Recently, wavelet transform has been applied widely in watermarking research as its excellent multi-resolution analysis properties. Almost all previous works on watermarking capacity are realized in spatial domain. This paper proposes a new adaptive watermarking capacity analysis method in wavelet domain. This paper also analyzes the relationship between watermarking capacity and watermarking detection bit error rate (BER), and derives the relation between capacity and the limit of BER. According to the result of research, watermarking detection BER is mainly influenced by the watermarking average energy and watermarking capacity. The BER rises with the increase of watermarking capacity.
The performances of SCDCF-based and RDF-based 40Gb/s OTDM and WDM systems are compared by means of numerical simulation. Theory and numerical results were presented and discussed with 40Gb/s signal of different duty cycles. Cross-phase modulation effects in 40Gb/s WDM systems are showed for the first time. We did find that in single channel transmission small duty cycle signal shows superior performance. The problem of RDF based system is mainly due to large nonlinearity of the RDF fiber we choose to calculate. The residual dispersion remains potential problem even at very excellent slope compensation in 40Gb/s systems. RDF based system offers more robust performance than SCDCF at the same value of compensation rate due to its relative short SMF fiber in every span.
In this paper, the effects of walk-off in NOLM-based wavelength conversion is analyzed, as well as group velocity dispersion (GVD) and self-phase modulation (SPM). Fiber Bragg gratings (FBGs) are introduced into the NOLM, serving as narrow bandpass filters. Corresponding coupled mode nonlinear Schroedinger equations (CMNSEs) and equations of the filter transmission window are given. Meanwhile, the optimal parameters of the system. Finally, time-resolved numerical analysis of our scheme is performed. And it reveals that the introduction of FBGs has improved the performance of NOLM-based wavelength conversion.
In this paper, a design method by using comb-like dispersion profiled fiber (CDPF) to achieve pulse compressing has been given, and corresponding numerical model was also presented. Based on this model, the effect of nonlinear phase shift on pulse width and waveform from CDPF compressor was studied under the condition of different pulse peak power. The numerical results reveal that the incident pulse peak power and nonlinear phase shift should be satisfy certain conditions, to get the suited CDPF compressor for the ultrahigh speed OTDM system using.