Our Technology

Background: Avalanche photodiodes in Telecom and Datacom

Avalanche photodiodes (APDs) provide a cost-effective solution to receivers for Telecom and Datacom. An APD relaxes the power requirement for incoming optical pulses, which translates to longer optical links and/or higher bit rates. APDs are used, whenever their speeds permit, to improve the receiver sensitivity, which is the minimum optical power required at the receiver to achieve bit-error rates required by industry standards (10-9 or 10-12). Due to the APD’s traditional speed limitations, also termed the buildup-time limitation, which constrains the gain-bandwidth product, producing viable 25-Gbps APDs has been a challenge for the optical communication wavelengths of 1.3 or 1.55 micron.

 

Our Invention

Dynamic Photonics, Inc. (DPI) invented a revolutionary dynamic-biasing method for APDs that substantially raises the envelope for the speed-sensitivity trade-off in APD receivers well beyond the traditionally known limits.

  • It enables existing InGaAs avalanche photodiodes that are designed for 10Gbps to be adapted to operate at 25 Gbps.
  • The method can enhance gain-bandwidth-product (GBP) by a factor of 5 and the receiver sensitivity by up to 6 dB, thereby breaking the traditional GBP and sensitivity limits of APDs.
  • DPI’s method is device agnostic and can be applied to any high-speed APD, exploiting certain unexplored physics of avalanche-multiplication dynamics, which is DPI’s expertise.

DPI’s technology enables InGaAs APDs to penetrate the 25 Gbps (per channel) Telelcom and Datacom markets and beyond.

The primary innovation is the replacement of the traditional static bias voltage across the APD with a bit-synchronous, time-varying voltage. Our other innovations relate to implementation, in particular to ensuring that the dynamic bias voltage does not affect the photo-current, and hence the data recovery circuit. Our technology enables any APD receiver to operate at previously impossible rates. Testing has shown that DPI’s dynamic-biasing technology is capable of a 6db improvement in sensitivity. DPI has recently demonstrated that dynamic biasing enables the 25 Gbps operation of an off-the-shelf InGaAs-InP 10 Gbps APD operating at a speed of 25 Gbps. An example of the eye widening due to dynamic biasing for a 3Gbps APD is shown below.

A common metric for assessing the performance of an optical receiver is the “eye-diagram.” The more open is the eye, the less error is produced by the receiver. The figure on the left (top part) shows the eye-diagram for a typical germanium APD as it detects a 3 giga bits-per-second data data stream shown at the bottom of the figure. The figure on the right shows the eye-diagram for the exact same APD, albeit when operated using our dynamic-biasing technology. Notice the widening in the eye-diagram. For this example our experiments show that the error is reduced by a factor of 3,500 compared to the conventional case! This means we can pick an InGaAs-InP APD (used in telecom and Datacom applications) that is designed for 10 giga bits-per-second operation and make it work at the speed of 25 giga bits-per-second once we apply dynamic biasing to it (and of course after we package appropriately for the higher speeds).

A common metric for assessing the performance of an optical receiver is the “eye-diagram.” The more open is the eye, the less error is produced by the receiver. The figure on the left (top part) shows the eye-diagram for a typical germanium APD as it detects a 3 giga bits-per-second data data stream shown at the bottom of the figure. The figure on the right shows the eye-diagram for the exact same APD, albeit when operated using our dynamic-biasing technology. Notice the widening in the eye-diagram. For this example our experiments show that the error is reduced by a factor of 3,500 compared to the conventional case! This means we can pick an InGaAs-InP APD (used in telecom and Datacom applications) that is designed for 10 giga bits-per-second operation and make it work at the speed of 25 giga bits-per-second once we apply dynamic biasing to it (and of course after we package appropriately for the higher speeds).

The Market

The worldwide APD market is estimated at $200M per year and it is estimated to grow beyond $350M by 2019. The market for the DPI technology fits any high-speed (25 Gbps per channel) long-reach optical communication system where power is a limitation. These may include today’s 100Gb Ethernet, next-generation 400Gb Ethernet, PON (passive optical networks), GPON (Gigabit PON), Datacom, Datacenters, etc. DPI’s technology is an excellent fit to APD-on-silicon-photonics chips, and can also be incorporated in Si-Ge APD receivers to enhance the sensitivity for short range systems.

Intellectual Property

DPI has an intellectual property portfolio of four patents and patent applications. The core technology, invented by the DPI co-founders, has been patented (in 2016) and exclusively licensed from the University of New Mexico (UNM). The second UNM patent application covers various methods of implementation. DPI has also invented and solely owns other patent-pending technologies. The first DPI patent application applies the technology to alternate modulation schemes, and the second patent application covers improves upon implementations.

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