A great increase in the effectiveness of fiber optic systems is possible with a device that allows for simultaneous two-way signalling of multiple data streams on a single optical fiber. By using a highly efficient multijunction solar cell to emit as well as detect two or more distinct wavelengths within a broad band of near-infrared (0.93-1.65-micron) light, this new technology provides such a capability and many others.

Diagram of the Multicolor Transceiver. Eg stands for bandgap energy. The top layer might be straight indium phosphide with a relatively high bandgap of 1.35 eV (0.93-micron wavelength). Light of that frequency is detected by that layer; lower-energy light passes through that layer to be detected by lower layers. The bottom layer might be straight gallium indium arsenide with a relatively low bandgap of 0.75 eV (1.65-micron wavelength). Intermediate layers would have varying percentages of phosphide and gallium arsenide to detect intermediate bandgap/wavelength light.

NREL scientists have developed a single-crystal multicolor light emission and detection device that is capable of simultaneously transmitting and receiving multiple optical signals. The underlying technology for this optical transceiver capability is a lattice-matched monolithic device with multiple layers of thin-film P-N junction InP/GaInAs varied in composition so that each layer has a different bandgap and therefore a different wavelength. With two layers, a pair of tandem devices can each simultaneously transmit and receive. With a multiple cascade of decreasing bandgap layers, numerous separate data streams can be transmitted by a single device on a single fiber or other optical medium. The technology could be used for optically coupled circuits within microelectronic systems, for long-distance optical fiber communication systems, or for any optical communication use. The ability to transmit and receive multiple independent signals should greatly increase data transmission rates and simplify optical interconnections and networks compared to current optical transceivers. This should allow significantly improved performance or cost and space savings for a wide variety of equipment.

The Multicolor Optical Transceiver can be fabricated with currently available manufacturing equipment such as this metallorganic chemical vapor deposition reactor.

NREL's multicolor transceiver uses materials and epitaxial fabrication methods widely employed in the manufacture of near-infrared lasers, so it should be easy to produce. It should also substitute directly for less effective monochromatic devices currently in use. With more than nine years of experience in developing InP/GaInAs tandem solar cells, NREL has the expertise to facilitate setup of effective manufacturing processes and is seeking industry partners to develop valuable uses of the technology. The principal patent number is 5,391,896.

The lead researcher for development of the multicolor transceiver is Mark Wanlass of the National Renewable Energy Laboratory. Inquiries concerning the patent status and availability of rights and licenses should be directed to NREL's Business Ventures Center; (303) 275-3009; E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..

Photonics Tech Briefs Magazine

This article first appeared in the February, 1998 issue of Photonics Tech Briefs Magazine.

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