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Photonic reservoir computing is a new paradigm for performing high-speed prediction and classification tasks in an efficient manner. The major challenge for the miniaturization of photonic reservoir computing is the need for the use of photonic integrated circuits. Herein, we experimentally demonstrate reservoir computing using a photonic integrated circuit with a semiconductor laser and a short external cavity. We propose a method to increase the number of virtual nodes in delayed feedback using short node intervals and outputs from multiple delay times. We perform time-series prediction and nonlinear channel equalization tasks using reservoir computing with the photonic integrated circuit. We show that the photonic integrated circuit with optical feedback outperforms the photonic integrated circuit without optical feedback for prediction tasks. To enhance the memory effect we feed past input signals in the current input data and demonstrate successful performance in an n-step-ahead prediction task.

We retrospectively investigated the status of transfusional iron overload at Kinki University Hospital. One hundred and sixty three patients received more than 10 red blood cell (RBC) units per year in 2009 and 2010. Myelodysplastic syndrome (37.4%) and aplastic anemia (11.0%) accounted for about 50% of the underlying diseases. At the time of receiving a total of 20 RBC units, 90.8% and 66.2% of the 65 patients evaluated had more than 500 and 1,000 ng/ml of serum ferritin, respectively. The frequency of organ dysfunction associated with iron overload was 56.9% of all the patients assessed, 37.8% of patients with serum ferritin levels of 500∼999 ng/ml, and 67.4% of patients with serum ferritin levels >1,000 ng/ml. Although the Japanese guidelines propose 40 units of RBC transfusion and/or a serum ferritin level of 1,000 ng/ml as a good point to start iron chelation therapy, our results suggest that iron overload and consequent organ dysfunction may occur earlier than this. Therefore, it may be necessary to start iron chelation therapy earlier than that suggested by the Japanese guidelines.