Design Of All-Optical Regeneration Integrated Chips And Their Performance Test

With the development of optical switching integrated chip technology, all-optical regeneration integrated chips start to gain people’s attention. This thesis investigates the realization of optical amplification and optical re-shaping functions on silicon chips through the third-order parametric process, as well as multi-level optical regeneration. The main contents and innovations are listed as follows:1. The nonlinear transmission characteristics of guided optical waves in silicon waveguides are investigated and the parametric amplification performance of silicon waveguides is characterized by the on-off gain. We analyze the effect of two-photon absorption and free carrier absorption on the on-off gain. The calculation results show that, the on-off gain of parametric amplification can be effectively improved by optimizing the cross section size and the length of silicon waveguides. By using the two-photon absorption effect, a quasi-step-like power transfer function can be realized, and the re-shaping and amplitude-limiting performance can further be optimized by changing the length of silicon waveguides or reducing free carrier absorption.2. We designed and fabricated the silicon-based all-optical 2R (re-amplifying and re-shaping) regeneration chips with three different lengths of lcm,2cm, and 3cm, which have the same cross section of 606nmx 220nm. Our experimental results show that, the linear loss of silicon waveguides is 2.2dB/cm, and the coupling loss of single grating is 6dB. The phenomena of two-photon absorption and free carrier absorption are also clearly observed in the experiment. The power transfer functions (PTFs) of the 3cm-long regeneration chip in data-pump scheme are measured at different wavelength intervals. The PTF slope of around 1.8 and a 3.9dB extinction ratio improvement for 12.5Gbit/s NRZ (non-return-to-zero) signal are experimentally achieved in the regeneration experiment.3. We propose a universal design method for all-optical multi-level regenerators and take advantage of the normalized power transfer function (PTF) for analyzing the re-shaping performance by the noise reduction ratio. The amplitude and phase conditions in the first-order approximation to the ideal step-like PTF are given for Mach-Zehnder interferometer (MZI)-based regenerators. As an example, we describe the design process of the MZI-based optical regenerator constructed by a section of nonlinear fiber and an optical phase shifter. It is shown that, the parameter of reference power level (RPL) can be regarded as the upper limit of input power, which is useful for the measure of the multi-level regeneration performance. The number of regenerative power levels increases with the RPL parameter. For 4-levels pulse amplitude modulated (4PAM) optical signals degraded by the Gaussian noises, with the input amplitude standard deviation 0.02, the resulting MZI-based all-optical regenerator has an average noise reduction ratio (NRR) of 6.5dB, better than that in the first-order approximation by about 5dB.