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TDR and OTDR Systems
TDR and OTDR systems can be either manual or remote read.
Manual systems have both advantages and drawbacks. These are:
- They are considerably cheaper than the remote systems in that the cost of coaxial or light switches, enclosures, batteries and charging systems, transmission systems, and enclosures are avoided. As most systems allow digital recording of the trace data, traces can be quickly and easily analyzed upon return to the office;
- New cables can be quickly appended to the system as no trunks or leads are required to the borehole collar;
- Someone must be delegated the task of consistently and accurately recording trace data for each monitoring point. In addition, it must be insured that the data is, in fact analyzed, and not merely collected, and;
- The advantage of real time, continuous monitoring available with TDR/OTDR is lost with a manual system. Automated warning systems cannot be utilized.
Remote systems have their advantages and shortcomings as well:
- They are more expensive, as a host of support hardware is required.
- Tthe central station, or stations, must be optimally located for the automated monitoring system(s). Trunk lines are necessary to collect individual monitoring leads.
- Personnel requirements are reduced somewhat, although someone must maintain the cable network. Data analysis is still required, as checks must be conducted on the machine analyses.
- Real time, continuous monitoring is available. This allows alarms to be sounded, personnel to be alerted to check for actual or impending failure, digital map location of cable and fault location (GPS coordinate calculated) transmitted to responding personnel.
Some considerations regarding system layout for both OTDR and TDR systems are given as attached PDF files.
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