Research On The Error Characteristics Of Multi-Wavelength Multi-Level Optical Storage With Photochromic Materials

Multi-wavelength multi-level (MWML) optical storage withphotochromic materials is one of the most important techniques to increasethe capacity of optical systems without change the NA of optical system. Withproviding more choices for the ECC, MWML brings more new problems forthe optical storage, such as error characteristics. Researches on the errorcharacteristics of MWML optical storage with photochromic materials arecarried out, A new error correcting method for the MWML optical storagewith photochromic materials is put forward based on the error characteristics.The main contents include:The theoretical model of the relations between the index of reflectivitywith the thickness, the sensitivity, the concentration of photochromicmaterials, writing power and writing time is set up according to thephotochemical theory. The relations between error rate and variations in thethickness of photochromic materials is studied by setting up the relationsbetween variations in the index of reflectivity and variations in the thicknessof photochromic materials. The variations in the thickness of photochromicmaterials of 650nm, 780nm and 532nm must be controlled in the range of2.5% to meet the commands of 8 level storage.The relations between crosstalk with error rate are studied by researchthe writing and reading model of MWML optical storage with photochromicmaterials. The crosstalk of 650nm, 780nm and 532nm must be controlled inthe range of 3% to meet the commands of 8 level storage. These are verifiedby experiments.The error characteristics of optical channel are studied by analysis SDR.A new error correcting method for the MWML optical storage withphotochromic materials is put forward based on the error characteristics. Themulti-wavelength and multi-level are all transformed to multi-layers. RS-PCerror correcting code is used, combining with using error correct and erasurecorrect method, according to the relations between each layer. The capacity ofinformation is improved by 6% for three-wavelength 8 level optical storage byusing this method, comparing with normal error correcting mode.