Investigation of EDFA power transients in circuit-switched and packet-switched optical networks

Doctoral thesis English OPEN
Muhyaldin, Siham

Erbium-doped fibre amplifiers (EDFA’s) are a key technology for the design of all optical communication systems and networks. The superiority of EDFAs lies in their negligible intermodulation distortion across high speed multichannel signals, low intrinsic losses, slow gain dynamics, and gain in a wide range of optical wavelengths. Due to long lifetime in excited states, EDFAs do not oppose the effect of cross-gain saturation. The time characteristics of the gain saturation and recovery effects are between a few hundred microseconds and 10 milliseconds. However, in wavelength division multiplexed (WDM) optical networks with EDFAs, the number of channels traversing an EDFA can change due to the faulty link of the network or the system reconfiguration. It has been found that, due to the variation in channel number in the EDFAs chain, the output system powers of surviving channels can change in a very short time. Thus, the power transient is one of the problems deteriorating system performance. In this thesis, the transient phenomenon in wavelength routed WDM optical networks with EDFA chains was investigated. The task was performed using different input signal powers for circuit switched networks. A simulator for the EDFA gain dynamicmodel was developed to compute the magnitude and speed of the power transients in the non-self-saturated EDFA both single and chained. The dynamic model of the self-saturated EDFAs chain and its simulator were also developed to compute the magnitude and speed of the power transients and the Optical signal-to-noise ratio (OSNR). We found that the OSNR transient magnitude and speed are a function of both the output power transient and the number of EDFAs in the chain. The OSNR value predicts the level of the quality of service in the related network. It was found that the power transients for both self-saturated and non-self-saturated EDFAs are close in magnitude in the case of gain saturated EDFAs networks. Moreover, the cross-gain saturation also degrades the performance of the packet switching networks due to varying traffic characteristics. The magnitude and the speed of output power transients increase along the EDFAs chain. An investigation was done on the asynchronous transfer mode (ATM) or the WDM Internet protocol (WDM-IP) traffic networks using different traffic patterns based on the Pareto and Poisson distribution. The simulator is used to examine the amount and speed of the power transients in Pareto and Poisson distributed traffic at different bit rates, with specific focus on 2.5 Gb/s. It was found from numerical and statistical analysis that the power swing increases if the time interval of theburst-ON/burst-OFF is long in the packet bursts. This is because the gain dynamics is fast during strong signal pulse or with long duration pulses, which is due to the stimulatedemission avalanche depletion of the excited ions. Thus, an increase in output power levelcould lead to error burst which affects the system performance.
  • References (93)
    93 references, page 1 of 10

    2 Gain dynamic model of the EDFA 64 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 2.2 Erbium-doped fibre amplifier basics . . . . . . . . . . . . . . . . . . . . . 65 2.3 Gain dynamics model of single EDFA . . . . . . . . . . . . . . . . . . . . 71 2.4 EDFA dynamics model for OSNR investigation . . . . . . . . . . . . . . . 73 2.5 Properties of EDFAs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 2.6 Pump configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 2.7 Fibre lengths and geometries . . . . . . . . . . . . . . . . . . . . . . . . . 86 2.8 EDFA effects on the dynamic phenomena in optical networks . . . . . . . . 88 2.9 Numerical simulation techniques . . . . . . . . . . . . . . . . . . . . . . . 91 2.10 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

    4 Effect of Poisson traffic on EDFA transients 133 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 4.2 Traffic types and models . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 4.2.1 Poisson distribution traffic model . . . . . . . . . . . . . . . . . . 134 4.3 Impact of the Poisson traffic on the power transients of the EDFA . . . . . . 136 4.3.1 Simulation parameters . . . . . . . . . . . . . . . . . . . . . . . . 136 4.3.2 Results and analysis . . . . . . . . . . . . . . . . . . . . . . . . . 137 4.3.2.1 Power transient numerical analysis . . . . . . . . . . . . 138 4.3.2.2 Power transient statistical analysis . . . . . . . . . . . . 140 4.4 Power transients at small signal power . . . . . . . . . . . . . . . . . . . . 145 4.4.1 Simulation parameters . . . . . . . . . . . . . . . . . . . . . . . . 145 4.4.2 Results and analysis . . . . . . . . . . . . . . . . . . . . . . . . . 145 4.4.2.1 Numerical analysis of the power transients . . . . . . . . 146 4.4.2.2 Statistical analysis of power transients . . . . . . . . . . 148 4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

    6 Effect of power transients on optical receiver 196 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 6.2 Investigation of power and OSNR transients in cascades of EDFAs for optical networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 6.2.1 Analysis of OSNR transients in EDFAs chain . . . . . . . . . . . . 199 6.2.2 Effect of power and OSNR transients of cascaded EDFAs on the optical receiver for WDM networks . . . . . . . . . . . . . . . . . 205 6.2.3 Effect of the abrupt input power on the power and OSNR transients in the EDFAs chain . . . . . . . . . . . . . . . . . . . . . . . . . . 207 6.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

    7 Gain Locking System for EDFA in WDM Optical Networks 212 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 7.2 PID controller for the EDFA . . . . . . . . . . . . . . . . . . . . . . . . . 213 7.3 Simulation parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 7.4 Numerical simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 7.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

    8 Conclusions and future work 238 8.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 8.2 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 B Appendix 265 B.1 Basic model parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 B.1.1 Absorption and emission cross sections . . . . . . . . . . . . . . . 265 B.1.2 Amplified spontaneous emission(ASE) . . . . . . . . . . . . . . . 266 B.1.3 Overlap factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 B.1.4 Lifetimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 B.1.5 Line-width and broadening . . . . . . . . . . . . . . . . . . . . . . 267 B.2 Gain model of EDFA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 B.3 Gain dynamic model of EDFA . . . . . . . . . . . . . . . . . . . . . . . . 268 B.4 1 dB increase-time/decrease-time of OSNR . . . . . . . . . . . . . . . . . 271 [84] A. Bahrampoura, M. Mahjoeib, and A. Rasoulib, “A theoretical analysis of the effects of erbium ion pair on the dynamics of an optical gain stabilized fiber amplifier ,” Optics Communications, vol. 265, pp. 283-300, September 2006.

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