AFORS autonomous fibre-optic rotational seismograph: Design and application

Fibre-Optic Sagnac Interferometer as Seismograph for Direct Monitoring of Rotational Events

“…A detailed description of the AFORS system was published previously (Jaroszewicz at al., 2011a(Jaroszewicz at al., , 2011b) hence here we summarized the above data regarding its construction, calibration and management. Now we present two examples of these devices -AFORS-1 located in the Książ (Poland) seismological laboratory for the investigation of the rotational events connected to earthquakes, and AFORS-2 located in Warsaw (Poland) used for initial works connected to the investigation of the irregular engineering construction torsional response and the interstory drift (Jaroszewicz et al, 2011c).…”

“…1a, has been developped. The ASPU enables the detection of a rotation rate  from proper selection (special low-pass filters) and processing (in digital form) the first A 1 and the second A 2 amplitude of the harmonic output signal, on the basis of the following relation (Jaroszewicz et al, 2011a):…”

“…The evaluation of the optical and electronic constans needs a sensor calibration process, which is based on the measurement of the Earth rotation for Warsaw, Poland i.e.  E = 9.18 deg/h ≡ 4.4510 -5 rad/s Jaroszewicz et al, 2011a After the practical construction of the AFORS devices, their accuracy has been checked. However, this work made in MUT located in Warsaw city, could give limited information on the system accuracy because of urban noises.…”

“…Additionally, the top right corner of bookmarks for the given system on server contains the information on a current date and time and the four main AFORS's parts of state of work (good -as green, partially good as yellow or no work -as black, respectively). The bookmark GSM/GPS (not shown in figure, see for example Jaroszewicz et al, 2011a) monitors in real time the GSM parameters as well as the GPS parameters which include the AFORSes' global localization (see Fig. 5b).…”

The laboratory investigation of the innovative sensor for torsional effects in engineering structures’ monitoring

“…Such research can be treated as an area of interest of the strong motion seis− mology [2] according to the expected high amplitude of rota− tion -even up 10 rad/s. Construction of FOSREM based on authors' experiences regarding construction and investiga− tion [21] of previous systems designed for continuing moni− toring of rotational events connected with earthquakes [22,23], mainly AFORS (Autonomous Fibre−Optic Rota− tional Seismograph) installed in the seismological observa− tory in Książ, Poland. In comparison to AFORS, by changes in optical, as well as electronical part, FOSREM protects detection rotation rate with a higher amplitude (up to 10 rad/s compare to 10 -6 rad/s for AFORS); enables to measure a rotational component in a wide frequency band (from 0 Hz to 328.12 Hz), and is more portable devices which makes it work within the temperature range of 0-50°C.…”