We know that DWDM technology can transmit dozens of wavelengths in a single fiber, which greatly expands the transmission capacity of optical fiber communication system. The earliest MUX/DEMUX module in DWDM system is based on dielectric membrane filter TFF. Both of these are series structures, with different wavelengths experiencing different numbers of devices in the module, resulting in different power losses. As the number of ports increases, the loss uniformity of DWDM modules deteriorates. At the same time, the maximum loss at the end of the port is another factor limiting the number of ports. Therefore, the channel number of DWDM module based on TFF technology is usually no more than 16.

   However, a typical DWDM system typically transmits 40 or 48 wavelengths in a single fiber, thus requiring a larger number of ports MUX/DEMUX. A series WDM module will accumulate too much power loss in the rear ports, so it needs to adopt a parallel structure to MUX/DEMUX tens of wavelengths at one time. Array waveguide grating AWG is one such optical device.

   Array waveguide gratings are usually used in Optical Multiplexers (DE) of WDM systems. These devices can compound light of many wavelengths into a single fiber to improve the propagation efficiency of Optical fiber networks.

The structure of the AWG

    A typical AWG structure consists of an input waveguide, an input star coupler (free transmission region FPR), and an array of waveguides, an output star coupler, and dozens of output waveguides. The length of the waveguide array is in an arithmetic series. The length of the first waveguide is L0, and the length of i waveguide is Li. The DWDM signal enters the input star coupler from the input waveguide and is distributed to the waveguide array after free transmission. The assignment process is wavelength independent and all wavelengths are assigned to the array waveguide indiscriminately. Array waveguide produces phase difference for multiple beams, and the phase of each beam is in an arithmetic series, which is similar to the situation in traditional grating. The different wavelengths are dispersed and focused at different locations in the output star coupler. Different wavelengths are received by different waveguides, so parallel DEMUX of DWDM signals is realized.

   Array waveguide grating (AWG) is a key component of DWDM networks which are developing rapidly. AWG can obtain a large number of wavelengths and channels, realize the multiplexing and DEMUX of tens to hundreds of wavelengths, and can flexibly form multifunctional devices and modules with other optical devices. High stability and excellent cost performance are also one of the reasons why AWG is the preferred technology for DWDM.