The resulting increase in transmission rates attributed to Factors such as new applications, changing patterns of usage, and redistribution of contents caused mainly by wide acceptance of the Internet, many carriers are finding that their estimates of fiber needs have been highly underestimated. With these explosive growth in Bandwidth demand and customer expectations is in a state of ongoing evolution.DWDM is sometimes called wave division multiplexing (WDM) and WDM is growing denser as the technology evolves. moreover, these two terms are often used synonymously. WDM is a technology that increases the data-carrying capacity of optical fiber by allowing multiple streams of data to be transported using different wavelengths of light whereas ,Dense Wavelength Division Multiplexing (DWDM) is applied to the WDM process when multiple wavelengths of light signals are involved. DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber.

DWDM Revolutionized data transmission technology by increasing the capacity signal of embedded fiber. The recent explosion of DWDM technology forced the fiber optic manufacturers to develop DWDM multiplexers and demultiplexers that can handle closely spaced optical wavelengths. Although Dense Wavelength Division Multiplexing (DWDM) are usually considered third choice by providers. DWDM infrastructure are  designed to provide a graceful network evolution for service providers who seek to address their customers’ ever-increasing capacity demands. The technical requirement is only that the lasers be of very specific wavelengths and the wavelengths are very stable, and the DWDM demultiplexers capable of distinguishing each wavelength without crosstalk. Dense Wavelength Division Multiplexing (DWDM) is an optical multiplexing technology used to increase bandwidth over existing fiber networks. Therefore, it is a much less expensive option for expanding network capacity compared to installing additional fiber cables.DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber. The technology creates multiple virtual fibers, thus multiplying the capacity of the physical medium.

In addition, DWDM has some significant advantages over CWDM. DWDM combines multiple optical signals so that they can be amplified as a group and transported over a single fiber to increase capacity (see Figure 3). Each signal carried can be at a different rate (OC−3, −12, −24, etc.) and in a different format (SONET, ATM, data, etc.) For example, a DWDM network with a mix of SONET signals operating at OC–48 (2.5 Gbps) and OC–192 (10 Gbps) over a DWDM infrastructure can achieve capacities of over 40 GbpsThis unifying capability allows providers to offer services such as e-mail, video, and multimedia carried as Internet protocol (IP) data over asynchronous transfer mode (ATM) and voice carried over SONET/SDH. A key advantage to DWDM is that it’s protocol- and bit-rate-independent. In effect, allows the service provider the flexibility to respond to customer demands over one network.

The primary benefit of DWDM structure one fiber is transformed into multiple virtual fibers. When your project consists of a longer distance than 10 kilometers and you want to future proof or you’re already planning to use more than 18 times 10 Gigabit; In addition to technological constraints,DWDM is your preferred technique.This systems also maintain more stable wavelength or frequency than those needed for CWDM because of the closer spacing of the wavelengths.

Nevertheless , since DWDM provides greater maximum capacity it tends to be used at a higher level in the communications hierarchy than CWDM. Dense wavelength division multiplexing (DWDM) is wavelength division multiplexing (WDM) with typical channel spacing of 100 GHz for 40 channels and 50 GHz for 80 channels. Each channel contains a TDM (time division multiplex) signal. And each of up to 80 channels can carry 2.5 Gbps for a total of 200 billion bits per second by the optical fiber.

Note: Recent innovations in DWDM transport systems include pluggable and software-tunable transceiver modules capable of operating on 40 or 80 channels.

Keywords:CWDM Coarse Wavelength Division Multiplexing, DWDM Dense Wavelength Division Multiplexing, WDM Wavelength Division Multiplexing