Dense wavelength division multiplexing (DWDM) is a wavelength division multiplexing (WDM) technology that expands the transmission capacity of existing optical fiber networks. Save a lot of fiber resources in transmission applications. There are two main types of DWDM systems at present: passive DWDM systems and active DWDM systems.

Passive DWDM System

Active components such as fiber amplifiers and dispersion compensators are not used in passive DWDM systems. The transmission distance of this system will be limited by the transmit power of optical modules, but it has the advantage of high channel capacity and is mainly used in metropolitan area networks and high channel capacity in high-speed transmission lines.

Active DWDM system

Active DWDM is a system that includes transponders that perform optical-electrical-optical (OEO) conversion. In addition, there are multiple erbium-doped fiber amplifiers (EDFA) in the system to ensure that the receiving end can receive high-quality optical signals, but the number of erbium-doped fiber amplifiers (EDFA) will be affected by the fiber type, the number of wavelength channels, Transmission rate, signal-to-noise ratio (OSNR) and other factors.

The link length of an active DWDM system is not only related to the number of fiber amplifiers and the signal-to-noise ratio (OSNR), but also to the dispersion of the optical signal. Therefore, when designing an active DWDM system, the dispersion of the optical signal should be taken into account. If necessary, a dispersion compensator (DCM) can be added to the active DWDM system. It should be noted that the dispersion compensator (DCM) It will increase the insertion loss of the optical fiber link, and will also affect the transmission distance of the active DWDM system.

Passive DWDM System vs Active DWDM System

Passive DWDM systems and active DWDM systems have their own advantages and disadvantages, which will be introduced in detail in this section.

Pros and Cons of Passive DWDM Systems

Cost savings: Compared with active DWDM backbones equipped with fiber amplifiers and dispersion compensators, passive DWDM can build high-speed transmission lines with high channel capacity at a lower cost.

Simple to use: Passive DWDM is a plug-and-play system that is simple and convenient to use.

However, passive DWDM systems also have shortcomings in the following areas:

Scalability: The number of wavelength channels in passive DWDM systems is limited. If you want to expand the network, you must use more passive DWDM devices, which will increase the difficulty of system management.

Advantages and Disadvantages of Active DWDM Systems

Active DWDM systems support a greater number of wavelength channels, resulting in greater bandwidth and higher fiber utilization. In addition, the active DWDM system is easier to manage, users can adjust the channel wavelength online without shutting down the system, and the expansion of the active DWDM system is easier.

Compared with passive DWDM systems, active DWDM systems have longer transmission distances and higher deployment costs. In addition, active DWDM systems also use optical fiber amplifiers, dispersion compensators and other equipment, and their deployment is more complicated than passive DWDM systems.

Concluding remarks

Passive DWDM systems and active DWDM systems have their own advantages, and we should deploy appropriate DWDM systems according to specific application requirements. No matter which of the above systems is deployed, a DWDM multiplexer/demultiplexer is essential.