Network intelligence - optical networks of new generation

2008-08-25

Introducing new services is a chance to attract new subscribers and increase revenue coming from the network. On the other hand, it is also a great challenge. One of the key factors, influencing a success of the business, is the optimization of capital and operational expenditures and ensuring a given quality level together with simple operation of new services. A great influence on the service quality level and customer satisfaction have the decisions taken up during the whole life of the network – starting with the design phase where the network architecture is defined, through the choice of equipment providers, integrators (direct influence on deployment efficiency), ending with network operation when it gives revenues.

These needs require high level of equipment functionality and intelligence. An excellent example of such equipment is a new VECTOR product series, including the BETA PRO 60, optical node based on digital technology.

The architectures of the state-of-the-art cable networks based on fiber optics can vary significantly. On the one end we can have a traditional HFC (Hybrid Fiber Coaxial) networks, on the other end more popular Fiber Deep networks or the most advanced FTTH (Fiber to The Home) networks where a fiber ends at the subscriber’s home.

Traditional optical nodes used in HFC networks cannot be implemented in Fiber Deep networks due to other technical and economical requirements. For such modern networks an optical fiber is usually the last active element in the network. As a consequence, it is a key system element influencing capital and operational expenditures as well as quality. In order to obtain optimal capital expenditures for deployment of the Fiber Deep network one should pay special attention to optical fibers chosen for the network.

The BETA PRO 60 optical fiber is an excellent example of the device fulfilling all requirements of the Fiber Deep architecture. It is a very modern device with many network configuration options. The node has two active paths. One of them has the possibility of passive signal splitting. This is why the node has three RF outputs. The unit allows to install 1 or 2 optical receivers for redundant network configuration in the downlink path. 1 or 2 optical transmitters can be installed in the return path. It makes the redundant configuration or segmentation of the return path possible. The BETA PRO 60 node is a continuation of the digitally controlled node family which is very popular among the network operators. The unit has a built-in microprocessor which controls attenuation and equalization in regulation points, ingress switches and configuration/operation of the AGC circuit. All values can be entered via the keyboard and can be observed at the LED display. Redundancy/segmentation/combining of the return path is also controlled by the microprocessor. Thus, there is no need for additional plug-in modules to configure these modes of operation. The electronic control makes the traditional plug-in modules useless and reduces the operational costs. Digital control solves problems connected with mechanical connections and failures typical for traditional plug-ins. The module cannot be installed improperly, which reduces failures during module installation. It is especially important when the unit is installed in a place with limited access by a technician. Digital control reduces problems caused by element aging and changing parameters of mechanical connections. It increases the unit durability against moisture, dust, etc. It is also possible to pre-configure the unit before installation.

Another advantage of the microprocessor control is the ability of the input optical power level measurement without any additional meters and the need of disconnecting the fiber connectors. One can measure the level choosing the proper menu option and reading the value on the internal display.

There is one more advantage over a traditional unit with plug-in modules. The services are not interrupted during unit maintenance and adjustment. It is an especially important feature for VoIP or VoD services and Internet access.
The BETA PRO 60 node has a high gain ensuring a high output signal level. AGC keeps the output signal at the same level within a wide range of the input optical signal. The range of the optical input power levels depends on the type of the optical receiver. There are two types:

• Low Gain for standard HFC applications: -3 dBm...+2 dBm
• High Gain for Fiber Deep applications: -7...-2 dBm.

Such a solution allows usage of the node in standard HFC applications and easy reconfiguration for Fiber Deep applications in the future by replacing the optical receiver. As the amplification circuit the BETA PRO 60 node uses Power Doubler IC’s which have a high output level with a low intermodulation distortion level. Thus, it is possible to distribute signals directly to a big number of subscribers without additional intermediate amplifiers. The novelty design with microprocessor control and AGC helps to improve the stability of signals in the network and, as a consequence, its quality. The additional advantage is the improved network reliability and easier installation and maintenance without traditional adjustment. As an option, a transponder (HMS or DOCSIS/EuroDOCSIS) can be installed in the node. It allows remote control and management of the node. Together with the microprocessor control it gives a wide possibility of control and management of field units from NOC (Network Operation Center). DOCSIS/EuroDOCSIS transponders have a WWW page for remote control and management via a Web browser without additional software. All the mentioned features give substantial cost reduction during network deployment and operation for both fiber and coaxial parts and offer very good parameters (quality and reliability) of the offered services.

The BETA PRO 60 optical node is a modern device with many advantages like uninterrupted operation during adjustment and configuration due to microprocessor control or simplified maintenance. Additionally, AGC ensures a stable network operation while the modern design solutions offer optimal noise and intermodulation parameters which reduce the number of active elements in the network without reduction of high signal levels.