tailieunhanh - Optical Networks: A Practical Perspective - Part 27

Optical Networks: A Practical Perspective - Part 27. This book describes a revolution within a revolution, the opening up of the capacity of the now-familiar optical fiber to carry more messages, handle a wider variety of transmission types, and provide improved reliabilities and ease of use. In many places where fiber has been installed simply as a better form of copper, even the gigabit capacities that result have not proved adequate to keep up with the demand. The inborn human voracity for more and more bandwidth, plus the growing realization that there are other flexibilities to be had by imaginative use of the fiber, have led people. | 230 Components Drop Add Figure A four-channel add drop multiplexer architecture. AOTF Can an AOTF be used to achieve the same level of crosstalk suppression This problem compares different simple add drop multiplexer architectures. a First consider the fiber Bragg grating-based add drop element shown in Figure b . Suppose a 5 tap is used to couple the added signal into the output and the grating induces a loss of dB for the transmitted signals and no loss for the reflected signal. Assume that the circulator has a loss of 1 dB per pass. Carefully compute the loss seen by a channel that is dropped a channel that is added and a channel that is passed through the device. Suppose the input power per channel is -15 dBm. At what power should the add channel be transmitted so that the powers on all the channels at the output are the same b Suppose you had to realize an add drop multiplexer that drops and adds four wavelengths. One possible way to do this is to cascade four add drop elements of the type shown in Figure in series. In this case compute the best-case and worst-case loss seen by a channel that is dropped a channel that is added and a channel that is passed through the device. c Another way to realize a four-channel add drop multiplexer is shown in Figure . Repeat the preceding exercise for this architecture. Assume that the losses are as shown in the figure. Which of the two would you prefer from a loss perspective Problems 231 d Assume that fiber gratings cost 500 each circulators 3000 each filters 1000 each and splitters combiners and couplers 100 each. Which of the two preceding architectures would you prefer from a cost point of view In a photodetector why don t the conduction band electrons absorb the incident photons Consider an ED FA that is required to amplify wavelengths between 1532 nm and 1550 nm within the C-band separated by 100 GHz . a Draw a schematic of this basic ED FA and assume the pump laser is selected