Analysis and Design of Transimpedance Amplifiers for Optical Receivers

Chapter 2Optical Fibers

In the following, we introduce the communication channel presented by the optical fiber. We briefly describe the loss, various forms of dispersion, and nonlinearities of the fiber. For each effect, we discuss what can be done to counteract it in the optical as well as the electrical domain.

2.1 Loss and Bandwidth

Loss

As the optical signal propagates through a long stretch of fiber, it becomes attenuated because of scattering, absorption by material impurities, and other effects. The attenuation is measured in dBs ( of power ratio) and is proportional to the length of the fiber. Fiber attenuation or fiber loss therefore is specified in .

As shown in Fig. 2.1, silica glass has two low-loss windows, one around the wavelength and one around , both of which are used for optical fiber communication. The popular single-mode fiber has a loss of 0.18 to at the 1.55- wavelength and 0.32 to at the 1.3- wavelength. Because the loss is lower at , this wavelength is preferred ...