Optical Networking

An optical network is a network where the user-network interface (UNI) is optical and the data does not undergo optical-to-electrical conversion within the network (Fig.2). Note that only the data remains optical end-to-end; signalling, provisioning, and network management services may be implemented in the ON or over a separate network utilizing the fiber infrastructure.

 

Figure 2 - Service layer taxonomy

The users/clients of the optical network (ON) could be

• electronic switching equipment, such as

• SONET/SDH cross-connects,
• ATM switches,
• IP routers (recall Fig.1); or

• end-user equipment such as

• workstations,
• video servers, and
• so on.

In either of these cases, the ON user requires an electrical digital circuit, packet, or cell service. There are also situations where analog transport services may be preferred (e.g., video distribution in access networks).

The optical network adapter (ONA) is the interface between the optical network and the ON user. ONAs connect to the optical network at the UNI and use optical services (described below) to provide transport services to the ON users. ONAs may be standalone, connecting to one or more ON users through standard communication protocols, or integrated within a single ON-user device. The complexity and cost of an ONA depends strongly on the available optical services and the desired transport services. Note that in some situations, the ONA may contain sophisticated optical technology, such as optical memory, and therefore the UNI is not necessarily located where the optical signal is converted to electronics.