25-08-2017, 09:32 PM
Dense wavelength division multiplexing has been developed for satisfying the growing demands in bandwidth. When there was a revolution in the high bandwidth application an explosive growth of the internet, this created the capacity demands that exceeded traditional TDM limits. As a result the once seemingly inexhaustible bandwidth from deployment of optical fiber was exhausted. Dense Wavelength Division Multiplexing is a fiber optic transmission technique. It involves the process of multiplexing many different signals onto a single fiber. So such fiber has a set of parallel optical channels using slightly different light wavelengths. It employs light wavelengths to transmit data parallel-by-bit or serial-by-character. DWDM technology utilizes composite optical signals carrying multiple information streams, each transmitted on distinct optical wavelengths. The DWDM could increase throughput to an astronomical 40Gbps on a single fiber. This cutting technology will meet the next generation of bandwidth demand at a significantly lower cost than installing new fiber.Holographic memory is developing technology that has promised to revolutionaries the storage systems. It can store data upto 1 Tb in a sugar cube sized crystal. Data from more than 1000 CDs can fit into a holographic memory System. Most of the computer hard drives available today can hold only 10 to 40 GB of data, a small fraction of what holographic memory system can hold. Conventional memories use only the surface to store the data. But holographic data storage systems use the volume to store data. It has more advantages than conventional storage systems. It is based on the principle of holography. Scientist Pieter J. van Heerden first proposed the idea of holographic (three-dimensional) storage in the early 1960s. A decade later, scientists at RCA Laboratories demonstrated the technology by recording 500 holograms in an iron-doped lithium-niobate crystal and 550 holograms of high-resolution images in a light-sensitive polymer material. The lack of cheap parts and the advancement of magnetic and semiconductor memories placed the development of holographic data storage on hold.