Specifications of types of wdm in optical communication

Wavelength division multiplexing in computer networks

The main results are as follows: (1) make full use of the low loss band of optical fiber to increase the transmission capacity of optical fiber, so that the physical limit of transmitting information in an optical fiber can be doubled to several times. 

We only make use of a very small part of the optical fiber low loss spectrum (1310nm-1550nm). Wavelength division multiplexing can make full use of the huge bandwidth of single-mode fiber about 25THz, and the transmission bandwidth is sufficient. 

(2) dwdm dense wavelength division multiplexing has the ability to transmit two or more non-synchronous signals in the same optical fiber, which is conducive to the compatibility of digital and analog signals, independent of data rate and modulation mode, and can flexibly take out or add channels in the middle of the line. 

(3) for the wavelength division multiplexing in optical fiber, especially for the optical cable with a small number of cores laid in the early stage, as long as the original system has power margin, it can further increase the capacity and realize the transmission of multiple one-way or two-way signals without making major changes to the original system. It has strong flexibility. 

(4) because the use of optical fiber is greatly reduced, the construction cost is greatly reduced, and because the number of optical fiber is small, it is also rapid and convenient to recover when there is a failure. 

(5) the sharing of active optical equipment, the transmission network telecom of multiple signals or the increase of new services reduce the cost. 

(6) the active equipment in the system is greatly reduced, so the reliability of the system is improved.

Development of wavelength division multiplexing in computer networks

With the rapid development of optical fiber communication, optical communication network has become the basic platform of modern communication network. 

The optical fiber communication system has gone through several stages of development, from the PDH system in the late 1980s, the SDH system in the mid-1990s, the WDM system and the optical fiber communication system to the rapid upgrading. 

Dual-wavelength WDM (1310/1550nm) system was used in American AT&T network in 1980s at a rate of 2 × 17Gb/s. 

The WDM technology is applied to transfer the multiplexing mode from the electrical signal to the optical signal for the first time, and the transmission rate is improved by wavelength division multiplexing (that is, frequency multiplexing) in the optical domain. The optical signal is directly multiplexed and amplified, and each cwdm wavelengths is independent of each other and transparent to the transmitted data format. 

One of the hotspots of current research is that the DWDM,DWDM laboratory level can reach 100 km 10Gbit/s, the relay distance is 400 km 40Gbit/s, the relay distance is 85 km, the relay distance is 64 km 5Gbit/s, and the relay distance is 720km. 

The commercial level of dense wavelength division multiplexing (DWDM) is 320Gbit/s, that is, a pair of optical fibers can transmit 4 million sessions. At present, the transmission capacity of commercial systems is only 1Tbit / s, which can be transmitted by a single optical fiber.

Why is ultiplexer used in optical fibre?

There are types of wdm in optical communication, and the imaging result of the multiplexer in optical fiber is that wavelength division multiplexing (WDM) is an optical fiber transmission technology that uses multiple optical wavelengths to transmit data on the same medium. In order to ensure the stable operation of the dense channel system, high-precision filters are needed to peel off specific wavelengths without interfering with adjacent wavelengths. In fact, the next generation of coherent modems of wavelength division multiplexing applications are smart enough to consider a wider variety of constellation and baud rate options to achieve excellent tunability. The dwdm in optical communication must also use a precision laser operating at a constant temperature to keep the channel at the target position.