Passive DWDM System vs Active DWDM System

Dense Wavelength Division Multiplexing (DWDM) is a Wavelength Division Multiplexing (WDM) technology that extends the transmission capacity of existing fiber optic networks. It can multiplex multiple optical carrier signals into a single fiber for transmission, which can save a lot of fiber resources in long distance transmission applications. There are two main types of DWDM systems: passive DWDM systems and active DWDM systems.

Passive DWDM System

Passive DWDM systems do not use active devices such as fiber amplifiers and dispersion compensators. The transmission distance of this system is limited by the transmit power of the optical module, but it has the advantage of high channel capacity and is mainly used in metropolitan networks and high-speed transmission lines with high channel capacity.

Active DWDM System

Active DWDM is a system that contains a transponder, which serves to perform optical-electrical-optical (OEO) conversion. In addition, the system is equipped with multiple erbium-doped fiber amplifiers (EDFAs) to ensure that the receiver receives high-quality optical signals, but the number of EDFAs is limited by the fiber type, 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 affected by the dispersion of the optical signal. Therefore, when designing an active DWDM system, the dispersion of the optical signal should be taken into account, and if necessary, a dispersion compensator (DCM) can be added to the active DWDM system. It should be noted that the dispersion compensator (DCM) will increase the insertion loss of the fiber link, which will also have an impact on the transmission distance of the active DWDM system.

Passive DWDM system and active DWDM system have their own advantages and disadvantages, and this part will introduce them in detail respectively.

Passive DWDM System vs Active DWDM System

Pros and Cons of Passive DWDM System

● Cost savings: Compared to active DWDM backbones equipped with fiber amplifiers and dispersion compensators, passive DWDM enables the construction of high-speed transmission lines with high channel capacity at a lower cost.

● Easy to use: Passive DWDM is a plug-and-play system that is both simple and easy to use.

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

● Scalability: Passive DWDM systems have a limited number of wavelength channels, and if you want to expand the network, you must use more passive DWDM devices, which will increase the difficulty of managing the system.

Pros and Cons of Active DWDM System

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

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

Summary

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