As we all know, DWDM technology can transmit dozens of wavelengths in a single optical fiber, which greatly expands the transmission capacity of optical fiber communication systems. The earliest wavelength division multiplexing/demultiplexing module used in the DWDM system is based on the dielectric film filter TFF. Both of these are in series structure. Different wavelengths experience different numbers of devices in the module, resulting in different power losses. As the number of ports increases, the loss uniformity of the DWDM module deteriorates. At the same time, the maximum loss at the last port is another factor that restricts the number of ports. Therefore, the number of channels of DWDM modules based on TFF technology usually does not exceed 16.
However, a typical DWDM system usually transmits 40 or 48 wavelengths in a single optical fiber, so a multiplexer/demultiplexer with a larger number of ports is required. The WDM module of the series structure will accumulate too much power loss in the rear port, so it is necessary to adopt a parallel structure to multiplex/demultiplex dozens of wavelengths at a time. Arrayed waveguide grating AWG is such an optical device.
The working principle of AWG:
The working process of AWG can be regarded as the same: DWDM signal is input from the center position C of the output waveguide, and is distributed to the arrayed waveguide through free transmission in the output star coupler; multiple beams are transmitted to the mirror surface on the right half of the arrayed waveguide, The reflected multiple light beams enter the output star coupler; after free transmission in the star coupler, light beams of different wavelengths are focused on different positions and received by the output waveguide, thereby realizing the demultiplexing of the DWDM signal.
The main application of AWG
Wavelength routing: When an optical signal passes through a network node, it is routed according to its wavelength, without photoelectric conversion. The wavelength determines the path of optical signal transmission, realizes wavelength reuse, and improves wavelength utilization.
LED spectrum division multi-wavelength light source: Use AWG to divide the wide-spectrum light of the LED to obtain a low-cost multi-wavelength light source for use in WDM-PON (wavelength division multiplexing passive optical network)
Optical add/drop multiplexer: At the connection point of the optical signal network, it is often necessary to "divide" part of the signal stream from the node, or "plug" some signal stream into the network transmission system. This kind of equipment that can separate the signal and insert it is called an "optical add/drop multiplexer".
Optical cross interconnection: The optical cross interconnection is mainly used to complete the cross connection between multi-wavelength ring networks, as the node of the grid optical network, and the purpose is to realize the automatic configuration, protection, restoration and reconstruction of the optical wave network.
All-optical transmission network: In the all-optical network structure and all-optical transmission network, OXC and OADM play the role of information transmission and cross interconnection.