Question 3 (Total Marks: 15 marks) As a longhaul optical engineer, you have been assigned to investigate the impact of e

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Question 3 Total Marks 15 Marks As A Longhaul Optical Engineer You Have Been Assigned To Investigate The Impact Of E 1 (464.35 KiB) Viewed 40 times

Question 3 (Total Marks: 15 marks) As a longhaul optical engineer, you have been assigned to investigate the impact of erbium- doped fibre amplifiers (EDFAs) on the optical signal-to-noise ratio of long haul signal transmission. Shown in Fig. 5 is the experiment setup you have used to carry out this study. The EDFA is placed at the receiver (Rx) and located 200 km away from the transmitter (Tx). The following parameters are used in the set up: ● ● Single mode fibre with ● O Fibre attenuation of 0.2 dB/km • Wavelength = 1550 nm Bit rate 10 Gb/s O Fibre dispersion is negligible and can be ignored Transmission power at Tx is 0dBm Optical bandwidth = 100 GHz Minimum power required at the Rx = 0 dBm EDFAs are used to provide exact amount of gain to compensate for the fibre losses and ensuring minimum power requirement is met at the Rx Amplified spontaneous emission noise (ASE) is the only noise source in the link nsp = 1.5 PASE - nsp (G Pave OSNR= PASE Total ASE noise = Tx = hc -1)Bopt N 1 PASE- where N = number of EDFAs in the link 200 km Fig. 5 Rx a. With the given information, calculate the optical signal-to-noise ratio (OSNR) at the receiver in dB. (3 marks)
b. To understand the impact of multiple EDFAs in the link, the experiment is redesigned to include a second EDFA at the 100 km point in the link as shown in Fig. 6. In this layout, both the EDFAs are assumed to be identical with an nsp = 1.5, and are designed to compensate the length of the fibre immediately before them (i.e. each EDFA compensates for the 100 km of fibre before it). Calculate the OSNR in dB at the receiver for this layout. (3 marks) Tx Tx 100 km (0) 50 km Fig. 6 c. You further reduce the distance between the EDFAs with a new configuration as shown in Fig. 7. In this configuration, all EDFAs are identical with nsp = 1.5, and are designed to compensate the length of the fibre immediately before them. Calculate the OSNR in dB at the receiver for this layout. (3 marks) 50 km B 100 km 50 km Fig. 7 50 km Rx D Rx d. By comparing the results in a-c, what conclusion can you made with regards to the relationship between the distance between the EDFAs and the OSNR at the receiver? And why is it so? (2 marks) e. Briefly discuss the disadvantages of reducing the distance between the optical amplifiers in a longhaul optical link. (2 marks) f. With reference to Fig. 7, identify which of the amplifiers are in-line amplifiers and which would be pre-amplifiers. Briefly describe the differences between these two types of amplifiers. (2 marks)