Fiber optic sensors detect sleep apnea syndrome

FBG sensors for sleep apnea detectionSleep apnea syndrome is regarded as a risk factor for traffic accidents because it leads to excessive daytime sleepiness. A fiber optic sensor based on optical fibers for sleep apnea syndrome has been tested in a clinical application varying in age from 13 to 78 years. Such a fiber sensor is perfect for preliminary sleep apnea syndrome screening because its respiratory disturbance index corresponds well with the apnea-hypopnea index.

The promising application of such fiber optic sensors includes a screening of patients suffered from the SAS during standard sleep at home. Moreover, the process of downsizing the optical fiber sensors results in the connection between PSG and pulse oximetry. The fiber sensor can be used to examine sleep apnea syndrome in children (2 – 12 years) providing improved pediatric analysis.

It should be noted that the novel fiber optic technology provides more accurate SAS results compared to the traditional sensing system. Additionally, the developed optical fiber sensor is considered to be non-invasive and non-restrictive, also it is quiet and compact, therefore, it is highly useful for the process of SAS screening during conventional sleep at home.

Fiber optic sensors provide a promising application for screening latent patients who suffered from sleep apnea syndrome during normal sleep. Optical fibers in such sensing systems are narrower and wider within several centimeters. Researchers use commercially affordable optical fibers for SAS screening. The operating principle of fiber sensors is based on the measurement of the deviation of output optical power from an optical fiber sheet by micro-bending loss and/or bending loss.

Significant benefits of fiber optic sensing systems include no need for a patient to use any specific clothing or devices because the measurement results are transmitted to a remote place for further analysis and diagnosis. “The deviation in the output optical fiber power from the POF sheet due to micro-bending loss and/or bending loss caused by the lateral pressure change created by the motion of the person’s chest during respiration is measured.”

Also, the researchers have designed a multi-channel fiber optic sensor and applied it in a hotel, full medical check-up, and clinical test in pediatrics. The fiber optic sensing system demonstrated 38/42 42 examinees had  Pro-AHI > 5 and were suspected of sleep apnea syndrome. The fiber sensor has a compact size by it having only 15.3% of the volume of a standard sensing system that allows detecting sleep apnea syndrome. The obtained results show that the fiber optic system is perfect for preliminary SAS screening and monitoring of the respiration and heartbeat of neonates. 

Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for clients. Optromix produces a wide range of fiber optic devices, including cutting-edge customized fiber optic Bragg grating product line and fiber Bragg grating sensor systems. Moreover, Optromix is a top choice among the manufacturers of fiber Bragg grating monitoring systems. If you have any questions, please contact us at info@optromix.com

Devices based on fiber optic technology

Optical fibers are flexible waveguides of the optical range. Usually made of some kind of glass, they can potentially be very long (achieving hundreds of kilometers). Quartz glass is most often used for the manufacture of optical fibers because of its unique properties, in particular:

  • extremely low energy losses of radiation propagating in it (realized only in ultra-pure material);
  • surprisingly high mechanical tensile and bending strength.

Most optical fibers used in laser optics have a core with a refractive index slightly higher than that of the outer layer (the so-called shell).  Light introduced into the optical fiber is distributed mainly in the region of its core, although some of the radiation can also penetrate into the shell. Light is retained in the fiber due to the effect of full internal reflection at the border of regions with different refractive index, or due to the gradient of the refractive index in the core of the optical fiber. 

They less commonly use fibers that implement a different principle of light retention in them. Such optical fibers are based on the fiber Bragg grating structures and photonic crystals to form a photonic stop-band. This technique is fundamentally different from the method of retaining light in conventional fibers.

To be more precise, a fiber Bragg grating is a periodic or aperiodic perturbation of the effective refractive index in the fiber core. As a rule, the Bragg grating has a length of about a few millimeters or centimeters. The width of the reflection band of the fiber Bragg grating, which is usually much less than 1 nm, depends on both the length of the Bragg grating and the depth of the refractive index modulation. Narrow-band gratings required, for example, for the manufacture of single-frequency fiber lasers or for certain optical filters can be obtained using long gratings with weak modulation. Wide reflection bands can be obtained on short Bragg gratings with deep modulation, but also on gratings with aperiodic modulation.

Since the maximum reflection wavelength depends not only on the Bragg grating period but also on temperature and mechanical stresses, fiber Bragg gratings can be used in temperature and stress sensors. Transverse stresses compress the optical fibers of gratings between two flat plates, inducing birefringence and thus causing the Bragg wavelength to depend on polarization.

Additionally, fiber Bragg gratings are often used for the development of fiber optic sensors. Fiber optic sensors are fiber optic systems for detecting certain factors, usually temperature or mechanical stress, but sometimes also displacement, vibration, pressure, acceleration, rotation, and chemical concentrations. 

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com