Coherent Population Oscillations Induced Slow Light For WDM Systems

In the current optical communication systems, optical signals have to be converted into electrical signals for the data storage and routing. This will introduce the so called electrical bottleneck for the data rate. Optical buffering, which can largely increase the data rate, may be achieved by making use of the controllability of light speed. The slow light becomes one of the key technologies for all-optical communications.This paper presents slow light induced by CPO effect for WDM systems, analyzes the theory of CPO and introduces some key parameters such as relative modulation attenuation, group refractive index, delay, bandwidth and delay-bandwidth product of slow light based on CPO.Then,we demonstate the results with some figures made by Matlab and summarize the characteristics of slow light. Finally this paper discuses light transmission in the media with the Gaussian pulse analysis for the study of light transmission in the media.All of the present experiments and theories of the slow light based upon the CPO effect deal with the resonant situation where the pump frequency exactly matches the gap of the energy levels of active atoms. However, in a WDM system, there exist many channels with subsequent wavelengths. Unless taking wavelength conversion one channel by one channel, otherwise only one channel wavelength within all the channels matches the resonant condition and all the other channels work in the off-resonant region. Since it is costly and not necessary to convert all off-resonant wavelengths to be resonant, it is necessary to understand both the resonant and off-resonant situations. In this work, the CPO theory of slow light is extended to cover both resonance and off-resonance. At last, we discuss the bandwidth of slow light and simulate delay and bandwidth, and with delay-bandwidth product corresponding to each WDM wavelength. When the probe light is not resonant with the system, the bandwidth may be increased.