Design of tunable erbium doped fiber ring laser for optical fiber based broadband applications

Tunable erbium doped fiber ring lasers (EDFRL) play an important role in wavelength division multiplexing (WDM) telecommunication systems, testing and characterization of components in these systems and optical fiber sensor applications. In this thesis firstly, design, theoretical analysis and experimental characterization of conventional EDFRL have been performed. The effects of erbium doped fiber (EDF) length, output coupler ratio, erbium doping concentration and pump power on its performance have been analyzed both theoretically and experimentally and it has been seen that the results are in good quantitative agreement. With the optimum parameters a high output power level (∼+4.5 dBm), a wide wavelength tuning range (∼80 nm) covering C+L bands and a high optical signal-noise ratio (OSNR) (54.7 dB) have been achieved. Also, in this study, two novel EDFRL configurations based on loop erbium doped fiber amplifier (EDFA) design and double-pass EDFA design have been proposed. Output power and spectral performances of both EDFRL designs have been analyzed experimentally. A tuning range over 70 nm covering C+L bands, a moderate output power of -3.2 dBm and a high OSNR value of 59 dB have been obtained with both novel EDFRL configurations. Also, narrow linewidths (<17 pm) with few spectral modes have been achieved for all three EDFRL designs. In the last part of the study, the performance of EDFRLs in WDM communication and sensor applications have been examined and found to be suitable for use in critical applications. As a result, it has been understood that, the designed tunable EDFRLs can be used with high performance in broadband fiber optic applications due to their stable output powers, wide tuning ranges, high OSNR values and narrow linewidths.