This paper presents the design, fabrication, and characterization of a novel all-optical fiber ultrasound imaging system based on the photoacoustic (PA) ultrasound generation principle and Fabry-Perot interferometer principle for biomedical imaging applications. This system consists of a fiber optic ultrasound generator and a Fabry–Perot (FP) fiber sensor receiver. A carbon black polydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasound generator. The black PDMS material was coated on the tip of a 1000 μm core size multimode fiber (MMF) to generate the ultrasound signal. Two layers of gold, PDMS and a single mode fiber (SMF) were used to build the FP fiber sensor receiver. The system verification test proves the ultrasound sensing capability. The biomedical imaging test validates the ultrasound imaging capability. There are many advantages of this all-optical fiber ultrasound imaging system, such as small size, light weight, ease of use, and immunity to electromagnetic interference. This research has revealed valuable knowledge for the further study of biomedical imaging in a limited space, e.g., catheter based intravascular imaging, tissue characterization, tissue identification and related biomedical applications.
In this paper, we present a novel fiber optic ultrasonic sensing system to conduct a 2D temperature field monitoring. The fiber optic ultrasonic sensing system was used as an ultrasonic pyrometer to measure the temperature field. The ultrasonic pyrometer was based on the thermal dependence of the speed of sound in air. The speed of a sound wave traveling in a medium was proportional to the medium’s temperature. A fiber optic ultrasonic generator and a microphone were used as the ultrasonic signal generator and receiver, respectively. A carbon blackPolydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasonic generator. A test was performed outside of a lab furnace, the testing area temperature range was from 26°C to 70°C. A 2D temperature field was mapped. The 2D temperature field map matched with the reference thermocouple results. This system could lead to the development of a new generation temperature sensor for temperature field monitoring in coalfired boilers or exhaust gas temperature monitoring for turbine engines.
This paper presents a characterization of ultrasonic generation from the sidewall of an optical fiber. Ultrasonic generation from an optical fiber could have broad applications, such as ultrasonic imaging, ultrasonic nondestructive test (NDT), and acoustic pyrometers and so on. There are many advantages of these fiber-optic ultrasonic transducers, such as small size, light weight, ease of use, and immunity to electromagnetic interference. This paper discusses two main factors that will influence the signal strength generated by the sidewall of the ultrasonic generator. The two factors are the thickness of the photoabsorption material and the optical energy emitted from the sidewall fiber. A 20 mm length fiber-optic sidewall ultrasonic generator was used for the characterization. Gold-nanocomposite materials were used as the photoabsorption material. A hydrophone was used to detect the ultrasonic signal. The ultrasonic time and frequency profile and the ultrasonic field distribution at the longitudinal section of this fiber-optic sidewall ultrasonic generator have been characterized in this paper.
This paper presents a novel fiber optic ultrasonic sensing system to measure high temperature in the air. Traveling velocity of sound in a medium is proportional to medium’s temperature. The fiber optic ultrasonic sensing system was applied to measure the change of sound velocity. A fiber optic ultrasonic generator and a Fabry-Perot fiber sensor were used as the signal generator and receiver, respectively. A carbon black- Polydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasonic generator. A water cooling system was applied to cool down the photoacoustic material. A test was performed at lab furnace environment (up to 700 ℃). The sensing system survived 700℃. It successfully detect the ultrasonic signal and got the temperature measurements. The test results agreed with the reference sensor data. The paper validated the high temperature measurement capability of the novel fiber optic ultrasonic sensing system. The fiber optic ultrasonic sensing system could have broad applications. One example is that it could serve as acoustic pyrometers for 3D temperature distribution reconstruction in an industrial combustion facility
Ultrasonic corrosion detection has been developed and widely applied in non-invasive tests in civil engineering. This paper demonstrates real time fiber optic ultrasonic corrosion detection on reinforcing rebar based on photoacoustic (PA) principle in non-invasive tests in civil engineering. The optical acoustic sensors are fabricated to monitoring the corrosion of rebar in concrete. This paper explores an approach to make an assessment for the level of rebar corrosion as well. From the experimental results, the trend of central frequency had a shift to lower based on the development of corrosion. Since the sensor can measure the rebar corrosion timely, it will have a significant step on structural health monitoring.