**Part 3**

**Medical Device Performance** 

122 Biomedicine

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**6** 

*New Delhi India* 

**Optical Fiber Gratings in Perspective** 

**of Their Applications in Biomedicine** 

**Optical fiber** is a flexible, transparent *waveguide* or "*light pipe*" to transmit light; the latter, in its various forms and facets has caught the attention of humanity since prehistoric times. The ancient civilization used it as fire signals to communicate and later as a therapeutic and preventive tool for better health. In the modern era, the idea that light can be used for communication combined with the phenomenon of total internal reflection, gave rise to the concept of medium for light transmission. As a consequence, by the end of 19th century glass rods as illuminators were realized. Optical fibers were the next step as they are basically glass rods stretched very thin to become long and flexible. Gradual technological advances from 1920s when use of fiber for light transmission was first proposed, to 1980s resulted in glass fibers as the most ideal communication medium for enormous amount of data with lowest possible attenuation. Their inherent properties such as small size (have standard thickness of ~0.250 mm that can be less than that of surgical suture), biocompatibility, non-toxicity, chemical inertness and remote monitoring capability, make them quite lucrative for usage in the biomedical area. These fibers thus have diverse applications ranging from illumination to imaging, from phototherapy to precise surgery, from monitoring complex biomechanical dynamics to wearable smart sensors. In fact, after their first practical application in flexible endoscopes reported by Basil Hirschowitz in 1957 for illuminating and imaging internal organs of human body, the optical fibers have come a long way as sensors for various physiological parameters as well. This book chapter describes a special type of fiber optic tool, called fiber grating, its unique features with reference to potential applications in the field of biomedicine not only as in-fiber devices but

Although glass fibers as endoscope were being used for medical applications since 1950s, they had very limited applications because of their very high power loss (~1000 dB/km) and non availability of a compatible light source. The solution for the second problem came with the first Laser fabrication in 1960 by Maiman that had the potential to be ideal light source

**1. Introduction** 

also as sensing elements. (Mishra, 2011)

**2. History** 

*Central Scientific Instruments Organisation, Chandigarh Council of Scientific and Industrial Research (CSIR),* 

Vandana Mishra and Nahar Singh
