Overview of WDM Network

WDM networks are networks that deploy optical WDM fiber links where each one carries multiple wavelength channels. WDM is the acronym of Wavelength Division Multiplexing, which is a technology that multiplexes several signals over a single optical fiber by optical carriers of different wavelengths which use a laser or a LED. There is a multiplexer and a demultiplexer at the either end of the WDM. A multiplexer is at the transmitting end to combine several signals together, and a demultiplexer is at the receiving end to split the signals apart. WDM systems are popular in fiber optic network as they allow to be expanded by simply upgrading the multiplexer and demultiplexer at each end. And with the help of WDM, there is no need for us to overhaul the backbone network regardless of several generations of technology development.

Types of WDM

According to the differences of channel space, there are mainly two kinds of WDM techniques. One is DWDM and the other is CWDM. DWDM is the abbreviation of Dense Wavelength Division Multiplexing, which is a technology that can put data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. DWDM has so dense wavelength intervals that it can multiplex more than 80 separate wavelengths or channels of data into light stream transmitted on a single optical fiber. Each channel can carry 2.5Gbps light signals, and up to 200 billion bits can be delivered a second by the optical fiber. Therefore, DWDM can maintain a more stable wavelength than CWDM and it can be used for long distance optical transmission. But it is a high-cost device and energy consumption that it is not suitable for ordinary people.

CWDM (Coarse Wavelength Division Multiplexing) is an economical technology to save fiber resources through transmitting multiple wavelengths on one optical fiber and it is a multiplexing technology for city and access network. Transmission is realized using five or six wavelengths between 1270nm and 1610nm with a 20nm interval. CWDM is a low-cost system because of its uncooled modulating laser which only consumes 0.5W power, and its cost only takes up 30% of the DWDM expense. Therefore, CWDM is available for the applications in a short distance, high bandwidth and areas with dense access points. It can be used in cable television networks, where different wavelengths are applied for the downstream and upstream signals.

Commonly Used Devices in WDM Network

Optical Splitter

Today, network technology develops fast, the advent of fiber optic splitter is magnificent in helping users maximum the performance of optical network circuits. Fiber optic splitter also called as beam splitter is used in passive optical network (PON) which can split an incident light beam into two or more light beams, and vice versa. It is suitable for the maintenance of long-haul network, cable TV ATM circuit or local area/metro area network, and it also can be used for FTTx/PON applications. Generally, PLC splitter and FBT splitter are the two commonly used types.

Optical Amplifier

With the demand for longer transmission length, optical amplifiers have become an essential component in long-haul fiber optic systems. An optical amplifier is a device which can amplify an optical signal directly, without the need to convert it to electricity signal first. It may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed. Optical amplifier can be used in both linear and non linear modes of operation. Commonly used types of optical amplifier are semiconductor laser amplifiers and fiber amplifiers.

Optical Attenuator

In data communication, receiving either too much or too little optical power will cause high bit error rates. In order to solve this problem, using an optical attenuator is a good solution. An optical attenuator is a passive device used to reduce the power level of an optical signal either in free space or in an optical fiber without appreciably distorting the waveform. Optical attenuator is widely used in fiber optic communications, either to test power level margins by temporarily adding a calibrated amount of signal loss, or installed permanently to properly match the levels of a transmitter and receiver. There are two commonly used types, including fixed attenuator and variable attenuator.

CWDM Mux/Demux

CWDM Mux/Demux is a passive device which is very reliable and simple to use. These devices are available with various of wavelength combinations, usually from 1270nm to 1610nm with 20nm intervals. And based on different applications, a CWDM Mux/Demux module can be designed into different channels. A typical four channel Mux/Demux module can be used to multiplex four different wavelengths onto one fiber which means four different data can be transmitted over the same fiber at the same time. And Mux/Demux modules are integrated in an entirety. In general, CWDM Mux/Demux products can be used in fields, like all enterprises and carrier with fiber optic infrastructure, connecting field offices to central office, and so on.

DWDM Mux/Demux

DWDM Mux/Demux is designed to multiple DWDM channels into one or two fibers. The common configuration is 4, 8, 16, and 40 channels, or 50G DWDM Mux/Demux. These modules multiplex the light signal outputs from four or more electronic devices passively and send them over a single optical fiber, then demultiplex the signals into separate, distinct signals for input into electronic devices at the end of the fiber optic link.

WDM network is an important part in fiber optic communication, and there are a number of devices in a WDM network. This is a brief introduction about WDM network in this article. Hope it can give users a general knowledge of WDM network.