Biophotonics_Concepts_to_Applications

When usingfiber bundles, there is a trade-off between light collection efficiency
and good image resolution [ 5 ]. A large core diameter enables high light trans-
mission but poor image resolution. A thicker cladding avoids crosstalk among
individualfibers but limits light collection and image resolution, because more of
the light-emitting area is blocked when a thicker cladding is used. In practice, the
core diameter of individualfibers is 10– 20 μm and the cladding thickness is around
1.5–2.5μm. Coherentfiber bundles are the key components in a variety offiber
optic endoscopes. Current sophisticated ear, nose, throat, and urological procedures
utilize high-resolutionflexible image bundles for image transfer.

3.14 Summary

The extensive and rapidly growing use of photonics technology for basic life
sciences research and for biomedical diagnosis, therapy, imaging, and surgery has
been assisted greatly through the use of a wide variety of opticalfibers. Table3.1
gives a summary of variousfibers. The biophotonics applications of thesefibers
include

• Light care: healthcare monitoring; laser surfacing or photorejuvenation


• Light diagnosis: biosensing, endoscopy, imaging, microscopy, spectroscopy


• Light therapy: ablation, photobiomodulation, dentistry, laser surgery, oncology
  Major challenges in biophotonics applications to the life sciences include


• How to collect emitted low-power light (down to the nW range) from a tissue
  specimen and transmit it to a photon detector

Randomly oriented

optical fibers

(a) (b)

Collection

fibers

Illuminating

fiber

Fig. 3.15 aRandomly arrangedfibers in a bundle containing manyfibers;bCoherent bundle
cable with identical arrangements offibers on both ends (J. Biomed. Opt. 19(8), 080902 (Aug 28,
2014). doi:10.1117/1.JBO.19.8.080902)

84 3 Optical Fibers for Biophotonics Applications