#opticalfibers fiberoptics medicine medical fibers

[optromix]

Endoscopic fiber catheter and its applications

An endoscope is an optical device that is used to study hard-to-reach cavities of mechanisms, machines, and equipment. In its simplest form, it is a long flexible or rigid fiber bundle with a lens, optical system, illumination, and eyepiece. In the case when the optical fiber is used for image transmission, such an endoscope is called a fiber optic one, fiberscope or endoscopic fiber catheter.

Light is used to transmit electronic signals over long distances. A single fiber bundle with a thickness of human hair can transmit all the signals necessary for the operation of televisions, telephones, and computers at home or in an institution. Such fibers, also called optical fibers, are usually made of glass or plastic.

The main element of a fiber optic cable or simply optical cable is an optical fiber waveguide. A fiber waveguide, or optical fiber, is an optical waveguide designed for the directional transmission of optical radiation, made in the form of a thin glass bundle of a cylindrical shape with a circular cross-section.

The optical fiber consists of a light-transmitting core, one or several layers of protective-reflective coatings, which prevent the diffusion of light. The fibers are collected in a cable, which can contain from 72 to 144 fibers.

Cables based on fiber optic technology are used in medical equipment and instruments. Standard technology includes the opportunity of inserting a special tool with flexible optical fibers, which can transmit a signal to an external camera inside the organs of the human body. Fiber optics is used in medicine as lighting material. Devices equipped with fiber modules allow painlessly highlighting the cavity of the stomach, nasopharynx, etc.

Modern endoscopic fiber catheters have a fairly complex scheme, which includes the following elements:

● fiber optic probe with stainless steel coating and tungsten covering;  

● fiber optic light guide to provide illumination and light transmission from the source to the distal end;

● lens, interchangeable optics;

● eyepiece;

● body frame.

The design may vary depending on the purpose of use. So, for those cases when it is necessary to use ultraviolet illumination, the optical fiber with quartz fibers are used. The endoscopic fiber catheter must be absolutely dust-proof and waterproof, as well as resistant to aggressive environments, oils, gasoline, etc. The camera can be connected to the eyepiece through a special adapter for recording and documenting, as well as a display.

Endoscopic fiber catheters have a very wide range of applications. Due to the design features and the principle of operation, devices with a fiber optic probe diameter of up to two millimeters are produced, which allows quality control of internal surfaces and hidden cavities of almost any objects to which access by other means is practically impossible: turbines, aircraft wings, heat exchangers, pipelines and pipes of small diameter, etc.

Endoscopic fiber catheters, like their gradient, lens counterparts, are also commonly divided into two very broad categories. The first includes flexible endoscopes (the manipulator of such optical fiber devices can bend at any angle). The second includes devices of rigid type (the manipulator is straight and inflexible). It is flexible endoscopic fiber catheters that are used more actively and are in high demand for obvious reasons. And that's all, even despite the higher price of such equipment.

A rigid endoscope (fiber optic bundle) consists of visual and lighting systems. The visual system consists of a lens, rod or gradient optics, which is enclosed in an internal metal tube. The lighting system consists of an optical fiber that is located between two metal tubes: external and internal.

Rigid endoscopic systems are characterized by four main parameters: the diameter and the length of the working parts, the angle of the observational direction and the angle of the view field. The main advantage of rigid endoscopes is their high resolution - up to 2S lines per millimeter.

Direct access to the object is not always possible or the object itself has complex geometry, for example, gas turbines, electric engines, turbogenerators, boilers, heat exchangers, water pipes, sewers, industrial communications. In this case, flexible endoscopic fiber catheters are used for visual inspection.

The visual system and the light transmission system in flexible endoscopes consist of fiber optics mounted inside a flexible fiber bundle with a controllable distal end.

Flexible endoscopic fiber catheters have a controlled distal end that bends in one or two planes. As a rule, this is determined by the diameter of the working part. The main disadvantage of flexible optical fiber endoscopes compared to rigid ones is lower resolution. It is necessary to pay attention to two main parameters when choosing flexible endoscopic fiber catheters: diameter and length of the working part. 

However, choosing a fiber optic endoscope, you will need to pay attention not only to the flexibility or rigidity of its manipulator but also to whether the case of such a product is waterproof. Resolution is also important. By the way, it is the resolution that is a very important indicator, and therefore it’s worthwhile to research this parameter in a little more detail. By simple and understandable words, the higher the resolution is, the better the quality of the image produced by the endoscopic fiber catheter is considered to be, herewith, such a fiber optic device will be more useful to your needs and the needs of your enterprise.

The main purpose of optical fiber endoscopes is a quick and high-quality visual examination of hard-to-reach cavities of machines and mechanisms without disassembling them. The most illustrative examples by industry are shown below.

● Power industry - endoscopic fiber catheters monitor the state of heat engineering, electrical and other types of power plant equipment. For example, they are used to monitor the condition of the intra-cooling channels, the windings of electric generators and transformers, the inner walls of the pipes.

● Water supply and sewage - optical fiber endoscopes detect damages, corrosion, blockages, cracks and foreign objects in pipes and tanks, they monitor the flowing part of pumping systems.

● Metallurgical industry - fiber catheters are applied for the maintenance of production facilities, for example, inspection of furnace assemblies, as well as for quality control of forming.

● Aviation and space industry - fiber optic sensing systems monitor the state of power elements of hull structures, tank walls, gas turbine blades and compressors, shells, sprayers, nozzles of combustion chambers, as well as they participate in the development and production of rocket engines and pneumatic hydraulic systems.

● Mechanical engineering - endoscopic fiber catheters control the quality of manufacturing and check the technical condition of various components and parts of machines, for example, mold cavities, mechanical transmission parts, bearings, pipelines, soldered and welded structures cavities.

● Security services, customs - fiber catheters are used for the quick search for explosive devices, drugs, weapons, smuggling, for inspecting the contents of opaque containers without opening them, and for a number of other special purposes.

● Architecture and construction - fiber optic bundles check the state of power elements of ceilings, internal cavities, reinforcement and waterproofing of walls, condition of pipelines, as well as architectural modeling.

● Gas pumping stations - fiber sensing systems monitor the condition of the blades, combustion chambers, fuel system and other components of gas pumping units, they check for erosion, corrosion, deposits and fatigue cracks in taps, valves, pipelines, separators, and other systems.

● Chemical and petrochemical industry - optical fiber catheters perform systematic and emergency inspections of pipelines, pressure vessels, heat exchangers, pneumatic and hydraulic units and other devices.

● Automotive industry - they control the quality of manufacture and assembly of engines, for example, the quality of cleaning forming from rods, control hydropneumatic systems, the quality of welding and painting. In operation - sensing systems for monitoring the condition of valves, cylinder liners, gear, corrosion of body parts.

● Rail and sea transport - fiber optic catheters for inspection of diesel and electric engines, generators, transformers, and other units and assemblies.

● Electronic industry - fiber bundles control and ensure the quality of production and assembly of electronic devices.

● Science and education - the systems are employed for observing animals and insects, studying the root system of plants, etc. They include archaeological and exploratory work, an inspection of the internal cavities of statues and monuments.

Medicine

The benefits of optical fibers in medical fiberscopes

Modern endoscopic sensing systems (flexible endoscopes, fiberscopes) use fiber optics. Almost all organs became available for inspection by endoscopic fiber probes, the illumination of the organs under investigation increased, conditions for photographing and video recording (endophotography and endocinematography) appeared, and it became possible to record images on video (on external systems). Currently, endoscopic fiber techniques are used for both the diagnosis and treatment of various diseases.

If you would like to obtain an optical fiber product, you should choose the Optromix company. Optromix is a provider of top quality special fibers and broad spectra fiber optic solutions. The company delivers the best quality special fibers and fiber cables, fiber optic bundles, spectroscopy fiber optic probes, probe couplers and accessories for process spectroscopy to clients. The Optromix product line is based on over 30 years of unique technology experience, which allows these products to have a broad spectral range from 200 nm to 18 µm.

Optromix optical fibers are used in a wide variety of applications, some of which include spectroscopy and process monitoring tasks, IR radiation delivery to and out of closed volumes, thermosensing, laser power flexible delivery systems, IR-imaging, etc. Along with a regular range of products, the company offers custom optical fiber solutions for non-standard tasks and applications. The aim is to deliver the best quality optical fiber systems, high power fiber cables, and spectroscopy fiber probes & fiber bundles to clients, and our custom solutions meet the needs of a wide range of applications, such as reaction monitoring, biomedicine & biotechnology, IR-Fiber pyrometry, laser technology. If you have any questions or would like to buy an optical fiber, please contact us at info@optromix.com

[optromix]

FBG sensors: a comprehensive review

A fiber Bragg grating is an optical interferometer embedded in an optical fiber. At the same time, fiber optics combined with certain substances (usually germanium) can change its refractive factor when the fiber is exposed to ultraviolet light. If such a fiber is illuminated with ultraviolet light with a specific spatial periodic structure, the optical fiber becomes a kind of diffraction grating. In other words, this optical fiber will almost completely reflect the light of a certain, predetermined range of wavelengths, and transmit light of all other wavelengths.

The FGB application includes the following fields:

• Point sensors (that is able to measure deformation, temperature, pressure, tilt, displacement), embedded in composite materials and others;

• Laser systems and amplifiers (filters, mirrors);

• Telecommunications (dispersion compensation modules, WDM technology);

• Research and development.

For decades, electrical sensors (tensor-resistive, string, potentiometric, etc.) have been the main method of measuring physical and mechanical phenomena. Despite their widespread use, electrical sensors have several disadvantages, such as loss during signal transmission, sensibility to electromagnetic interference, the need to organize a spark-resistant electrical circuit (if there is a danger of explosion). These mentioned above limitations make electrical sensors unsuitable or difficult to use for a number of applications.

The use of fiber optic sensors is an excellent solution to these problems. In fiber optic sensors, the signal is light in the optical fiber instead of electricity in the copper wire at traditional electrical sensors.

Over the past twenty years, a huge number of innovations in optoelectronics and in the field of fiber optic telecommunications has led to a significant reduction in prices for optical components and to a significant improvement in their quality. This factor allows fiber optic sensors to move from the category of experimental laboratory tools to the category of widely used devices in various areas.

A fiber Bragg grating or FBG acts as a sensitive element of point fiber optic sensors, which is capable to reflect certain wavelengths of light and transmit all others.  This effect is achieved by periodically changing the refractive index in the core of the fiber optics.

When the laser light passes through an optical fiber, a part of it is reflected from the fiber grating at a certain wavelength. This peak of reflected light is registered by measuring equipment. As a result of the numerous parameters influence, the interval between the FBG bundles and the refractive index of the fiber optics change.

Consequently, the wavelength of the light reflected from the fiber Bragg grating changes. In addition, it is possible to determine the exact characteristics of the changes by changing the wavelength. In fiber optic sensors based on Bragg gratings, the measured value is converted to a Bragg wavelength offset. The recording system converts the wavelength offset into an electrical signal.

The sensing element of such FBG sensor does not contain electronic components and therefore it is completely passive, which means it can be used in the area of increased explosiveness, aggressiveness, strong electromagnetic interference. Numerous fiber Bragg gratings can be installed on a single fiber, each of which gives a response at its own wavelength. In this case, instead of a point sensor, we get a distributed sensing system with multiplexing along the wavelength.

The use of the light wavelength as an information parameter makes the FBG sensor insensitive to the long-term changes of the parameters of the source and radiation detector, as well as random attenuation of power in the optical fiber.

The following types of fiber optic sensors  based on FBG technology are used for automated monitoring:

FBG strain sensors;

FBG displacement sensors;

FBG temperature sensors;

FBG pressure sensors;

Fiber optic tilt sensors;

Fiber optic acceleration and vibration sensors;

Data recorders for fiber optic sensors;

Additional equipment for data recorders.

The principle of FGB sensor operation is based on the modulation of one or several properties of a propagating light wave (intensity, phase, polarization, frequency), which change occurs with a change in the measured physical quantity.

The basis of fiber-optic sensing technology is optical fiber - a thin glass thread that transmits light through its core. The optical fiber consists of three main components: core, shell, and coating. The shell reflects the scattered light back into the core, allowing light to pass through the core with minimal loss.

It can be achieved by a higher refractive index in the core relative to the shell, resulting in a complete internal reflection of light. The outer coating protects the fiber optics from external influences and physical damage. It can consist of several layers depending on the required protection.

The advantages of FBG sensors include:

• Wide sensing range;

• Possibility to integrate the FBG sensing system into the object structure;

• Full fire and explosion safety;

• Long distance signal transmission;

• Integration of several fiber optic sensors in one channel;

• Insensitiveness to electromagnetic and radio frequency influences;

• No need for recalibration (stable over time under constant external conditions).

At the moment, most of the sensors used in the world are electrical sensors. As it was mentioned above, in optical sensors based on fiber Bragg gratings, the signal is light passing through an optical fiber (instead of an electric current passing through a copper wire). This fundamental difference allows FBG sensors to overcome many problems typical for electrical sensors.

Optical fibers and sensors are non-conductive, electrically passive and immune to electromagnetic interference. Monitoring with a tunable high-power laser system allows sensing over long distances with virtually no signal loss. In addition, each optical channel is able to monitor a variety of FBG sensors unlike the electrical channel, which significantly reduces the size and complexity of such a sensing system.

Optical sensing systems are ideal for use in conditions where conventional electrical sensors (strain gauge, string, thermistor, etc.) can be difficult to use (long distances, EM fields, explosion safety, etc.).  It is easy to switch to fiber optic solutions since the installation and operation of optical sensors are similar to traditional electrical sensors.

Understanding the principles of FBG operation and the benefits of Bragg grating sensor application can greatly facilitate the solution of various problems in the field of sensing measurement (for example, monitoring of structures).

Nowadays FBG sensors are applied in various fields that require precise and fast measurements. Fiber Bragg sensing systems can be used in aeronautic, automotive, civil engineering structure monitoring, undersea oil exploration, in the mining industry, geotechnical engineering, structural engineering, tunnel construction engineering, etc.

The most promising application of FBG sensors is medicine. Now FBG technology is highly used for fiber-based biomedical sensing including biosensing, safety or security, and structural health monitoring. FBG sensors offer a new and effective way of real-time measurements. They can be applied in laser systems, medical tiny intra-aortic probes and body sensors for biochemical analysis making. For example, today fiber Bragg gratings apply optical-fiber sensing probes that are able to dissolve due to such ability as controlled solubility in a physiological environment. Thus,  FBG technology enables safer diagnostic of sensitive human organs and there is no need for a surgical extraction. The development of FBG continues, and it is possible that very soon new FBG sensors with improved characteristics appear. If you want to obtain a highly efficient sensing system, you should choose Optromix company. Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for monitoring worldwide. Optromix is a fast-growing vendor of fiber Bragg grating (FBG) products line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, distributed acoustic sensing (DAS) systems, distributed temperature sensing (DTS) systems. If you are interested in FBG sensors and want to learn more, please contact us at info@optromix.com

[optromix]

Medical application of optical fibers: a detailed review

Optromix is a provider of top quality special fibers and broad spectra optical fiber solutions. The company delivers the best quality special fibers and fiber cables, fiber optic bundles, spectroscopy fiber optic probes, probe couplers and accessories for IR fiber spectroscopy to clients. The specialty optical fibers and fiber systems are based on over 30 years of unique technology experience. If you have any questions, please contact us at info@optromix.com

The optical fiber is an elongated thread made of glass or transparent plastic. At first glance, this is a quite simple system, but in practice, it has a number of serious problems that limit fiber optic application.

The first problem is a signal attenuation in fiber optic lines. Actually, the solution is known for a long time that makes it possible to develop fiber-optic networks. Nevertheless, networking is not the only field of fiber optic application where optical fibers can be applied.

The solution for the second problem that is polarization saving requires the creation of anisotropic fiber cladding: the inner part of the cladding has a different width and height (an elliptical shape), which leads to the different speed of light propagation with different directions of field oscillations.

It should be mentioned that fiber optic cable is also used in numerous application fields. However, its most important application is medicine. The optical fiber is very often used in medicine for diagnosis.

An unordered fiber optic bundle can be used for illumination during an operation,

and an ordered one can transmit an image to the screen. Herewith, the use of ordered fiber optic bundles is based on this exact function. Approximately the same principle underlies the process of optical fiber welding.

Another physical quality of the optical fiber is also extremely important from a medical point of view: fibers are highly flexible and this makes it possible to apply a laser beam in therapy. So, optical fibers help laser systems in almost all types of therapy, in which the high-quality laser beam should penetrate the human body: in pulmonology, urology, gynecology, etc.  In the cases, when energy from laser systems is directed into the bloodstream, catheters made of fibers are used.

It should be noted that in medicine only optical fibers made of high-frequency quartz glass are used since the high mechanical strength and the adjusted optical properties make it possible to adjust the light loss in an optical cable.

Since optical fibers are able to be very thin and can be twisted into flexible threads,

they can be applied in researches of blood vessels, lungs, and other human organs. Optical fibers allow doctors to make visual analysis and treatment of various diseases through very small incisions using an endoscope.

An endoscope is a medical instrument made to insert two optical fiber bundles into one long tube. One bundle of optical fiber is used to project light onto inspected tissue areas, while the other optical fiber transmits reflected light from tissues and produces a clear image. Endoscopes are used to study specific areas of the human body. For example, doctors can use an endoscope to examine the knee, shoulder, and other joints in the body, without any danger to health.

Another research method that uses fiber optics, and is widely applied for the treatment of various diseases is arthroscopy. In this method, an arthroscope is used. Optical fibers in the arthroscope allow measuring temperature and other body parameters, as well as during surgical procedures. The main benefit of fiber optics is that the operation can be performed through a small incision, as a result of which the patient experiences the least inconvenience, and the healing time is significantly reduced compared to other surgical methods. In addition to endoscopy and arthroscopy, the application of optical fibers includes the research and treatment of the heart and blood vessels.

Also, doctors have successfully applied optical fiber to direct intense laser radiation on a wound, to stop bleeding or burn abnormal tissue. Fiber optic research is urgently needed in the medical field because the application of optical fibers in the medicine and researches continues to grow rapidly with each passing day.

The new system allows almost instantly detect the presence of certain substances, which are "markers" of a particular disease in human blood. The fiber optic technology is still being developed, but the first prototypes have already shown the broad capabilities of the new system.

Flexible optical fibers are used to study bioelectric current both in contact and non-contact ways. During non-contact use, laser radiation does not touch tissue. Thanks to focusing elements, the radiation focuses on a very small area of skin that is much smaller than the diameter of the fiber optic itself. If the quartz fiber touches the tissue, this method of application is contact. Moreover, it is necessary to have the qualification of a surgeon in order to properly use the fiber in medicine.

Herewith, ordinary glass fibers can be used for endoscopic purposes. This is due to a tiny diameter (about 0.5 mm-1 mm). Sometimes the mechanical cover is also specially removed at the end of the fiber. Herewith, this type of application has a special name - "bare fiber". If a bare fiber is put to the biological tissue by a contact method and the tissue is irradiated with small laser power, a clearly defined zone appears in which the laser radiation is completely absorbed and, as a result, the tissue disappears.

In some cases, metal tips or so-called “heating probes” are put on the fiber. Due to them, laser radiation turns into heat and penetrates the tissue more accurate through the hole in the fiber probe. Also, surgeons use pointed sapphire tips, which, due to a special form, very strongly concentrate radiation and literally cut through the tissue. Of course, such operations are quite expensive, because the cost of fiber welding depends on many conditions.

Nowadays the study of optical fibers is one of the most developing spheres in optics. Numerous technological solutions have been invented and implemented over the past decade. So, today it is possible to create fiber threads of almost any thickness with an arbitrary transverse structure.

However, medicine is not the only application field of fiber optics. It is used as the mean of data transmission in telecommunication networks. Also, optical fibers are utilized for the network creation of different levels. The field of their application is so wide that they help you to create both a simple home network and a single channel of information transfer for the whole country.

Such popularity of optical fibers is explained by its high protection from outside penetration, low level of signal attenuation, the ability to transfer data over long distances with ultra-high speed. This is what made it possible to use optical fibers for the creation of an intercontinental external communication channel. This fact explains the demand for fiber optic cables. The data transfer rates in fiber optic networks can be very high. For example, there are fiber optic networks that are able to transmit information at speeds up to 1 Tbps.

The optical fiber is the compound of fiber-optic sensors that are ideal to measure voltage, temperature, pressure, and numerous other parameters. They are popular due to their simplicity and low energy costs.

Optical fibers are used in hydrophones, in seismic and sonar devices. Several fiber-optic sensors fixed on one cable can organize complex systems. The pressure and temperature sensors are used for measurements in oil wells, where the depth reaches thousands of meters. This is due to the fact that the pressure in the earth’s thickness increases significantly that causes semiconductor sensors to fail, while fiber-optic sensors function well in similar conditions.

Fiber-optic sensors are also used in devices for arc protection. Their main advantages are high speed, immunity to electromagnetic effects, flexibility, ease of installation and dielectric properties.

The application of optical fibers includes lighting. This is especially useful during work in dark, hard-to-reach areas where bright light is necessary for effective work. Also, a fiber optic can be seen in an outdoor advertisement, it attracts people's attention with light effects.