Absorption coefficient optical fibers

The Kubelka-Munk theory of diffuse reflectance is a good description of the optical properties of paper. The two parameters of the theory, absorption and scattering coefficient, are purely phenomenological, but are closely related to basic properties of paper. The absorption coefficient is approximately a linear function of the chrcmgphore concentration in the paper. The scattering coefficient is related to the nonbonded fiber surface area in the paper, or the area "not in optical contact," and the Fresnel reflectivity of that surface. 

As a result of the nature of the photon emission there is no preference for a certain angle. However, the presence of local obstructions and absorption variations of the sample will have an influence on the distribution. Moreover the local variation of the specimen surface (topography)may result in variation of the internal reflection coefficient, and this reduces the efficiency for the light to get out of the specimen (analogous to light in an optical fiber)and induces local polarization of the light. 

Attenuation The combination of optical energy losses from a light pulse traversing a length of optical fiber resulting from absorption and scattering, typically referred to as intrinsic attenuation, and bending losses, typically referred to as extrinsic attenuation, expressed in dB. However, attenuation is often used as a synonym for attenuation coefficient, expressed in dB/km. 

An absorption coefficient as small as 0.001 cm is thus equivalent to an optical loss rate of 434.3 dB/km, which is extremely high from a long-distance communication point of view. (See Sec. 6.7, Optical Communications Fiber .)... 

We have briefly considered some of the applications of semiconductor alloys in Chapter 3. In current technology the use of alloys is seen in heterojunction bipolar transistors, laser diodes, and numerous other devices. Laser diodes used in fiber-optic communications, for example, are required to operate at a high modulation rate and at very specific wavelengths where the absorption coefficient in the fiber is unusually low. Thus, it is critical to these devices to know how to control the energy gap of the semiconductor effectively. Alloying is also necessary for improvement of laser efficiencies, which helps to allow the device to operate in a continuous mode. 

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