Wavelength-division multiplexing (WDM) is a technology which allows multiple signals to be transmitted at different wavelengths over a single optical transmission medium. It can dramatically expand the total capacity of an optical network, for many signals are able to be transported simultaneously. This core technology makes optical network capacity to be gradually efficiently increased to meet the higher demand for bandwidth. To construct WDM networks, a wide range of optical components optimized for WDM applications are required to be researched and created. One of the important components is WDM multiplexer.
WDM multiplexer is a electronic device that uses WDM technology. It is able to combine light signals with different wavelengths coming from different fibers on to a single fiber. A multiplexer usually has two signal inputs, one control input and one output. The input end of a WDM multiplexer is coupler that combines all the inputs into one putout fiber. And each channel in a WDM multiplexer is designed to transmit a specific optical wavelength. For example, an 16-channel multiplexer would have the ability to combine sixteen different channels or wavelengths from separate optical fibers onto one optical fiber. And the separated signals will be recovered by another multiplexer called demultiplexer. The following picture shows how the signals are transported.
WDM multiplexer is available with various configurations such as 2,4, 8, 16, 32, 64, etc. The types of multiplexers can be divided by channel spacing. They can be called CWDM multiplexers, wideband or crossband ones, and DWDM multiplexers, narrowband or dense ones. Compared to DWDM multiplexers, CWDM multiplexers combines signals at fewer channels for its larger channel spacing. CWDM multiplexers is usually with configurations such as 8, 16 and so on, while DWDM multiplexers is commonly with configurations including 32, 96, 128, etc. CWDM multiplexers are able to combine a broad range of wavelengths such as l310 nm and 1550 nm. DWDM multiplexers are able to combines wavelengths with 100 GHz channel spacing. It typically provides a broad range of wavelengths in 1.55-μm region within C-band.
WDM multiplexer, an advanced optical component, is widely used in optical links. It can increase connectivity and bandwidth of processing systems by interconnecting different channels. Most WDM multiplexers employ one of three technologies: arrayed waveguide grating (AWG), filter and dispersive element, primarily diffraction grating. Some multiplexers based on filters exhibit high insertion loss for devices with many channels, which makes them are not suitable in the application of multimode and bi-directional transmission. But the multiplexers with AWG technology offers many advantages over them including low cost for many channels, low loss, little crosstalk, and receiving much attention. With AWG technology, WDM multiplexer is ideal for the application of high throughput optical links in parallel processing and computing.
It is concluded that WDM multiplexer with WDM technology is a key component in optical links and even in the high throughput optical links.