Dense Wavelength Division Multiplexing (DWDM)

Dense Wavelength Division Multiplexing (DWDM) is a fiber-optic transmission technique. It involves the process of multiplexing many different wavelength signals onto a single fiber. So each fiber have a set of parallel optical channels each using slightly different light wavelengths. It employs light wavelengths to transmit data parallel-by-bit or serial-by-character. DWDM is a very crucial component of optical networks that will allow the transmission of data: voice, video-IP, ATM and SONET/SDH respectively, over the optical layer.

From both technical and economic perspectives, the ability to provide potentially unlimited transmission capacity is the most obvious advantage of DWDM technology. The current investment in fiber plant can not only be preserved, but also optimized by a factor of at least 32. As demands change, more capacity can be added, either by simple equipment upgrades or by increasing the number of lambda’s on the fiber, without expensive upgrades. Bandwidth aside, DWDM’s technical advantages are transparency, scalability and dynamic provisioning.

DIGITALWATERMARKING

The growth of high speed computer networks has explored means of new business, scientific, entertainment, and social opportunities. Digital media offer several distinct advantages over analog media, such as high quality, easy editing, high fidelity copying. The ease by which digital information can be duplicated and distributed has led to the need for effective copyright protection tools. Various software products have been recently introduced in attempt to address these growing concerns. It is done by hiding data within digital audio, images and video files. One way such data hiding is copyright label or digital watermark that completely characterizes the person who applies it and, therefore, marks it as being his intellectual property. Digital Watermarking is the process that embeds data called a watermark into a multimedia object such that watermark can be detected or extracted later to make an assertion about the object. Watermarking is either visible or invisible. Although visible and invisible are visual terms watermarking is not limited to images, it can also be used to protect other types of multimedia object.

Direct sequence code division multiple access (DS-CDMA)

The ordinary CDMA technology has the disadvantage of identifying the users using the appropriate signature of each user. Since many users tend to use the transmission media, there is always a chance for superimposition of signals that can cause interference in network.

The solution for this inconvenience comes in the form of interleaving which separates the users. This special form of CDMA technology offers some of the features of CDMA such as the dynamic channel sharing, mitigation of cross cell reference, asynchronous transmission, ease of cell planning and robustness against fading, apart from the low cost interference cancellation technique available for systems with large number of users in multi path channels. Available with the second and third generation mobile phones, the cost per user of this algorithm is independent of the number of users. Giving a better performance along with the simplicity in usage it can maintain it’s low complexity and high performance even in multi path situations too.

dynode

A dynode is one of a series of electrodes within a photomultiplier tube. Each dynode is more positively charged than its predecessor. Secondary emission occurs at the surface of each dynode. Such an arrangement is able to amplify the tiny current emitted by the photocathode by typically one million.

DLP Projector

DLP Projector is an optical system driven by digital electronics. Its the only display solution that enables movie video projectors, televisions, home theater systems and business video projectors to create an entirely digital connection between a graphic or video source and the screen in front of you. At the heart of every DLP projection system is an optical semiconductor that manipulates light digitally known as the Digital Micromirror Device, or DLP chip which is a rectangular array of up to 2 million hinge-mounted microscopic mirrors( each of these micro mirrors measures less than one-fifth the width of a human hair. When a DLP chip is coordinated with a digital video or graphic signal, a light source, and a projection lens, its mirrors can reflect an all-digital image onto a screen or other surface. It has three key advantages over existing projection technologies. The digital nature of DLP enables digital gray scale and color reproduction and also positions DLP to be the final link in the digital video infrastructure. Because it is based on the reflective DMD, DLP is more efficient than competing transmissive LCD technologies. Finally, DLP has the ability to create seamless, film like images. DLP makes images look better. You\'ve heard the digital revolution, now see it with Digital Light Processing.

Need more information mail me or download this
http://www.infocomm.org/cps/rde/xbcr/infocomm/ProjectorTechnologyExplained.pdf
http://www.xilinx.com/esp/broadcast/collateral/projectors.pdf

Digital T.V

Broadcasters are concerned with many in-band and out-of-band transmission parameters, including data signal quality, clock tolerance, radiated power tolerance, carrier phase noise, adjacent channel emissions, and precision frequency offset requirements. The FCC permits DTV power-level changes and/or transmitting antenna location and height and beam tilt in the context of de minimise interference levels. The Advanced Television System Committee (ATSC) has provided guidelines for broadcasters in the form of suggested compliance specifications, which will be covered in this paper. On December 24, 1996, the FCC adopted the Advanced Television System Committee (ATSC) system (minus video formats) as the new digital television standard for the U.S. Shortly thereafter, on April 3, 1997, the FCC issued its rules for digital operation as well as its first set of channel allocations, loaning each U.S. broadcaster a second 6 MHz channel for digital television transmission. Subsequently, a revised set of allocations was issued in March 1998 with additional rules and changed rules, including a new transmission emission mask and potential increased transmission power provided new de minimise interference criteria are met. Terrestrial digital (DTV) broadcasting is now underway in the major markets in the United States after the Federal Communications Commission (FCC) in several Reports and Orders set the standard on December 24, 1996, and subsequently released rules of operation and broadcaster channel allocations. DTV broadcasters are mainly concerned about the in band and out of band parameters. The in-band parameters describe the signal quality. The important in-band parameters are spectral shape, data pulse shape, data eye pattern, transmitted power specifications etc. The out of band parameters include rigid TV emission mask, NTSC weighted out of band power, DTV un-weighted out of band power, beam tilt techniques etc.