Fundamentals of Plastic Optical Fibers

2Transmission Loss

It would not be an exaggeration to say that the history of plastic optical fibers (POFs) has been a history of the attempts to reduce their transmission loss. The transmission loss limits how far a signal can propagate in the fiber before the optical power becomes too weak to be detected. It measures the amount of light lost between the input and output; it is normally expressed in decibels and defined as

2.1

This is the sum of all the losses. The various mechanisms contributing to the losses in POFs are essentially similar to those for glass optical fibers (GOFs), but the relative magnitudes are different. Figure 2.1 shows the loss factors for POFs, which are divided into intrinsic and extrinsic factors. Although extrinsic factors such as contaminants or waveguide imperfections can sometimes cause important losses, once an optimum fabrication process has been achieved, they can be ignored. The intrinsic factors are further classified into absorption and scattering losses. This chapter is devoted to a discussion of these influences in POFs and how the transmission loss has been reduced.

Figure 2.1 Classification of intrinsic and extrinsic factors affecting POF attenuation.

2.1 Absorption Loss

2.1.1 Electronic Transition Absorption

The absorption of light ...