Hiromi Kurashima

EMI suppression of 10Gbit/s optical transceiver by using EBG structure

The fiber optic data transmission system plays an important role in broadband communication. According to the market trend, data traffic is significantly increasing and larger throughput of communication systems is required. Many opto-electronic conversion devices (so called optical transceivers) are used in the system. Because of that, the electro-magnetic noise radiation becomes a serious consideration. Although noise level is proportional to the number of transceivers, a qualitative relationship between the number of transceivers and emission level is not clear. Furthermore, since theres no general design guideline to suppress EMI, it is difficult to solve this problem once it emerges. In these circumstances, recent dispersion control technology such as Electro-magnetic Band Gap (EBG) is a potential solution for this problem. In this paper, the method of how to predict total emission level with the superimposed effect of thousands of transceivers and how to determine the EMI suppression design target are described. Then, the method of how to reach the goal with a newly introduced shielding scheme is described. And, it is demonstrated that the EBG structure is suitable for optical transceivers. Its verification is shown by utilization of FEM/FDTD simulation and an experiment of an in-house prototype.

Development of a practical electro-magnetic interference (EMI) simulation in high speed optical transceivers

The growing bandwidth of optical communication systems has made great improvements to information technology infrastructures. However, electro-magnetic compatibility becomes an issue due to the high frequency of the components. EMI problems occur due to the miniaturization and high density of the Printed Circuit Board (PCB) mounted on the system. Generally, electro-magnetic radiation is generated by the circuit elements. For example, switching in the LSI raises the voltage swing between the power source and ground which is known as “ground bounce”. EMI problems related to the ground and power source are linked to the power integrity, and is influenced by the structure of the patch antenna parasitically existing between the power source and ground. That is to say, most of the time this problem can be solved by utilizing the appropriate power source and ground pattern layout at the PCB design stage. However, high speed digital signals measuring at more than 10 Gigabit per second (Gbit/s) typically have high frequency components in excess of 40GHz. There is little feasible knowledge available that illustrates guidelines for the perfect layout method to prevent the emission on the PCB for such a high frequency application. Therefore, we focused on the Finite Element Method used in the 3D electromagnetic field analysis simulator so that we could solve the emission within the frequency domain. We first correlated both qualitatively and quantitatively the actual measurements and the simulation results. Then we investigated the countermeasure for the emission intensity (EMI level) from the 10 Gbit/s optical transceiver by simulation and then verified it.