WDM (Wavelength Division Multiplexing) wavelength division multiplexing system mainly provides an easy-to-implement solution for long-distance transmission of high-speed, large-capacity information, and is convenient for transmission expansion of communication networks.
In the traditional optical transmission mode, an optical fiber can only transmit signals of one wavelength at a time, while WDM realizes the transmission of two or more optical wavelength signals on a single optical fiber. WDM mainly realizes the multiplexing and demultiplexing of wavelengths through multiplexers and demultiplexers. At the sending end, the signals of multiple wavelengths are multiplexed together through the multiplexer and coupled to the same optical fiber for transmission; at the receiving end At the end, the optical signals of different wavelengths are separated by the demultiplexer to restore the original signal. The wavelength division multiplexer has the functions of multiplexing and demultiplexing at the same time. In long-distance transmission, in order to enhance the optical signal during transmission, an optical amplifier can also be used in the middle to avoid the weakening of the optical signal during transmission.
The characteristic indexes of WDM include insertion loss, return loss, polarization loss, channel isolation, operating temperature, etc., and the two most important characteristic indexes to be measured are insertion loss and isolation. Insertion loss refers to the attenuation caused by inserting a WDM filter into an optical transmission system, and the lower the insertion loss, the better. Isolation refers to the degree of interference of one channel signal to another channel, and the higher the isolation, the better.
Doubling the transmission capacity. The characteristics of WDM enable it to make full use of the bandwidth resources of optical fibers, and increase the transmission capacity of an optical fiber many times compared with that of a single wavelength. With a channel rate of 10Gbit/s or 2.5Gbit/s, the number of WDM channels can be as high as 32 or more, ensuring that the transmission capacity can reach 300~400Gbit/s.
Good compatibility. WDM has good compatibility with different signals. When transmitting signals of different natures such as images, data and voice, each wavelength is independent of each other and does not interfere with each other, ensuring the transparency of transmission.
On the basis of not changing the basic structure of the existing network, increase the bandwidth as much as possible and increase the data transmission capacity. WDM can be said to be a simple expansion method that can be realized by enterprises.