Fiber Optic Tutorials
Electronic Dispersion Compensation
Although electronic dispersion compensation attracted attention as early as 1990 because of its potential low cost and ease of implementation in the form of a integrated-circuit chip within the receiver, it was only after 2000 that it advanced enough to become usable in real lightwave systems. The main limitation of electronic techniques is related to the speed of electronic circuits. Recent advances in digital signal processing (DSP) have made electronic compensation a practical tool not only for GVD but also for PMD.
Dispersion Compensation for High Bit Rate WDM Channels
Commercial WDM systems in which individual channels operate at a bit rate of 40 Gb/s became available by 2002, and efforts were underway to increase the channel bit rate to 100 Gb/s and beyond. For such high-speed systems, the management of channel dispersion poses additional problems. In this tutorial, we focus on several relevant issues.
Dispersion Compensation with Optical Phase Conjugation (OPC)
Although the use of optical phase conjugation (OPC) for dispersion compensation was proposed in 1979, it was only in 1993 that the OPC technique was first implemented experimentally. It has attracted considerable attention since then. In contrast to other optical schemes discussed in previous tutorials, the OPC is a nonlinear optical technique. This tutorial describes the principle behind it and discusses its implementation in practical lightwave systems.
Dispersion Compensation with Dispersion-Equalizing Filters
Fiber gratings constitute an example a whole class of optical filters that can be employed for compensating dispersion in long-haul systems. In this tutorial, we consider several other dispersion-equalizing filters that may be made using fibers or planar waveguides. Such a compact optical filter can be combined with an amplifier module such that both the loss and the dispersion of optical fibers are compensated simultaneously in a periodic fashion. Moreover, an optical filter can also reduce the amplifier noise if its bandwidth is much smaller than the amplifier bandwidth.
Dispersion Compensation with Fiber Bragg Gratings
The dispersion-compensating fibers (DCFs) discussed in the previous tutorial suffer from high insertion losses because of their relatively long lengths. They also enhance the impact of nonlinear effects within a long-haul system. Both of these issues can be resolved to a large extent by using fiber-based Bragg gratings for dispersion compensation.