We present results from theoretical analysis of the phase dynamics in semiconductor optical amplifiers(SOAs).In particular,we focus on an aspect of the ultra-fast phase recovery that currently does not have adequate in-depth theoretical analysis and clear explanation of the physical mechanism.We build up a numerical model to analyze the ultra-fast phase recovery of semiconductor optical amplifiers in details.To investigate the phase response characteristics,we analyze the different contributions to the phase shift,including intra-band effects such as carrier heating,spectral hole burning,and inter-band effects such as carrier depletion.In addition,the impact of the pulses energy on phase shift is also investigated.Based on the analysis of phase response characteristics,we further explain the reason why a delay occurs between gain response and phase response.The analysis results are in good agreement with the reported experimental results.The results presented in this paper are useful for the SOA-based ultra-fast optical signal processing,such as optical switches,optical logic gates,and optical Add/Drop multiplexer.
A novel method for characterizing the nonlinearity of all-optical sampling is proposed based on the normalized transfer function.Simulation results demonstrate the effectiveness of our method.Furthermore,an all-optical sampling experiment is performed to verify our method.Both simulation and experiment show consistency between our method and the measurements.The method only requires normalization and polynomial fitting of the transfer curve,and enables direct expression of the nonlinearity with the coefficients of the normalized transfer function.
ZHANG ShangJian LIN ChangYu LI Xuan ZOU ZhiTai LIU Yong LIU YongZhi
We propose a new method for characterizing optical phase modulators based on phase modulation-to-intensity modulation (PM-to-IM) conversion in dispersive fibers.The fiber dispersion spectrally alters the relative phasing of the phase-modulated signal and leads to the PM-to-IM conversion,which is extended to measure the modulation efficiency of optical phase modulators.In the demonstration,the frequency-dependent modulation index and half-wave voltage are experimentally measured for a commercial phase modulator.Compared with conventional methods,the proposed method works without the restriction of small-signal operations,and allows swept-frequency measurement with high resolution and accuracy by using a vector network analyzer.
