What Is a Photonic Integrated Circuit?

A photonic integrated circuit is a compactly packaged chip or electronic circuit that specializes either in the generation or in the processing of modulated light energy used in optical communications. It may also be classified according to the frequency band associated with the light energy used in the optical communications link. Before the year 2000, most optical communications equipment used separate semiconductor components and microchips for optical generators and converters and for electronic circuitry.

The term “photonic” refers to the photon, which is a particle of light energy. Early optical communications circuits used a fast optical beam modulator that is able to superimpose a fast bit stream as a series of light beams “on” and “off.” Digital devices used in electronics were incorporated with optical transmitters and receivers, resulting in the photonic integrated circuit. New photonic integrated circuit allows a more sophisticated photonic circuit design with lower component count. This means overall gains paired with lower costs for better performance.

For hauling huge amounts of data, the fiber-based optical communications is preferred over radio communications because the transmission of data as light energy is almost loss-free, which means the light energy is able to travel very far before the light intensity drops to a point where it must be regenerated or undergo reconstructive signal boost. While electrical signals will be attenuated by the coaxial cable or twisted pair, the optical fiber only gets attenuated to a minimal degree. Equivalent electrical data circuits will allow less data speed and shorter hop length. At the end of each hop, a regenerator will reconstruct the data onto a boosted signal that further travels to the next hop and so on.

Faster communication between gadgets like computers is made possible with optical links, which have the fastest data rates among the wired link types. Wireless optical links were used to a limited extent in the 1980s, but optical communications in open space was degraded during low-visibility weather conditions. The only perceived drawback of optical fibers is the physical access in the path where the cables are to be installed. A link for a 3-mile (5-kilometer) stretch over water between two islands may consider submarine optical fiber only if the data link speeds required are very high. For a few megabits per second, a digital microwave link is a better option.

By using the photonic integrated circuit, the flexibility of the optical network is increased. With less expensive equipment, it is now possible to connect, split, and merge optical networks with less cost. New photonic chips are able to add or drop high-speed data channels, which used to take complicated optical-electrical and electrical-optical converters that use up space and require significant investments. The photonic integrated circuit has increased the rate at which new optical links can be installed, commissioned, and reconfigured.