Fiber-in-the-loop (FITL) telecommunications systems use hundreds and thousands of optical network units (ONUs) to connect existing copper wire or twisted pair connections in homes and other user sites to the telephony network. Installation and maintenance of FITL systems typically require field technician on-site visits or service calls for functions such as adding second or additional lines, replacing failed line circuits, and cutting over new installations at each ONU. Field technician or craft service calls are generally labor intensive and expensive, and equipment handling by even the highest skilled field technicians can shorten the life expectancy of telecommunications equipment. Consequently, there is a need for alternative methods to perform the above-described operations.
The ONUs of an FITL system often are installed in hard-to-reach spots such as on poles, in hand holes, on cable strands, in muddy development sites, etc. They are sealed, and breaking their seal for routine functions will tend to reduce their reliability, introduce moisture and dirt, and require field technician time to reseal and re-verify the seal. Current system designs contemplate that ONUs will be deployed in great numbers (e.g., approximately 1 for every 8 homes or sites) compared with the higher numbers of sites that conventional communications remote terminals service. A failed circuit may require an immediate response to replace a line unit. This replacement or repair often occurs during off hours when labor rates are highest. If a field technician must go to each one of these sites to install connections, add second lines, or replace failed line circuits, system operating costs for FITL systems are likely to be substantially higher than similar costs for conventional systems. If a method and system existed that could save operating costs by allowing work to be scheduled during normal working hours, then such a method and system would be of great value to those companies responsible for maintaining and installing FITL telecommunications systems.
Another issue that FITL systems must address is system reliability. There is a need for a way to prevent having to break the ONU seals for the functions of installing connections, adding second lines, and replacing failed line circuits. A system meeting this need would eliminate line circuit failures from the reliability calculations as well as considerations for moisture and dirt that may enter an ONU as well as the requirement to reseal or re-verify seals for ONUs. As a result, FITL systems could more easily and simply meet design operating or reliability requirements and objectives.
It is an object of the present invention, therefore, to provide an ONU connection circuit that has technically advantageous hardware features to help extend the life and reliability of communication paths between a central office and a user site through the FITL system. The present invention accordingly avoids the need to open the ONU because the connections between the ONU line circuits and the user sites are remotely controlled. This improves the reliability of the telecommunications path, limits the amount of dust and moisture that may enter the ONU, and maintains the ONU seal. Without the need to re-verify the seal or to be concerned about dust and moisture entering the ONU, the present invention improves the reliability calculation for FITL systems.
Another object of the present invention is to provide a method and system for connecting an ONU with a plurality of user sites that include the steps of and circuitry for connecting a cross-connect matrix to a plurality of ONU line circuits. The method and system connect a plurality of drop connectors between the cross-connect matrix and a plurality of user sites or homes. The cross-connect matrix is remotely controllable to connect selected ones of the line circuits to selected ones of the drop connectors. This will connect the ONU with the plurality of user sites. As such, the method and system for connecting the ONU with the user sites can remotely add second lines, cutover new installations, and automatically bypass failed connectors more efficiently and economically than conventional methods of performing these functions.
An additional object is to take advantage of existing subsystems already present in a FITL ONU, including power, operations, communications, processor-based control, and environmental protection (both electrical and physical). These elements can be used by the present invention at no incremental cost--a significant advantage over a separate stand-alone metallic cross-connect.
Yet another objective of the present invention is to advantageously use the electronic circuitry associated with the ONU to immediately respond to line circuit testing that reports a failed line. Using the present invention, it is possible to automatically switch out a failed line upon electronic indication of its failure. This can eliminate a user having to report the FITL failed line and can improve overall FITL system operation, reliability, and user satisfaction.
It is yet a further object of the present invention to improve the management of connections between ONUs and user sites. Because the present invention provides remote control of user site-to-ONU connections, field technicians service trips can be minimized. Thus, hot cutover connections, and line circuit repair functions can occur in a well-managed way during regular normal working hours.
As yet a further object, the present invention provides an anti-sabotage feature for the optical network units. When service is to be denied on individual drops served by electronic line circuits, it is common practice to simply deactivate these circuits. Protection against malicious overvoltage from the deactivated drops requires physically disconnecting them, a labor intensive step, particularly in the case of FITL ONUs. The present invention automatically creates an open circuit between the user site and the ONU, so a would-be saboteur cannot induce from a user site an over-current condition in the communication connection to the ONU. Such an over-current condition could seriously damage electronic circuitry associated with the telecommunications line. This is a material distinction between the present invention and conventional systems.