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Optoelectronics & Communications

PATENTS: All-optical? Why not all-photonic?

The latest featured patent review by analysts from Nerac.
13 February 2007, SPIE Newsroom. DOI: 10.1117/2.200702.0002
The all-optical network is a chimera that the telecom world has been pursuing for over a decade. In the hybrid copper/fiber networks that predominate today, network speed is bottlenecked by electronics. The optical signal must be translated to an electronic signal for any switching or routing, and, typically, is translated from optical to electronic at the point of ultimate delivery to the customer. Such systems' speeds are limited by electrical switches and drivers.
With an all-optical system, the signal never needs to be translated from light to electricity. Total system speed is greater, and the signal is cleaner. One after another, the big fiber-optics companies jumped on the all-optical switching bandwagon. Lucent, JDSU, NTT, Corning, and myriad smaller players all have been involved in developing all-optical switching. Thousands of all-optical devices and systems have been applied for and patented; indeed, over 1,300 US applications containing the term "all-optical" have been published since 2001, and over 1,000 US patents have been granted since 2000.
This January, a U.S. patent was granted to Main Street Ventures, LLC for "All-optical bi-stable devices". Main Street Ventures holds a modest U.S. patent portfolio of all-optical component patents. These patents were acquired from Prima Luci, one of the early all-optical switching companies. Prima Luci's co-founder and once primary inventor, Arie Shahar, is the author of the new bi-stable device patent. Prima Luci (Latin for "first light") differs from the throng of all-optical switch companies by virtue of claiming what it calls an "all-photonic" technology. The equipment is not merely all-optical, a term which implies that the signal itself remains an optical signal through the switching process, but also photonically controlled. Most optical switches use a mechanism that must be electronically actuated one way or another - by MEMS, liquid crystal, something that ultimately requires electronic actuation. All-photonic technology is a different beast entirely, totally independent of electricity.
Unfortunately, Prima Luci's technology is perhaps a little too different for the market so far. The company declared bankruptcy in late 2005 and announced that it would sell its intellectual property portfolio in March 2006. Main Street Ventures has acquired at least 12 of the Prima Luci patents so far. "All-optical bi-stable devices" is the most recently filed patent document in their collection.
The abstract of U.S. 7,162,121 "All-optical bi-stable devices" reads as follows:
"An all-optical bi-stable device includes first and second comparators, each having an activating input, a threshold input, and a clamping output; a first optical path between the first clamping output and the second threshold input; a second optical path between the second clamping output and the first threshold input; at least one tapping device; and at least one coupling device. The comparators are arranged to produce at the clamping output either a high-level clamped output signal or a low-level output signal, based on a comparison of signals received at the activating and threshold inputs. The first and second optical paths may create one of two stable states in which one of the comparators produces a high-level clamped output signal and the other comparator produces a low-level output signal. The coupling device may flip between the two stable states by converting the high-level clamped output signal into the low-level output signal."
Implied in this summary, though not stated in an obvious manner, is the fact that every signal, every source, every component involved is optical. Nothing in the comparators that are the heart of this device requires a voltage, nothing requires a power supply. This technology is true O-O-O (optical-optical-optical) technology, and even a step beyond. There are a few O-O-O component vendors in the market (Calient has apparently shipped thousands of switches; see http://www.gridtoday.com/grid/395283.html, and has patented quite a few optical switch designs), but Calient and most of the other O-O-O folks are using MEMS, which are, of course, electrically powered. Perhaps the time is yet to come for a truly all optical, all optically controlled, "all-photonic" network.
Margaret Fiore is a Nerac Patent Analyst. Nerac's Intellectual Property Solutions provide a practical understanding of the IP landscape, helping organizations to make informed decisions about R&D planning and business strategy development. Nerac analysts work with clients in the following critical areas:
  • Patentability and Invalidity
  • Patent Portfolio Analysis
  • Commercialization Strategy
  • White Space Analysis