Vol.4 No.2 2011
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Research paper : Demonstration of optical communication network for ultra high-definition image transmission (J. Kurumida et al.)−118−Synthesiology - English edition Vol.4 No.2 (2011) 1. The three viewpoints explained in chapter 3, were clarified as A, B and C, with the introduction “we shall discuss the issue from the three perspectives” I matched them to the explanation in chapter 6.2. Since I provided a specific figure for the distance of the optical fiber line in subchapter 5.1, I added the story about the difficulty of high-speed communication over distance: “This distance was suitable as a network model connecting the area within a city. The major issue was to establish the communication by the 43 Gb/s optical modulation signal, the fastest signal used in the demo. Therefore, we planned the complete compensation for the effect of signal degradation by wavelength dispersion in the 105 km of optical fiber, using the high-speed autonomous control tunable dispersion compensator that we developed. However, since the transmission loss at 0.2 dB/km or more in the optical fiber and the loss due to optical connectors and parts were unknown, it was uncertain whether the optical S/N ratio would fall within the acceptable range of the receiver. Therefore, we prepared a backup plan to decrease the difficulty of the transmission for the video distribution demo based on the simplification of the topology.”In response to the above, I described the important point that we overcame in the demo experiment in subchapter 5.2: “One of the highlights of the demo experiment was to see whether the path communication for 43 Gb/s, the fastest optical modulation signal, was possible over the 105 km transmission distance. This is the communication path shown as a red line in Fig. 3. When the path was tested by a bit error rate tester, it did not become error free even when the optical signal intensity was raised and we were concerned about the disturbances or interruptions in the SHV video. However, when the actual connection was made with the receiver with appropriate optical power, the communication was established due to the signal error correction function of the device. Although the signal error correction function was nothing special, whether the 43 Gb/s path at transmission distance 105 km would fall into the error correctable range could only be confirmed by the experiment, and this was a major point of the video distribution experiment.”3 Vertical integration (collaboration) and its conceptComment (Naoto Kobayashi)I think the “vertical integration (collaboration)” is one of the most valuable points in this research, and I think you should include a simple explanation along with a figure.Answer (Junya Kurumida)Thank you for your indication. I added Fig. 1 and the explanation for the figure as follows: “Figure 1 shows the conceptual diagram. To utilize the optical switch in the network, a mechanism for controlling the optical switch according to the network application is necessary. That is to say, a mechanism is needed where the mutual connections are made between the HD video server and display, teleconference systems are handled, and these are appropriately managed according to the optical path and storage information. Moreover, vertical integration (collaboration) is essential to introduce the silicon optical path switch and wavelength resource management technologies, and to consolidate and realize the technologies that are developed individually, from device level to application level.”4 Evaluation of the resultComment (Hiroshi Tateishi)Chapter 6 is an important part for Synthesiology, but the description is insufficient. What are the meanings of the problems that occurred in the experiment and how were they solved? Moreover, what significance do they have in the future development? As of now, you’re saying, “When we did the experiment, many unforeseen problems occurred, but we could not solve all of them on the spot”. It is merely a report of the results without much information for the reader.Also, there is no evaluation for “power consumption 1.5 kW”. When I see Fig. 6, I can understand that it can be reduced further compared to the electric signal processing, but you need the explanations for, “to which extent you have to decrease in practice?” and “were the results sufficient or insufficient?”Answer (Junya Kurumida)I added the description on the specific problems that occurred in the experiment and the solution process in the beginning of the video distribution experiment in subchapter 5.2. I added the process of establishing the communication with 43 Gb/s path, the optical modulating signal with highest speed in this demo, with 105 km transmission distance.Also, in the beginning of chapter 2, I added the detailed description of the communication traffic and electricity: “Assuming that this trend will continue for about 20 years, the traffic will be about 1,000 times higher. This calls for the improvement of power efficiency.” Building on this comment, I added the following section as the evaluation of the power consumption in chapter 6: “Assuming that the switch ports and nodes were set up for the same number of devices used in the demo experiment using the core router, it was estimated to be about 13.4 kW including the optical amplifier. In the demo experiment, the power excluding the server was 1.5 kW with room for expandability to Tb/s.” and “Specifically, when the transmission rate per port becomes100 Gb/s as the silicon photonics optical switch is realized, it is estimated that power efficiency 1,000 times higher may be achieved. Considering the increased communication demand such as for HD video expected in the future, we believe sufficient decrease of power consumption was achieved, as we are able to slow down the increase of power consumption.”

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