| Abstrakt: |
Semiconductors have large optical nonlinearity with response speed in the several tens of picosecond range, making them ideal use as all-optical regenerators and wavelength converters. We theoretically and experimentally investigated optical nonlinearities induced by carrier dynamics both in forward biased semiconductor waveguide (SOA) and in reverse biased semiconductor waveguide (EAM). We made a detailed theoretical study of carrier dynamics in semiconductor waveguides by using the newly developed time-dependent transfer matrix method. To confirm the simulation results, we propose utilizing a polarization discriminating delayed interferometer (PD-DI) configuration as a simple technique for measuring optical nonlinearities such as cross gain modulation (XGM), cross absorption modulation (XAM), and cross phase modulation (XPM). In the first part of the paper, we reviewed SOA-based regenerators. As expected from the simulation results, we confirmed that injection of the transparent assist light was very effective in reducing of the SOA gain recovery time of down to a few tens of picoseconds. We further demonstrated 40 Gbit/s regeneration using an SOA-one-arm MZI (so-called UNI) configuration. The superior regeneration capability of two-stage UNI was successfully confirmed by a recirculating loop experiment up to 30,000 km with 150 regenerations. In the latter part of the paper, we reviewed all-optical regenerators using EAM. A bit-synchronized rf-driven XAM 3R regenerator consisting of only one EAM for both gating and timing correction was demonstrated at 20 Gbit/s. An EAM in conjunction with delayed interferometer configuration, which utilizes XPM as well as XAM in the EAM, has structurral simplicity and fast regeneration operability up to 100 Gbit/s. The fast response of EAM allows the optical regeneration with a small pattern word effect. [ABSTRACT FROM AUTHOR] |
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