Description
This activity will be dedicated to install a DAS system. Before installing the DAS, it is necessary to see the feasibility and preparation of the submarine cable to receive this equipment. First, the optical fiber will be verified in terms of its compatibility with the DAS operating system. This study will be performed using an OTDR to monitor losses, defects and connectors along the cable. The DAS system works mainly with unidirectional measurements and reflected signals. All the measurements will be performed in dark fibers. DAS features allow measurements up to 50 km, with spatial resolution of 10 m, equivalent to 5000 seismographs up to every 10 meters of fiber.
As for data acquisition, we will have a measurement time of one year with DAS. However, it is important to analyze the first month to optimize the software. In this case, in addition to the recorder in the local seismic activity (background), it will increase the probability of detecting the occurrence of high magnitude earthquakes and other seismic occurrences of a random/unpredictable nature.
Data will be stored in local external disks and collected at the end of the measurement period. Acoustic sampling should be adjusted to the expected signals to be measured (typically below frequencies of 250Hz) in order to avoid unnecessarily large file sizes. Therefore, the two acquisition settings will be: 365 days of measurement at low acoustic sampling (50-100Hz) that correspond ca. 80TB of data.
Within this task the following activities can be envisaged within this activity:
1- Preparation & Measurement feasibility
2- Data acquisition
3- Logistics & Timeframe
Expected results
Within this activity one expects to have a DAS system monitoring a cable submarine in Azores. The system will be optimized and remotely controlled by software due to difficult access by the team. Ensure acquisition settings for 365 days of measurement at low acoustic sampling. At the end of the recording period the complete set of raw data will be available at INESC-TEC and IPMA/IDL data storage facilities.