**5. Conclusion**

We have presented a detail analysis of all-optical DEMUX based on FWM in SOAs by solving the modified nonlinear Schrödinger equation using the FD-BPM. From this analysis, it was clarified that the optimization of the input pump pulsewidth is crucial to achieve a high ON-OFF ratio. We have obtained an optimum input pump pulsewidth of 1 ~ 3 ps for 1 ps, 250 Gbit/s input probe pulses. The shorter limit of the pulsewidth is due to detuning between the pump and probe frequency, which is determined by the gain bandwidth of the SOA. In order to realize faster DEMUX operation, SOAs with broader gain bandwidth are required. We have also simulated pattern effects in the FWM signal. When the number of input probe pulses increases, the FWM signal power decreases, however; the FWM signal waveforms remain unaffected. The peak power fluctuation of the FWM signal can be reduced by using the strong pump pulses and/or weak probe pulses. The energy fluctuation of the FWM signal decreases to less than 1% for a 30-bits, 250-Gbit/s input probe pulse train with a pulse energy of 0.01 pJ. This small fluctuation should not disturb the practical DEMUX operation. We also confirmed the DEMUX from time multiplexed signals by repetitive pump pulses. The strong energy pump pulses decrease the FWM signal intensity, however, there is no pattern effect due to gain saturation, because the pump pulses are injected continuously.

## **6. Acknowledgments**

The authors would like to thank Dr. T. Kawazoe and Mr. Y. Yamayoshi for their helpful contribution to this work.

## **7. References**


We have presented a detail analysis of all-optical DEMUX based on FWM in SOAs by solving the modified nonlinear Schrödinger equation using the FD-BPM. From this analysis, it was clarified that the optimization of the input pump pulsewidth is crucial to achieve a high ON-OFF ratio. We have obtained an optimum input pump pulsewidth of 1 ~ 3 ps for 1 ps, 250 Gbit/s input probe pulses. The shorter limit of the pulsewidth is due to detuning between the pump and probe frequency, which is determined by the gain bandwidth of the SOA. In order to realize faster DEMUX operation, SOAs with broader gain bandwidth are required. We have also simulated pattern effects in the FWM signal. When the number of input probe pulses increases, the FWM signal power decreases, however; the FWM signal waveforms remain unaffected. The peak power fluctuation of the FWM signal can be reduced by using the strong pump pulses and/or weak probe pulses. The energy fluctuation of the FWM signal decreases to less than 1% for a 30-bits, 250-Gbit/s input probe pulse train with a pulse energy of 0.01 pJ. This small fluctuation should not disturb the practical DEMUX operation. We also confirmed the DEMUX from time multiplexed signals by repetitive pump pulses. The strong energy pump pulses decrease the FWM signal intensity, however, there is no pattern effect due to gain saturation, because the pump

The authors would like to thank Dr. T. Kawazoe and Mr. Y. Yamayoshi for their helpful

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**8** 

*Latvia* 

**Realization of HDWDM Transmission System with the Minimum Allowable Channel Interval** 

Nowadays, a skyrocketing growth is observed worldwide in the bit rates of transmitted information, which is associated with development of broadband information transmission types. The annual global internet protocol (IP) traffic will exceed half a Zettabyte in four years. At just under 44 Exabytes per month, the annual run rate of traffic in the late 2012 will be 522 Exabytes per year. Driven by high-definition video and high-speed broadband penetration, the consumer of IP traffic will bolster the overall IP growth rate so that it sustains a steady growth rate through 2012, growing at a compound annual growth rate

(CAGR) of 46 percent (see Fig. 1) [Cisco Systems, 2008].

CAGR 46%

10

20

30

**Petabytes per month**

40

50

Fig. 1. Global IP Traffic Forecast (2006–2012) [Cisco Systems, 2008].

In turn, to provide high-quality transmission it is necessary to develop the next generation optical networks (NGONs) that would transmit properly huge volumes of information. The optical transmission systems from the very outset have been able to offer new possibilities for solving problems of ever increasing urgency that are dictated by the need for frequency bands and transmission speed. Such networks have become one of the most important

<sup>2006</sup> <sup>2007</sup> <sup>2008</sup> <sup>2009</sup> <sup>2010</sup> <sup>2011</sup> <sup>2012</sup> <sup>0</sup>

**Year**

**1. Introduction** 

Jurgis Porins, Vjaceslavs Bobrovs and Girts Ivanovs *Riga Technical University, Institute of Telecommunications* 

semiconductor optical amplifier. *IEEE Photon. Technol. Lett.,* vol. 10, pp. 890-892, ISSN 1041-1135.

