to equilibrium the channel power. The optical attenuator is a key device which acts to equilibrium power. It could attenuator the power in the range of the requirement of clients in the optical fiber network. The attenuator can protect the receiver. At present, the variable optical attenuator has some insufficient in the cost, response speed, reliability and miniaturization of integration, and other aspects that can not meet the demand for rapid development of optical communication network requirements. It is a significant research and trends to replace the existing products using some new technologies and new materials and integrated optical attenuator array. They have tremendous market demand.The main research of this thesis is present. Firstly we found out the right polymer dispersed liquid crystal film through changing a series of process conditions, such as content of liquid crystal, polymer to dispersant, content of optical initiator, solidification temperature. We have made a large number of contrast tests and found out the best process conditions of preparing polymer dispersed liquid crystal film. Secondly we used RF magnetron sputtering method to make indium tin oxide (ITO) transparent conductive films as the transparent conductive electrode to control the polymer liquid crystal material by contrasted the electro-optical properties of ITO films under the different experimental parameters. We analyzed and optimized the influence of different craft parameter to the electro-optical properties of the ITO thin film and got the ITO conductive thin films that have high transmittance, high conductivity, surface smooth formation and Uniform distribution. Find out the very experimental parameters with which the prepared films'resistivity combines best with the films'transmittance. Thirdly, we studied and designed the 8-Channel array of variable optical attenuator using polymer disperse liquid crystal and it use the light scattering effect of polymer liquid crystal under the different electric-field intensity, to change the optical path to achieve energy controllable continuous attenuation.The 8-Channel array of variable optical attenuator can create conditions for the practical use of technology and development of theory.The VOA array based on Si (100) crystal that we used its anisotropic etching characteristics in KOH solution to make self-aligned positioning groove array and electrode array, liquid crystal micro-box structure. The whole device has compact size, simple fabrication processes, and low cost. The several main attenuation Performance Parameters of the liquid crystal polymer Variable Optical Attenuator have insertion loss, return loss and response time . Atλ=1.5μm we tests the open-voltage for 2.9 V_rms, the threshold has good properties, driving voltage range of 2.9 V_rms-21.9V_rms; The best insertion loss is 5.27 dB; Attenuation range is 5.27 dB - 18dB; Return loss is 37 dB; Crosstalk of all channels is more than 50dB.The VOA array based on resin consist of fiber collimators assembled in parallel V-shaped grooves onto a piece of plastic and liquid crystal cell that gap is d=8μm and we could drive ITO electrode to control the polymer disperse liquid crystal material. The whole device has low cost and suited assembled. Tests of the fabricated VOA are carried out. It is presented that the open-voltage for 2 V_rms, the threshold has good properties, driving voltage range of 2(V_rms-21V_rms; The best insertion loss is 3.98 dB; Attenuation range is 3.98 dB– 19.4dB; Return loss is 40 dB; Crosstalk of all channels is more than 50dB.Our attenuator has the advantages such as a small and exquisite volume, low costs, being apt to realize many arrays of the devices. This technology overcomes the shortcoming of the traditional optical attenuator such as bulky, complicated process, difficult to integrate, without polarizer, does not require special orientation processing and has relatively simple structure.