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36 DESIGN007 MAGAZINE I JANUARY 2025 stant and material loss. For example, FR-4 has a maximum speed of propagation of half the speed of light. Even the highest-grade materi- als with a very low dissipation factor (0.0002) don't significantly improve this. So, how do we overcome this limitation? e Lord said: "Let there be light"—and there was. Multilayer electro-optical PCBs use light rather than electrical energy to trans- mit data. is technology offers superior sig- nal integrity and achieves higher speeds and bandwidth at potentially greater distances than traditional copper circuits while also reducing losses and crosstalk from nearby cir- cuits. e electronic transmission of informa- tion requires energy. e faster the interface, the more electrical power is required. At very high data transfer rates, optical interfaces can be significantly more efficient than electrical ones. Additionally, the components within these boards benefit from secure isolation between layers, ensuring uninterrupted trans- mission, resulting in faster transmission speeds and higher overall performance. Electro-optical printed circuit boards (EOCBs) integrate optical and copper paths on the same board. While the copper paths distrib- ute power and direct low-speed data, the optical paths handle high-speed signals. is segrega- tion offers several advantages. At high frequencies, signal integrity suffers because of the skin effect, crosstalk, and skew when passing through copper systems. Optical systems do not have these issues and provide greater channel den- sity than copper. Furthermore, optical signals do not require sig- nal conditioning and equalization, resulting in lower power con- sumption compared to electrical signals. Additionally, optical sys- tems can reduce the surface area of a PCB by 20% and the number of layers on the multilayer board by up to 50%. Similarly, flexible-optical PCBs are becom- ing increasingly prevalent in modern elec- tronics. ey use specific transparent materi- als, such as acrylic or clear epoxy fixtures, and employ cutting-edge photolithography tech- nology and a patented etching technique. is enables the embedding of numerous optical fibers or waveguides necessary for the modula- tion and transmission of light signals through- out the circuit pathways. High-speed optical interconnects employ lasers, fiber optics, waveguide technology, and polarization components to send data directly from one interface to another without inter- mediate conversions or delays. is ensures high bandwidth capability and reliable, undis- torted signal transmission. e essence of this concept lies in achieving three-dimensional optical routing at the board level using EOCBs combined with electro-optical transceivers. A photonic integrated circuit (PIC) or integrated optical circuit is a microchip con- taining two or more photonic components forming a functioning circuit. This technol- Figure 1: NVIDIA Blackwell B200 GPU. Source: NVIDIA