August 9, 2011 – Arlon Martin, VP of marketing, government contracts, and industry relations at Kotura, discusses the changes in processes that fabs will have to make when integrating silicon photonics onto chips to support optical circuits in a podcast interview with SST senior technical editor Debra Vogler. Such optical process modules will have to support waveguides at very low loss, as well as wavelength multiplexers/demultiplexers, modulation of the light, detection of the light, and other functions (e.g., variable optical attenuators, monitors, etc.), he said. When optical interconnects that use silicon photonics replace copper wires, the result is increased processing speed and reduced heat and energy consumption.
Examples of silicon photonics devices are shown in the figures below. In Fig. 1, the 500Gbs Tx chip couples to three bars of lasers (each bar has 4 lasers). All 12 lasers transmit at a different frequency of light. The 12 channels of light are combined by the fan-shaped reflector grating (mirror) in the upper left quadrant of the chip. The output waveguide (middle left) has all 12 channels on a single waveguide so that the chip can be connected to a single fiber.
Figure 1: A 500Gbs Tx chip. (Source: Kotura)
The Rx chip shown in Fig. 2 is the reverse of the Tx chip. The input fiber on the left contains 12 channels. When the signal from these channels hits the reflector in the upper left, they are demultiplexed into 12 channels. Detectors are attached to the chip on the right side, one for each channel.
Figure 2: A 500Gbs Rx chip. (Source: Kotura)
In the interview, Martin also provides details of how packaging processes and testing will have to change to accommodate silicon photonics. Though some silicon photonics devices are already in volume manufacturing (e.g., 100Gbit Ethernet transceivers, active optical cables, etc.), what will happen in the next several years, said Martin, is that transceiver chips will become more and more powerful in terms of performance. These chips will use less electricity and become more pervasive in the market space.