Bend loss

If tlie guides are lossless (here we ignore bending losses) and we only launch a field into guide 1 (i.e. = 1, 2 =... 

The correclion (Fig- 6-14rZ) accounts for the extra losses due to developing flow in the outlet tangent of the pipe, of length L. The total loss ror the bend plus outlet pipe includes the bend loss K plus the straight pipe frictional loss in the outlet pipe 4fL /D. Note that = 1 for L /D greater than the termination of the curves on Fig. 6-14d, which indicate the distance at which fully developed flow in the outlet pipe is reached. Finally, the roughness correction is... 

For sensing applications, high bending losses restrict the applicability as (flexible) light pipes. Practical applications are mostly restricted to gas cells, where the hollow waveguide acts as a compact multi-reflection cell to increase the sensitivity in comparison to single-pass cells. 

Veldhuis G.J., VandeVeen L.E.W., Lambeck P.V., Integrated optical refractometer based on waveguide bend loss, J. Lightwave Technol. 1999 17 857. 

Sorensen, T. Broeng, J., Bjarklev, A. et ah. Macro-bending loss properties of photonic crystal fibre. Electron. Lett., 37, 287, 2001. 

A hollow-optical fiber is a prospective fiber-optic probe for infrared spectroscopy in medicine, owing to its nontoxicity and high mechanical and chemical stability [5]. However, it has been difficult to use it for remote spectroscopy because of its relatively high bending losses. Accordingly, the transmission efficiency should be improved by optimizing the fabrication conditions. 

The lines are the Lorentzian fits to the measured data. The quality factor (Q) of the 10 pm microring is 1515, which is larger than that of the 5 pm microring (0)860 due to a smaller bending loss. Free spectral range FSR) and the full width half maximum of the resonance peak (Ak) are also shown in (c, d) (From [4])... 

FIGURE 6.15 The variation of free spectral range (FSR), the distance between resonant modes, and ring radius with the index of refraction difference between the core and the cladding is shown. As ring radius decreases, optical loss increases and acceptable ring radius sizes are normally chosen to represent the point where bending loss becomes comparable to other sources of optical loss. 

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