An Overview of DWDM Technology & Network

This article covers functions and applications of DWDM system components. The operation of each component is discussed individually. DWDM terminology like Attenuation, dispersion, and optical signal to noise ratio (OSNR) are measures of optical signal quality and are the key factors involved in DWDM system design and operation. From transmitter to receiver, the quality of the optical signal and the path across which it travels determines if it is successfully detected and recovered at the receiving end. A description of each type of signal measure and its relationship to a DWDM system is given. Index Terms— Dense wavelength division multiplexing (DWDM),Optical transmitters/receivers, DWDM mux/demux filters.Optical add/drop multiplexers (OADMs), Optical amplifiers, Transponders (wavelength converters), Attenuation, dispersion, and optical signal to noise ratio. —————————— a —————————— 1 I ense wavelength division multiplexing (DWDM) is an extension of optical networking. DWDM devices com- bine the output from several optical transmitters for transmission across a single optical fiber. At the receiving end, another DWDM device separates the combined optical signals and passes each channel to an optical receiver. Only one opti- cal fiber is used between DWDM devices (per transmission direction). Instead of requiring one optical fiber per transmitter and re- ceiver pair, DWDM allows several optical channels to occupy a single fiber optic cable.A key advantage to DWDM is that it's protocol and bit-rate independent. DWDM-based networks can transmit data in IP,ATM,SONET, SDH and Ethernet .Therefore, DWDM-based networks can carry different types of traffic at different speeds over an optical channel.Voice transmission, e-mail, video and multimedia data are just some examples of services which can be simultaneously transmitted in DWDM systems.DWDM systems have channels at wave- lengths spaced with 0.4 nm spacing.DWDM is a type of fre- quency division multiplexing (FDM). A fundamental property of light states that individual light waves of different wave- lengths may co-exist independently within a medium. Lasers are capable of creating pulses of light with a very precise wa- velength. Each individual wavelength of light can represent a different channel of information. By combining light pulses of different wavelengths, many channels can be transmitted across a single fiber simultaneously. Fiber optic systems use light signals within the infrared band (1mm to 400 nm wave- length) of the electromagnetic spectrum. Frequencies of light in the optical range of the electromagnetic spectrum are usual- ly identified by their wavelength, although frequency (dis- tance between lambdas) provides a more specific identifica- tion.