A research group including members from Tokyo Institute of Technology (Tokyo Tech) and Japan Society for the Promotion of Science have developed a real-time fiber-optic distributed sensing system for strain and temperature. The system requires light injection from only one end of the fiber and can achieve a sampling rate of 100 kHz, an improvement of over 5,000 times the conventional rate.
Aging degradation and seismic damage of civil infrastructure pose a serious problem for society. One promising technology for monitoring the condition of structures is optical fiber sensing. By embedding long optical fibers into a structure, strain and temperature distributions along the fibers can be detected. Among the various types of optical fiber sensors, distributed strain and temperature sensors based on Brillouin scattering have received much attention due to their high sensitivity and stability. In particular, Brillouin optical correlation-domain reflectometry (BOCDR), which operates based on the correlation control of continuous lightwaves, is known to be an intrinsically one-end-access distributed sensing technique with high spatial resolution (< 1 cm). However, the highest sampling rate reported for BOCDR was 19 Hz, resulting in a relatively long total time of distributed measurement (from several tens of seconds to several minutes). Seeking to resolve this shortcoming, researchers Yosuke Mizuno and Kentaro Nakamura from Tokyo Tech, Neisei Hayashi, a Japan Society for the Promotion of Science fellow from the University of Tokyo, and their collaborators recently succeeded in increasing the sampling rate of BOCDR to 100 kHz, over 5,000 times the previous rate, enabling real-time distributed measurement. Their study is published in the December 2016 issue of Light: Science & Applications.
In all Brillouin sensors, the strain and temperature dependence of the Brillouin frequency shift (BFS) is exploited to derive strain and temperature. In conventional BOCDR, the BFS is obtained by performing a frequency sweep over the whole Brillouin gain spectrum (BGS) using an electrical spectrum analyzer. Thus, the sweep speed of the spectrum analyzer limits the sampling rate to 19 Hz. By instead sweeping the frequency spectrum using a voltage-controlled oscillator, the researchers were able to achieve a higher-speed acquisition (Fig. 1(a)). However, deriving the BFS from the BGS still limited the sampling rate. To speed up the system further, the BGS was converted into a synchronous sinusoidal waveform using a band-pass filter, allowing the BFS to be expressed as its phase delay. Then, using an exclusive-OR logic gate and a low-pass filter, the phase delay was subsequently converted into a voltage, which was directly measured (Fig. 1(b)).
A strain sampling rate of up to 100 kHz was experimentally verified by detecting a 1-kHz dynamic strain applied at an arbitrary position along the fiber. When distributed measurements were performed at 100 points with 10 times averaging, a repetition rate of 100 Hz was verified by tracking a mechanical wave propagating along the fiber (Fig. 2). Thus, the researchers were the first to achieve one-end-access real-time distributed Brillouin sensing. A video demonstration of the system is available online (Single-end-access real-time distributed strain sensing – YouTube).
The sensing system is anticipated to be of benefit in monitoring the health of various structures, ranging from buildings and bridges to windmill blades and aircraft wings. The system also has potential applications in robotics, acting as electronic “nerves” for detecting touch, distortion, and temperature change.
Realizing Compact, Low-Cost, High-Speed Radio Communication Systems for the IoT Age
In collaboration with the National Institute of Information and Communications Technology (NICT), Associate Professor Hiroyuki Ito and Professor Kazuya Masu, et al., of the Tokyo Institute of Technology, developed a new algorithm and circuit technology allowing high-frequency piezoelectric resonators to be used for phase locked loops (PLL). It was confirmed that these operate with low noise and have an excellent Figure of Merit (FoM) compared to conventional PLLs.
This technology allows high-frequency piezoelectric resonators to be used in place of crystal oscillators which was a problem for realizing compact and low-cost radio modules. This greatly contributes to the creation of compact, low-cost, high-speed radio communication systems for the IoT age. High-frequency piezoelectric resonators are compact, can be integrated, have an excellent Q value, and oscillators that use these have excellent jitter performance. High-frequency piezoelectric resonators had greater issues with resonance frequency variance and temperature dependability compared to crystal resonators. However, these issues were resolved by the development of a PLL that uses a channel adjustment technique, which is a new algorithm.
A prototype was fabricated by a silicon CMOS process with a minimum line width of 65 nm, and a maximum frequency output of approximately 9 GHz was achieved with a phase fluctuation of only 180 femtoseconds. Power consumption was 12.7 mW. This performance is equivalent to a PLL Figure of Merit (FoM) of -244 dB, and it has the world’s top-class performance as a fractional-N PLL. This can contribute to the realization of compact, low-cost, high-speed radio communication systems.
Building extremely small electronic components and circuits made from individual molecules requires manipulation of the molecules into the desired arrangement. However, this remains difficult because of inconsistency in sites where molecules attach within nano-sized “circuit boards” and in the properties they exhibit in such circuits. Various research teams have sought to overcome this by studying single molecules positioned in a tiny gap between two electrodes, but obstacles to characterizing their positional and electrical features have surfaced.
A research team centered at Tokyo Tech has now precisely characterized the type of binding of a single molecule between two gold electrodes. The researchers measured the current flow when this single molecule bridged the gap between the electrodes and completed an electrical circuit, as well as the measuring the Roman scattering. Their measurements revealed the exact sites at which each end of this molecule connected with the tips of the gold electrodes, and indicated that the molecule preferentially took on three different arrangements (or bindings). This breakthrough should help to ensure site-specific binding of individual molecules used as components in nano-sized electronic circuits, making such circuits more reliable.
Recently reported in the Journal of the American Chemical Society (” Site-Selection in Single-Molecule Junction for Highly Reproducible Molecular Electronics”), this novel approach using two different analytical procedures was applied to clarify exactly how a single molecule of benzenedithiol bridged a gap of two-billionths of a meter between two gold electrodes and completed an electrical circuit. These two procedures involved measuring the current and voltage through the circuit while simultaneously analyzing the Raman scattering from a laser focused on the electrode gap. Data from over 200 of these so-called “single-molecule junctions” showed that three benzenedithiol configurations dominated, in terms of how they attached to the electrode tips, and it was possible to distinguish between them using these procedures. This novel approach can thus reveal the exact configuration of a single molecule, which enables precise construction of molecular-based circuits.
Tokyo Institute of Technology (東京工業大学 Tōkyō Kōgyō Daigaku?, informally Tokyo Tech, Tokodai or TIT) is a national top-tier research university located in Greater Tokyo Area, Japan.
Tokyo Tech is the largest institution for higher education in Japan dedicated to science and technology. Tokyo Tech enrolled 4,850 undergraduates and 5,006 graduate students for 2009–2010. It employs around 1,400 faculty members.
Tokyo Tech’s main campus is located at Ōokayama on the boundary of Meguro and Ota, with its main entrance facing the Ōokayama Station. Other campuses are located in Nagatsuta and Tamachi. Tokyo Tech is organised into 6 schools, within which there are over 40 departments and research centres.
Operating the world-class supercomputer Tsubame 2.0, and taking a breakthrough in high-temperature superconductivity, Tokyo Tech is a major centre for supercomputing technology and condensed matter research in the world.
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Robot unfolds from ingestible capsule, removes button battery stuck to wall of simulated stomach.
In experiments involving a simulation of the human esophagus and stomach, researchers at MIT, the University of Sheffield, and the Tokyo Institute of Technology have demonstrated a tiny origami robot that can unfold itself from a swallowed capsule and, steered by external magnetic fields, crawl across the stomach wall to remove a swallowed button battery or patch a wound.
The new work, which the researchers are presenting this week at the International Conference on Robotics and Automation, builds on a long sequence of papers on origami robots from the research group of Daniela Rus, the Andrew and Erna Viterbi Professor in MIT’s Department of Electrical Engineering and Computer Science.
“It’s really exciting to see our small origami robots doing something with potential important applications to health care,” says Rus, who also directs MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL). “For applications inside the body, we need a small, controllable, untethered robot system. It’s really difficult to control and place a robot inside the body if the robot is attached to a tether.”