Biophotonics_Concepts_to_Applications

end (the light exit end) of thefiber have been proposed and demonstrated by using a
fusing and polishing technique [ 27 ].

Example 3.11The bore diameters in coated hollow-corefibers can range

from 50 to 1200μm. In thesefibers the loss varies as 1/r^3 , where r is the bore

radius. Compare the losses of 300-μm and 800-μm hollow-corefibers relative

to a 1200-μm bore sizedfiber.

Solution: First, assume that the loss is 0.2 dB/m for afiber with a bore size

rref= 1200-μm.

(a) Then for a 300-μm hollow-corefiber the loss is

Loss at 300lm¼ðÞð 0 :2dB=m rref=rÞ^3 ¼ðÞð 0 :2dB=m 1200 = 300 Þ^3

¼ 12 :8dB=m

(b) For an 800-μm hollow-corefiber the loss is

Loss at 800lm¼ðÞð 0 :2dB=m rref=rÞ^3 ¼ðÞð 0 :2dB=m 1200 = 800 Þ^3

¼ 0 :68 dB=m

3.9 Photonic Crystal Fibers.

Aphotonic crystalfiber(PCF) has a geometric arrangement of internal air holes
that run along the entire length of thefiber [ 30 – 35 ]. A PCF also is referred to as a
microstructuredfiberor aholeyfiber. The core of the PCF can be solid or hollow as
shown in Fig.3.13by the cross-sectional images of two typical PCF structures [ 5 ].

Fig. 3.13 Sample structural arrangements of air holes in solid-core (left) and hollow-core (right)
PCF (J. Biomed. Opt. 19(8), 080902 (Aug 28, 2014). doi:10.1117/1.JBO.19.8.080902)

78 3 Optical Fibers for Biophotonics Applications