Analysis Of Linear Optical Amplifiers Based On Cross-Gain Modulation

In the field of wavelength division multiplexing (WDM) of optical communication, with the problems of the network block and the shortage of frequency resource, all optical wavelength conversion (AOWC) have been concerned about. Amplifier is the key device in the wavelength conversion. Recently, a new kind of amplifier was presented, that is the linear optical amplifier (LOA) . LOA has good gain clamping effect, it not only used in WDM system, but also uses XGM in the wavelength conversion, which achieving higher capacity and rate information processing than traditional semiconductor optical amplifier (SOA) .In this paper, the LOA was studied on its basic characteristics and as a wavelength converter. Firstly, a theoretical model of LOA is given, and carrier and photon numbers are analysis numerically using small signal analysis et al. Secondly, a new method of cross-gain modulation based on LOA is presented to study the influences of LOA pump and probe light parameters on extinction ratio characteristics of converted signals. Besides, the elements and excellences of wavelength conversion based on LOA is also discussed. Finally, the basic transmission equation is solved numerically, in order to represent the superiority of LOA, the transmission characteristics of optical pulse as well as the influences of the pulse width on carrier density, carrier lifetime and gain are investigated in detail, and the results is also compared with that of SOA.The results show that, owing to the existence of vertical-cavity laser (VCL) , when the power of input signal is small, the carriers only fluctuated in certain spectrum, and the signal switching has small influence on gain fluctuation, so it performs well with effective crosstalk suppression. When the power of input signal is large, the VCL accelerates the comeback of carriers and thus solves the limits of gain recovery time in traditional amplifiers, which is useful for high speed signal process. Since the VCL of LOA clamps the gain, the gain is insensitive to small signal distortions. Higher pump power, lower probe power and suitable wavelength spans, which between pump and probe, have the advantages to achieve the higher output extinction ratio and conversion efficiency. In the XGM, different compages of pump signal power, probe signal power and input pulse wavelength have direct influence on size of output pulse peak power and pulse shapes. Input pulse width also has influence on gain fluctuation, carrier density, carrier lifetime, but smaller than SOA. Moreover, the wider pulse can cause the smaller influence. It is also proved that the capability of LOA is more excellent than SOA, when they are used as a nonlinear element.