Fibre-Optic Sagnac Interferometer in a FOG Minimum Configuration as Instrumental Challenge for Rotational Seismology

The Fiber-Optic Rotational Seismograph—Laboratory Tests and Field Application

“…Regarding the description in Ref. [13], DTU enables a synchronous data recording from sensors with collecting information on a local disc, as well as transferring it to PCU via fiber link. PCU enables future data transmission using the internet or GSM/GPS to WEB FOSREM with a rate of up to 100 Mbps, as well as the power supply of sensors and DTU.…”

“…Physically each sensor can be divided into two basic parts: optical and electronic. The optical part, according to the schema in Figure 2, assures the Sagnac effect reversibility [17] and is constructed according to the description presented in our previous papers [11,13,15,19]. Only a substitution of a fiber coupler in loop and a piezoceramic phase modulator by a multifunction integrated optic chip (MIOC) (Idealphotonics Ltd., Shanghai, China) have been applied.…”

“…However, applications of the above rotational sensors are generally used separately, and for this reason, the reliability of the recorded data can be controversial. The comparison of results obtained by different devices concerning the same rotational events can be found in limited papers, for instance [5,11,12,13]. In order to gather reliable data, the idea of application of at least two systems designed according to the same technology, like for instance, in the well-known paper [14], is interesting and applied in this paper.…”

The Fiber-Optic Rotational Seismograph – Laboratory Tests and Field Application

“…Physically each sensor can be divided into two basic parts: optical and electronic. The optical part according to the schema in Figure 1 Calculation of the detected rotation is based on the following equation [17]:…”

“…where: A1A2is the first and second amplitude of the harmonic output signal u(t), Se -the electrical constant related with parameters of applied components. Above calculation is realized by the sensor's electronic part which realizes synchronous detection in a digital form with a special procedure of selecting and amplification of the first and second amplitude of harmonic output signal due to a large difference (4-5 orders of magnitude) of their amplitudes [17]. As one can see in Figure 2, the hardware of this part contains digital units with sophisticated software for system control and real-time data computation.…”