Creating a cost-effective plug-and-play FTTP architecture
By Randy Reagan, ADC -- The plug-and-play approach to an FTTx infrastructure--made possible by factory-connectorized MSTs and drop cables terminated with hardened connectors and adapters--results in significant cost savings compared with traditional spliced architectures.
The plug-and-play approach to an FTTx infrastructure--made possible by factory-connectorized MSTs and drop cables terminated with hardened connectors and adapters--results in significant cost savings compared with traditional spliced architectures.
By Randy Reagan, ADC
Today's fiber-to-the-premise (FTTP) network planners must build flexible and reliable architectures at the lowest possible cost. New hardened connector technologies, coupled with multi-port service terminals (MSTs), are enabling accelerated plug-and-play deployment while ensuring a long life with reduced long-term operational expenditures.
Plug-and-play architectures create more technician-friendly systems by reducing the need for highly skilled technicians to perform installation tasks, such as splices and drop cable connections. By reducing the number of splices in the distribution network, installation and maintenance is faster and easier. Moreover, easy access at the MST facilitates maintenance and troubleshooting, eliminating the need to send a splice technician to the home.
As with any FTTP solution, the unique circumstances of each deployment requires careful planning, and every aspect of the network build-out must be considered. But wherever the situation warrants, a plug-and-play architecture can be a very cost effective means to quickly and easily deliver the benefits of fiber to meet ever-increasing bandwidth demand. Reducing the number of splices, splice technicians, and splice crews required to turn up customer service reduces both installation and operational costs.
Hardened connectors are key
Without the huge strides made in hardened connector technology in recent years, a reliable and efficient plug-and-play FTTX architecture would not be possible. Hardened connectors are specifically designed and tested for use in outside plant (OSP) applications. Higher performance standards and manufacturing improvements have resulted in lower insertion and return loss.
Hardened fiber-optic connectors that withstand the rigors of harsh OSP environments provide the same reliability and performance of spliced networks--with the added benefits of lower installation costs, greater flexibility, and easier access. Rugged connector systems consist of connectors and adapters that are hardened to protect against the most severe conditions, including extreme temperature, moisture, ultra-violet (UV) radiation, chemical exposure, and other harsh OSP conditions.
Hardened connectors are watertight and can be installed on the external surface of an enclosure, providing easy access points in above- or below-ground installations. Each connector undergoes a full suite of tests designed to ensure high performance and reliability in OSP applications.
The full qualification program for these connectors subjects them to the same real-world conditions likely to be found during their network service life. Each connector must meet Telcordia standards, such as GR-326, GR-771 and GR3120, designed to test for robust and reliable environmental performance. A battery of tests are conducted that expose the rugged connector to thermal aging, thermal cycling, humidity aging, humidity condensation cycling, and post thermal cycling.
The hardened connector also must undergo vibration testing and a full range of mechanical stress tests, including flex, torsion, proof, and transmission with applied load. Additional test requirements include impact and crush resistance to simulate normal incidental forces, as well as water submersion and freeze-thaw testing. A variety of optical monitoring tests verify the ability of the connectors to maintain the required insertion loss and reflection performance during and after extreme exposure to harsh testing environments.
Finally, in addition to service life testing, a full regiment of reliability tests is necessary to certify the longevity of the hardened connector system. Products are tested for extended time periods while subjected to specific harsh conditions. The result is a hardened connector product that will withstand exposure to any outside plant environment.
The plug-and-play solution
Hardened adapters are mounted on enclosures at the street outside the residence and at the optical network terminal (ONT) on the side of the residence. A hardened drop cable is used to connect between the enclosure and the ONT.
The drop cable is a factory-connectorized assembly with hardened connectors on each end. These cables also have been pre-tested and certified at the factory to meet performance requirements. Each hardened connector and adapter is protected by a protective cap or plug until it is put into service.
When connected, the protective caps and plugs are removed to enable the inner connector components to be aligned to complete the connection. Once the connector is engaged with the adapter, it is sealed using a watertight O-ring seal. Factory-connectorized drop cables enable non-technical field installation of the network drop cables, eliminating the need for splicing or highly skilled technicians.
In addition, simplified cleaning techniques for the hardened connectors make it easy to maintain the network. To clean the connector and adapter, the dust caps and plugs are removed to expose the inner optical components. The adapter then is cleaned using a standard swab, and the connector is cleaned using lint-free wipes.
Finally, an arrow on the connector itself aligns with a notch on the adapter, thereby ensuring precise alignment of the connector into the optical port. Although simple in nature, this feature provides a vital method for ensuring high reliability and speed when mating a connector to a hardened adapter.
The multi-port service terminal
The other vital element to the cost-effective plug-and-play FTTx network architecture is the MST that typically resides between the fiber distribution hub (FDH) and the subscriber. The hardened MST enclosure is terminated and sealed in the factory with fiber cable stubs and hardened adapters on the exterior surface. These units are specifically designed for outside environments and installed in hand-holes or pedestals, mounted on utility poles or overhead cable, or simply secured to any convenient flat surface.
MSTs are connected to the network by splicing the stub cable to a main distribution cable. This splice is achieved without the need to access the enclosure. The versatile mounting schemes adapt to almost any installation technique, and the MSTs are designed to withstand direct exposure to extreme temperatures and humidity. They also are highly resistant to water penetration, chemicals, and corrosion.
Hardened connectors are used for the optical ports of the MST, and each port is sealed with a threaded dust cap to prevent dirt or moisture to enter. MSTs are available in two-, four-, six-, eight-, or 12-port configurations and accept drop cables that are terminated with hardened connectors. The factory-installed terminations of both the drop cables and the MSTs eliminate splicing and can be installed by less-skilled technicians, again saving installation costs and enabling rapid service turn-up.
The plug-and-play approach to an FTTx infrastructure--made possible by factory-connectorized MSTs and drop cables terminated with hardened connectors and adapters--results in significant cost savings compared with traditional spliced architectures. Despite the additional costs associated with adding more service terminals, the savings in fiber cable, cable placement, and splicing more than offset the added expense.
Randy Reagan is the program manager for FTTX Global Connectivity at ADC (Minneapolis, MN). He may be reached via the company's Web site at www.adc.com.