Researchers from India have presented a new development. Thanks to it the scientists can find toxic mercury in drinking water. The whole system is based on FBG sensors.
Fiber Bragg grating (FBG) sensors are utilized widely in industrial and commercial applications with the addition of fiber optic solutions. FBGS sensors are especially effective in stabilizing the wavelength of semiconductor lasers and are useful in extracting a single wavelength from the fiber. Fiber Bragg grating sensors are popular in different spheres, including aerospace, robotics, the oil and gas industry, etc. Achievements in creating fiber optic sensors and their applications make the Fiber Bragg grating sensors appropriate for other spheres and developments.
That’s why scientists from India decided to apply Fiber Bragg grating sensors to the mercury detecting system. We can find mercury particles everywhere in the environment. They can be produced not only by human-made causes, like industrial wastes but also by natural ones, for example, combustion of fossil fuels and volcanic eruptions. That’s why the creation of the mercury detection system with the help of FBG sensors was a very important step.
According to medical studies, mercury particles can easily enter the human body. The most common ways are water bodies and marine life. In the human gut, some microorganisms can turn mercury into organic and alkyl forms. These forms of mercury in the human blood-vascular system can lead to diseases of kidneys, nerves, endocrine, and other systems. So the mercury detection system based on fiber Bragg grating sensors plays a crucial role in health care activities.
The developed by the research team FBG sensors are portable in comparison with other traditional techniques. These techniques are gas chromatography and liquid chromatography methods were tested by time. They are considered to be precise and complicated. And they are not portable like fiber Bragg grating sensors. Moreover, they need much time and get more expenses because are made in special laboratories by professionals.
Scientists think that fiber Bragg grating sensors are an ideal decision for the developing mercury detection system. Fiber Bragg grating principles help to make this system cost-expensive and highly effective in comparison with the others. However, they agree that there is still a lot of work to do and Fiber Bragg grating sensors can be updated in the future.
Scientists from the USA have created a laser light-powered micron optics accelerometer. It is a micron sensor that locates any speed changes. The advantage of it is the fact that it functions over a greater range of frequencies and at a higher rate of precision than usual instruments.
The thing is that all micron optics accelerometers fix changes in speed by monitoring proof mass, or its position while moving, toward an unmoving reference point inside the HBG accelerometer. Herewith, the distance itself alters only if the micron optics accelerometer changes speed or direction.
The scientists created a design with supporting beams. The beams play the role of a harmonic oscillator or a spring that vibrated a single frequency. The FBG accelerometer comprises two chips and the laser light that goes through the bottom chip and emits at the top. A proof mass is installed at the top chip by silicon flexible beams. That allows a proof mass to move freely in response to acceleration. There is also a mirrored surface on the proof mass and a mirror fixed the bottom chip. That design forms an optical cavity.
While motion, the proof mass creates a signal that a micron optics accelerometer can adopt. The scientists used laser light to measure the alterations in distance between two reflective surfaces and watch any changes in the resonant wavelength. The proof mass could move freely and it supported one of the mirrored surfaces. The other surface including a microfabricated concave mirror was the fixed reference point.
That construction of the FBG accelerometer helped the scientists measure the cavity light with a high degree of precision. The proof mass moves when the device has an acceleration. Herewith, the length of the cavity alters as well as the resonant wavelength shifts. All this impacts the intensity of the reflected light.
While the process of the research, the micron optics accelerometer enabled the team to reach minimal measurement uncertainty acceleration frequencies spanning. According to the scientists, the device employs light as an activator and does not need periodic calibrations. Furthermore, the FBG accelerometer could detect any displacements of the proof mass.
The research team announced that further improvements in the micron optics accelerometer allow us to use it as a highly effective and portable device for the calibration of other accelerometers.
The topic of a smart city and how it should be implemented is one of the most discussed today. The problem is everyone understands something different by this term. However, all people agree on one thing — the advent of the era of “smart cities” is inevitable and fiber optic solutions play a crucial role in it.
First of all, the smart city is a modern urban management system, convenient transport, efficient fiber optic solutions, developed internal procedures of the urban environment. They also include modern channels of interaction with residents, infrastructure, big data, etc.
Additionally, the smart city is a big amount of data that is structured, accessible, and properly secured. When these factors are combined and managed, then the smart city will appear.
Components of smart cities
The elements of the smart city, in general, contain smart energy, a resource supply system, smart transport and security system provided by fiber sensors, a system of social services, and urban management. Only when all these parameters come together, this is a full-fledged smart city, not its elements.
In the smart city concept, the conventional infrastructure of housing and utilities is equipped with modern fiber optic sensors. Herewith, controllers and video cameras, connected to broadband networks and integrated with a platform for data collection and processing are installed too. All this data is analyzed and allows achieving great efficiency and optimization of city services and local businesses, whether it is the expenditure of resources or the management of passenger traffic.
In theory, everything looks simple, but in reality, there are a lot of obstacles. Those who develop the ideology of a smart city have to face a lot of barriers, both typical for large IT projects and individual ones. This fact seriously complicates the process. Cities must meet one common requirement to become smart: to collect reliable information (from fiber optic sensors). Based on data it is possible to develop fiber optic solutions for the long term because data is crucial in our time. If you integrate fiber sensors into the city’s infrastructure and create new data collection points — including from citizens with their mobile devices — the smart city administration will be able to analyze big data to more accurately track and predict what is happening. This is also evident in the deployment of communication systems: local fiber optic networks, municipal Wi-Fi, specialized applications for specific tasks (smart parking, street lighting, waste disposal, and recycling).
As already mentioned, the concept of a smart/safe city includes components from a wide variety of areas of life. Moreover, the consumers of these elements are both business and government organizations, as well as the residents of cities themselves.
Fiber sensors as a component of smart transport
In large cities, we are used to applying intelligent traffic analysis and route planning services. These services are based on fiber optic solutions for the collection and processing of data on vehicle movement. Nevertheless, the concept of smart transport is much broader.
Equipping vehicles with location and speed fiber sensors, as well as video cameras, allows solving a variety of tasks. For example, they provide security to logistics management. Fiber optic sensors allow detecting where the car is, what it does and how it can plan its further route.
The development of smart transport will lead to the emergence of a full-fledged autopilot for private cars. However, there are a lot of technological and legal issues to be resolved, so whether this will happen shortly is not clear.
Smart fiber sensors for security
One of the most popular and well-developed features of smart cities today is the security (in the context of protection from crime). The streets of cities around the world are equipped with video surveillance cameras connected to a single fiber optic system for collecting and processing information, which reduces the volume of crimes. But video surveillance is just one part.
Smart policing is an attempt to transform a familiar service into a more effective law enforcement tool in the face of increasing population density. There is a huge layer of fiber optic technologies that the average user simply does not notice. In addition to the video surveillance system itself, this may include:
● new communication tools that allow quickly receiving information about incidents;
● modern emergency notification systems for employees and the public;
● equipment (sapper robots, drones, etc.) that allows replacing people when they have to solve dangerous tasks or improve search and other activities;
● data collection tools that can be used as an evidence base (audio recording, etc.);
● fiber optic systems for analyzing all kinds of data that allow identifying atypical human behavior or infrastructure failures at an early stage.
In the future, the concept of smart police implies the creation of centers, where all the information is collected by the fiber optic systems, especially from critical areas. Seeing the whole situation, emergency services can make decisions more quickly.
Fiber optic sensors for smart resource consumption
It is obvious that accurate accounting of resources consumed allows managing the load or making savings. Therefore, it is necessary not only to implement fiber sensors in all areas of housing and communal services but also to collect data in a single platform for centralized management. On the scale of the entire country, this is a task for years and it requires billions of dollars in budgets.
There are examples of cities around the world that are actively implementing smart resource consumption. In particular, Barcelona has introduced automated structural health monitoring of street lighting, taking into account the time of day and weather conditions. Taking into account favorable environmental conditions, solar energy is actively used here for heating water in buildings, as well as powering interactive displays of public transport stops. Nowadays a modular open-source platform is being developed. It collects and analyzes information from fiber optic sensors for the consumption of basic resources, weather fiber sensors, ambient noise, etc.
Other areas as part of the smart city
Smart education and health care (as well as other areas — mass events and tourism) allow not so much to save money but to improve the quality of life in the city. Broadband networks make it possible to significantly expand the audience listening to a particular training course. For this purpose, educational facilities are equipped with electronic boards and cameras, as well as remote presence systems. This allows solving different tasks at different levels of education — from providing compulsory secondary education to low-mobility citizens to remote higher education in the country’s leading universities.
Similar fiber optic systems in medicine allow helping patients in hospitals on the outskirts or in the regions, using the advice of more qualified specialists from the center. For example, it can be performed by a mobile carriage with diagnostic devices, a computer, a video camera, etc.
It is worth noting that the division of industries in this list is very conditional. Many tasks are solved at the intersection of, for example, resource analysis and logistics. The routes of cars that take out the garbage are planned not according to a schedule, but taking into account the data from the fiber optic sensors. They detect the fullness of garbage containers that arrive at the coordination center in real-time.
Besides, some ideas combine fiber optic solutions from several areas at once. For example, they include smart office buildings that are part of a smart city.
The main problems of implementing fiber optic sensors
From the business point of view, there are several serious obstacles to the development of real projects within the framework of the smart city concept, which still need to be improved. Individual components of the smart city have been developing in different cities for a long time. The main problem is the payback period for projects.
Therefore, the first task is to increase the level of security in cities, obviously, through the introduction of video recording systems and video analytics provided by fiber sensors. It allows automatically cut off a large part of street crimes. This is the most understandable task: it is clear how to use fiber optic technology and why it is necessary, it is easier to justify the costs.
In general, local specifics are extremely important for the smart city project, because people think differently in every city in the world, they have different needs and problems.
The issue of the security of the smart city system itself requires special mention. After all, every smart fiber sensor or device can become an entry point for intruders. The sensor software can be modified so that if there are “defects” in the security system, it will perform completely different tasks.
Usually, all fiber optic sensors are made in the dust- and moisture-proof coatings, equipped with batteries with a long working time, and support data transmission over the network.
Finally, it is necessary to pay attention to the fiber sensor for monitoring the position of manhole covers and the water level sensor, which allows measuring the water and its volume in any tank.
Smart cities are predicted to have a great future. However, when it will come, it is not yet clear. The thing is that technologically, everything is ready for this. There are Big Data analysis tools, appropriate server equipment, fiber sensors that can work for ten years without recharging the battery, and appropriate communication standards. Nevertheless, this market has a lack of technological stability — the final choice of dominant standards and the formation of business models. All these help to understand how you can work and earn money here.
A group of scientists from China has designed a very sensitive tiny fiber optic sensor for the measurement of the slightest pressure changes. Such FBG pressure sensors are suitable for medical applications. Herewith, they do not have numerous disadvantages of silica-based optical fibers.
According to scientists, such a fiber sensor is extremely sensitive, and it allows for measuring lung pressure even while breathing. The thing is that pressure changes in the lungs are very small and difficult to be detected. The operating principle of FBG pressure sensors is based on a fiber Bragg grating (FBG) inscribed into an optical fiber.
It should be noted that the optical fiber used is made of a new polymer. The pressure sensor detects the slightest pressure changes of 2 kilopascals. The biocompatibility of these fiber optic sensors makes them suitable for medical applications. Additionally, the fiber sensors are chemically inert, herewith they are not sensitive to moisture.
The scientists plan to use FBG pressure sensors to control different parameters that contain pressure, temperature, and strain. Moreover, numerous modern fiber sensors use FBG technology, “ tiny periodic microstructures that can be inscribed onto a fiber.”
FBG sensors made of conventional silica-based fibers have several disadvantages for medicine. They are not convenient for long-term use in the body because these optical fibers are relatively hard and very frangible. Moreover, most FBG sensors made of silica perform limited sensitivity to the slightest pressure changes.
Compared to silica sensors, there are polymer fiber optic sensors. However, they absorb water. This is the main reason why scientists create advanced polymer optical fiber to solve the current problems. Novel FBG pressure sensors can be applied in aqueous environments.
Also, such material offers a higher light shift in response to a pressure change. The production of these FBG sensors becomes easier because it doesn’t require the use of dopants. Thus, scientists produce optical fibers with good reproducibility.
The FBG pressure sensors have been already tested by comparing their performance with the standard polymer counterpart. Herewith, novel fiber sensors provide a linear, repeatable response. They can be employed for low-pressure measurement up to 50 kilopascals above or below atmospheric pressure with a resolution of 2.0 kilopascals.
Finally, these FBG sensors demonstrate higher sensitivity (80% higher than standard polymer-based sensors). Their promising applications include the operation not only in medical and high-altitude environments but also in gaseous containers.
Nowadays researchers tend to use fusion as a safe energy source at power plants. Nevertheless, this process is dangerous. It requires reliable fiber optic technology for structural health monitoring at power plants. Novel fiber optic sensors offer robust operation in the harsh conditions of a commercial fusion power plant.
To be more precise, these fiber sensors provide temperature sensing applying optical fibers with written fiber Bragg gratings (FBGs). The FBG operating principle is based on broadband light that is directed on it. Although most of the light goes through, one wavelength is reflected. Herewith, the reflected wavelength changes with both temperature and strain.
Therefore, the installation of several fiber Bragg gratings enables performing independent temperature sensing of each location. Standard FBGs are widely used in various industries for strain and temperature sensing. Herewith, compact superconducting cables use these optical fibers based on fiber optic technology.
Novel FBG sensors can maintain “the intense electrical, mechanical, and electromagnetic stresses of a fusion magnet’s environment.” The novel fiber optic technology supposes ultra-long fiber Bragg gratings of 9-millimeter located 1 mm apart. The FBG sensors operate as conventional long quasi-continuous systems.
Compared to standard systems, FBG sensors include such benefits as long grating length (meters instead of millimeters). Ultra-long FBGs allow for sensing simultaneously occurring temperature changes along their entire length. Thus, it is possible to determine fastly temperature variation, irrespective of the location of the heat source.
Additionally, it is possible to combine ultra-long FBGs and traditional FBGs to produce both spatial and temporal resolution. The fiber optic technology has been developed by a team of researchers from Switzerland. According to them, such a combination can be used on bigger cables.
These FBG sensors detect quickly and accurately even the smallest temperature changes under realistic operation conditions. Moreover, they demonstrate a better signal-to-noise ratio thanks to their high level of sensitivity and the opportunity to adjust the optical fiber response.
Thus, the fiber optic sensors locate quench events tens of seconds faster than voltage taps. Herewith, the application of FBG sensors for HTS magnets quenches detection is very potential. It allows for overcoming the current problem of HTS coils from damage during quenches.
Finally, such a fiber optic technology plays a crucial role in compact fusion processes, where practical, high-field, high-temperature superconducting magnets are important. FBG sensors are still under development and need some improvements to be used in new applications.
Common communication channels apply fibers in fiber optic sensors where laser beam light passes along haul distances. These fiber sensors allow for determining, controlling, and measuring external parameters in a distributed format. Herewith, the optical fiber in a fiber optic system operates both as a distributed transducer and optical channel.
To be more precise, the fiber optic sensors measure various changes on specific parameters along with the transducer. Such factors as the dynamic range and the spatial resolution play a crucial role in distributed sensing but still have to be improved. The operating principle of fiber optic systems is based on “the incident light wave that produces acoustic waves through the electrostriction effect. It induces a periodic modulation of the refractive index of material that evokes a light-backscattering like a fiber Bragg grating of FBGs.”
It should be noted that a fiber sensor or sensing system is a tool that determines, measures physical or chemical parameters. Herewith, in the case of light use in such systems, this is a photonic or optical sensor. The fiber optic sensors, in turn, consist of optical fibers and the fiber optic technology around them.
Distributed fiber optic sensors detect and measure physical factors by Brillouin scattering of light in optical fibers. Brillouin scattering advances the development of precise distributed fiber optic systems. Additionally, these fiber sensors enable to measure specific variables.
Distributed sensing systems are very promising for structural health monitoring. The following parameters can be detected: strain and temperature, acoustic waves, and others. Moreover, these fiber optic sensors maintain severe environments and offer noise electromagnetic immunity, durability, and reliability.
The most common application of fiber sensors based on the Brillouin sensing technique includes laboratory implementation. Nevertheless, their applications are not limited to labs only. Distributed fiber optic sensors are widely used in such fields as:
The civil infrastructure where distributed sensing systems detects variables in bridges, railways, and land monitoring;
Bridges and monitoring where compact fiber sensors promote accurate diagnostic load test;
Geotechnical structures monitoring for measuring and controlling of the stress distribution;
Pipelines monitoring by distributed fiber optic sensors in real-time for early warning of liquid and gas pipes;
Monitoring of some materials and structures, for instance, competition yachts or experimental vehicles.
Nowadays fiber optic solutions play a crucial role in information technology. Fiber optic technology promotes the development of advanced fiber optic sensors. These fiber sensors offer numerous benefits that make them very attractive. The benefits include “durability, flexibility, biocompatibility, high sensitivity, and electromagnetic interference immunity.”
The applications of fiber optic sensors consist of numerous fields. They are widely used in medicine, environmental protection, industrial production, and structural health monitoring. Herewith, different types of fiber sensors allow for measuring various physical and chemical parameters. For instance, they sense temperature, acoustic, pressure, humidity, and others.
The production of distributed sensing systems requires different types of fibers. The following types are the most popular: photonic crystal, polarization-maintaining, double-core, sapphire optical fibers, etc. It should be noted that various fiber optic sensors use various measurement principles. Additionally, fiber Bragg gratings (FBGs) – the most popular measurement principle.
FBG sensors can also perform multi-parameter measurements to meet the practical demands of scientists. Thus, a team of researchers has demonstrated a cascaded multi-mode FBG sensor that performs the dual-parameter measurement. They apply optical fiber with several modes to create a distributed sensing system. Moreover, the FBG sensors measure the Brillouin frequency shift for temperature and strain sensing.
To be more precise, these FBG sensors have a hybrid structure (FBGs and FPI) with a nano-silica diaphragm on the tip. Besides, the total length of the fiber sensor is less than a human hair. These FBG sensors determine both environmental temperature and pressure. Therefore, such a fiber optic solution is highly promising in specific applications in severe environments.
Finally, the hybrid fiber optic sensor has been already produced and even tested. The distributed sensing system includes an FPI with a silica diaphragm. Also, fiber optic technology applies the femtosecond laser inscription technique and arc discharge methods. These FBG sensors demonstrate a high level of pressure and temperature sensitivity.
Additionally, the fiber optic sensor has an ultra-low level of cross sensitivities. “The temperature-induced error of the pressure measurement was –1.4286 kPa/ and ℃ pressure-induced error of the temperature measurement was ~0℃/MPa.” The mentioned-above benefits of FBG sensors make them perfect for numerous fields of applications.
A novel fiber optic technology developed by researchers from Singapore becomes the basis for a novel fiber sensor for plant detection. The fiber optic sensors perform both detection and real-time monitoring of arsenic levels in underground environments. Such monitoring by distributed sensing systems is very important because it shows the presence and quantity of the metal.
The operating principle of this fiber optic system is based on the plantation of fiber sensors into plant tissue. Thus, fiber optic technology allows for detecting arsenic as low as 0.2 parts per billion. Compact and low-cost electronics records data. To be more precise, the combination of fiber optic sensors and plants operate as a fully functional environmental detection system.
It should be noted that such fiber optic systems can be useful in environmental monitoring and agriculture. The thing is that arsenic is a widespread contaminant in most crops, so its detection is crucial for structural health monitoring. Additionally, it is dangerous for human health because it causes cardiovascular disease and even cancers.
It is possible to tune selectively these fiber optic sensors to detect particular arsenic quantities. Herewith, the nanotubes used in fiber sensors do not photobleach, therefore, they have stable emission over time. These fiber optic systems are safe for plants in which they are installed. The technology has been already tested and demonstrated great improvement in time- and equipment-intensive sampling techniques.
“The newly demonstrated technique benefits from the natural ability of plants to extract analytes from their roots and move them throughout their body.” The fiber optic sensor embedded in the living plant presents perfect operation. The researchers use a camera in the fiber optic system to obtain real-time imaging and analysis. Herewith, this fiber sensor can be controlled with compact low-cost electronics.
The tests have been already carried out on spinach and rice, as well as a species of fern. Some properties of fern species promote optimizing the fiber optic sensors to locate extremely low concentrations of arsenic. Compared to the novel fiber system, conventional sensors have a 10 ppb limit.
Thus, fiber optic technology enables the development of more resistant crops to toxic contaminants. The researchers claim that it is possible to transform any living plants into fiber sensors for arsenic detection. Now it is planned to create a compact, portable fiber optic system to control the fluorescence of the sensors within the plants. Finally, novel fiber optic sensors are highly reliable no only in labs but also under field conditions.
A team of scientists from Israel and Russia has developed a novel, straightforward, and low-cost fiber optic technology. It allows for the testing of liquid biological samples. Herewith, the developed fiber optic system is very promising in clinical settings, containing real-time testing during surgery.
To be more precise, fiber optic sensors are widely applied in the healthcare system for real-time diagnostic testing for biological samples. The fiber sensors offer a high level of sensitivity, however, usually “that sensitivity comes at a cost in terms of time and resources.”
Therefore, scientists tend to create simple, inexpensive fiber optic sensors as a more efficient alternative. It should be noted that they pay careful attention to the optical dispersion of the refractive index of a sample. The thing is that this process of the fiber optic system operates as a fingerprint of sorts that controls the changes in its composition.
Thus, the team has presented the concept of multispectral fiber optic sensing for liquid biological samples in both static and real-time modes. Herewith, fiber optic technology is accurate, robust, and highly sensitive to impurities in the sample. These fiber optic sensors will be helpful for diagnostic applications and real-time simulations of different biological processes.
The fiber sensors include hollow-core microstructured optical fibers. It is a specific type of optical fiber that keeps light inside a hollow core of the fiber optic system surrounded by microstructured cladding. Liquid passes through champers of fiber sensors, and the team registers spectral shifts of maxima and minima in the transmission spectrum.
These signals show the chemical composition of the sample. Additionally, the fiber optic sensors do not require an external cavity or interferometer. This is the main reason why fiber optic sensing is straightforward and virtually cheap to create. Such fiber optic technology has been already tested by scientists.
The fiber sensors test the concentration of bovine serum albumin, generally applied in such experiments, dissolved in water and phosphate-buffered saline solution. The fiber optic system demonstrated a resolution similar to the accuracy of standard albumin tests and complied with clinical requirements.
The potential application of these fiber optic sensors includes the analysis of biomarkers of various types. It is necessary to test the fiber sensors on other bioanalytics and then modify them to enhance specificity. The fiber optic technology opens new opportunities ina fast, inexpensive and robust analysis of blood and other bodily liquids in real-time.
A team of scientists from Denmark in a collaboration with chemical engineers has presented novel accurate fiber optic sensors. They allow for significantly decreasing the level of air pollution. The operating principle of this fiber sensor is based on modern telecom technology. It helps to detect and measure ammonia in the atmosphere by the sensing system, a laser, and hollow-core optical fibers.
To be more precise, the fiber optic system provides continuous ammonia monitoring for agricultural application. Additionally, the fiber optic sensor can be created at a pretty low cost. The benefits of fiber sensors such as compact size, high reliability, and low cost meet the requirements of a portable system for detecting ammonia.
It should be noted that such a fiber optic technology is still under development. The thing is that the sensitivity of the fiber sensor requires improvements, which scientists try to perform. Even though the main purpose of the new sensing system is ammonia detection, it is possible to use fiber optic sensors for the detection of other gases, for instance, greenhouse gases.
Moreover, fiber optic technology operates as a part of one agricultural project. In this project, scientists develop new techniques and technology to measure and reduce air pollution from the agricultural sector. Nowadays the agricultural sector is considered to be the main contributor to air pollution (mainly caused by ammonia). Therefore, agricultural pollution is the biggest environmental issue that requires efficient fiber sensors.
The thing is that now ammonia emissions are challenging to measure at the farm level. Compared to novel fiber optic sensors, traditional systems for ammonia detection have a high cost. Fiber optic technology is very promising with great prospects for agriculture. “The ability to continuously and cost-effectively track the development in ammonia emissions from agriculture offers completely new opportunities for the industry to experiment on decreasing the emissions.”
Scientists claim that there are already established figures considering air pollution from agriculture. Nevertheless, the future potential of fiber optic sensors may greatly transform the detection way of ammonia caused by agricultural farms. The new fiber optic technology promotes farmers to control their emissions continuously.
Finally, precise monitoring of ammonia emissions provided by sensing systems makes streamline operations far better. Thus, fiber sensors lead to emissions-based regulations that help reduce the environmental impact of agriculture. The development of these fiber optic sensors will continue until the next year.