Claudio Floridia

Fiber Optic Bending Sensor for Water Level Monitoring: Development and Field Test: A Review

In this paper, we describe a low cost optical sensor of water level based on fiber bending effect associated to the use of an elastomeric membrane. The sensor proposed has a particular design to be simple, reliable, and low cost. It is suitable to be used in tubes of embankment dams, tanks, and reservoirs. The sensor uses a standard single mode fiber and can measure the water levels up to 10 m or more, choosing the appropriate membrane. This paper describes the development of the sensor, a theoretical modeling, and the results of laboratory and field tests. Seven sensors were installed in an embankment dam where they have been used in a real time monitoring system based in optical time domain reflectometry.

WDM transmission of 3×1.12-Tb/s PDM-16QAM superchannels with 6.5-b/s/Hz in a 162.5-GHz flexible-grid using only optical spectral shaping

We demonstrated the transmission of 3×1.12-Tb/s superchannels (5×224-Gb/s PDM-16QAM) in 162.5-GHz flexible-grid, 6.5-b/s/Hz SE, using only optical spectral shaping, over SSMF-EDFA link. A maximum reach of 600-km with 3-ROADM passes was obtained employing nonlinear compensation.

Theoretical and experimental comparison between power and degree of polarization based optical fiber current sensors

This paper presents a theoretical and experimental comparison of two techniques of optical fiber current sensors (OFCS) based on the Faraday Effect: the power and the degree of polarization (DOP) methods. The DOP method is shown to be insensitive to state of polarization (SOP) changes induced by environmental conditions. A maximum variation of 0.4% in the DOP value in the entire range of applied current from 0 to 100 A was measured. It is the first time to our knowledge that this fact was experimentally verified. Also, for the first time known it is reported that zero current response, DOP = 0.996, is in agreement with the theoretical expected value of unitary DOP. Besides, the theoretical and experimental normalized DOP is shown to have a maximum difference of 0.33% in the entire range of applied current. On the other hand, the power method OFCS is greatly affected by SOP changes. In order to be used in a practical application, its complexity must be increased by the use, for example, of polarization maintaining fibers instead of standard fibers used in the DOP method, increasing the cost of the sensor element.

Comparative analysis of Fiber Grating versus Fiber Powering for fiber optical sensing applications

We present a comparative analysis between Fiber Grating versus Fiber Powering for fiber optical sensing applications. Both technologies were compared generically and experimentally by means of one temperature sensing experiment.

On-field distributed first-order PMD measurement based on pOTDR and optical pulse width sweep.

A method for PMD distributed localization and estimation based on polarization optical time domain reflectometer technique, pOTDR and pulse width sweep is used on-field for the first time. The method consists in launching light pulses with variable widths in an optical fiber under test and then analyzes the Rayleigh backscattered signal spatial power distribution after passing through a polarizer. Both localization and PMD magnitude are function of OTDR pulse width and can be obtained from the ripple analysis, enabling the characterization of the fiber links.

Field and Laboratory Demonstration of a Fiber-Optic/RF Partial Discharges Monitoring System for Hydrogenerators Applications

In this paper, we present the results of a hybrid fiber-optic and RF-sensing technology for monitoring partial discharges on hydrogenerators, which can also be used for several other applications. The main advantages of the proposed system are passivity, flexibility, nonintrusive, inherently dielectric, and human and equipment risk-free. We describe the performance evaluation of the sensing system in laboratory and in field trial installed in a hydroelectric power station located in north of Brazil.

Fiber optic interferometric method for acoustic emissions detection on power transformer's bushing

Fiber optic interferometric method for acoustic emission (AE) detection in power transformers bushing is developed and tested in emulated AE signals. It was shown that the proposed system can detect AE from inside a bushing replica. It was also shown that system sensibility is better than traditional piezoelectric acoustic sensors usually used for AE detection originated from partial discharge (PD) on power transformers.

Temperature sensing in high voltage transmission lines using fiber Bragg grating and free-space-optics

In this work we proposed the use of free-space-optics (FSO) to transmit and receive the optical signals from optical fiber placed in ground potential to the FBG fiber optics at high voltage potential, using a pair of optical collimators. The technique evaluation was performed in a prototype for the study of sensitivity to optical alignment and in an external environment using emulated sensing systems for both bus bar and overhead transmission line with real isolator chain. It has been shown that the FSO system allows collimators operate at distances of 500 mm to 2.000 mm. This range of distances is similar to the length of insulator’s chain up to 230 kV. It was also shown that the proposed system can be used in real external environment for bus bar temperature monitoring in substations, where, even if the time out of the system is of 45%, with major interruption time of almost 15 hours, the majority of the interruption time was less than 18 minutes long. On the other hand, system has to be improved in order to be used in overhead transmission line. As tested for a real isolator chain the system shown a time out of 80.3%, with significant number of events of interruption acquisition time greater than 150 minutes. It is believed that for overhead power lines, system must be installed in rigid surge arresters or in a line post where it is expected to have similar results as in substation bus bars monitoring.

Optical fiber sensor for pressure measurement based on elastomeric membrane and macrobending loss

We propose a fiber optic sensor array based on bend loss assessed by optical time domain reflectometry (OTDR). The sensor mechanism is based on optical fiber bending loss compressed by external pressure. An elastomeric surface is applied to the sensor in order to communicate external pressure to the fiber coil and also, this make sensor able to deal with degradation coming from aggressive environments. The sensing system proposed is able to monitor liquid or gas pressure in different environments, such as water, oil, alcohols, some diluted acids and others, depending only of elastomeric membrane choice. In order to protect the sensor stage against environmental degradation a plastic packaging was chosen. Bend loss measurements is taken concerning the number of fiber loops involved in the sensor, pump signal wavelength and temporal width. This long for the best parameters in the sensor construction. The specific case of the sensor applied to water percolation monitoring from embankment damns is detailed in this paper; for this application the sensor array have a number of at least six stages totally independent each other, in such a way that each stage can be developed to monitor a specific environment. Sensors have shown good performance in field tests, reaching work range from 0.1 to 0.6 atm with 0.05 atm of precision.

A Simple Method to Localize and Estimate PMD in Optical Fibers using the Polarization Optical Time Domain Reflectometry Technique

We propose and demonstrate experimentally a method for PMD localization and estimation based in the analysis of the ripple of polarization optical time reflectometry trace as a function of temporal pulse width launched signal.