PDF of this tutorialThere are certain key characteristics of acceptable and optimal DWDM systems. These characteristics should be in place for any DWDM system in order for carriers to realize the full potential of this technology. The following questions help determine whether a given DWDM system is satisfactory.
Does the system reuse embedded equipment and fiber plant?
DWDM systems at 2.5 Gbps should use the full capability of the embedded equipment and fiber base.
Is the system robust and reliable?
Well-engineered DWDM systems offer component reliability, system availability, and system margin. Although filters were often susceptible to humidity, this is no longer the case.
Do the pump lasers have connectors, or are they spliced in the optical amplifier?
An optical amplifier has two key elements: the optical fiber that is doped with the element erbium and the amplifier. When a pump laser is used to energize the erbium with light at a specific wavelength, the erbium acts as a gain medium that amplifies the incoming optical signal. If a connector is used rather than a splice, slight amounts of dirt on the surface may cause the connector to become damaged.
Is manual intervention required when adding or removing channels?
Automatic adjustment of the optical amplifiers when channels are added or removed achieves optimal system performance. This is important because if there is just one channel on the system with high power, degradation in performance through self-phase modulation can occur. On the other hand, too little power results in not enough gain from the amplifier.
Does the system use fluoride- or silica-based fiber amplifiers?
In the 1530- to 1565-nm range, silica-based optical amplifiers with filters and fluoride-based optical amplifiers perform equally well. However, fluoride-based optical amplifiers are intrinsically more costly to implement. The long-term reliability of fluoride-based fibers has not yet been verified.
Can the system's number of wavelengths and bit rate be upgraded?
While the answer is yes for all DWDM systems, planning for this is critical. If service providers put together their networks in a specific way and then want to upgrade, one of two things must happen: They need either more power or additional signal-to-noise margin. For example, each time providers double the number of channels or the bit rate, 3 dB of additional signal-to-noise margin is needed.
Does the system offer standards-compliant maintenance interfaces?
Standard transaction language 1 interfaces are widely available for DWDM systems. Interfaces should readily fit into a service provider's typical maintenance scheme.
