Medical application of optical fibers: a detailed review

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.

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

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