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Performance of Second 50 Completed ATP Projects — Status Report Number 3 NIST Special Publication 950-3 (January 2006)
Telecommunication Networks Require High-Speed Capacity Advances in telecommunications occur at a rapid pace, but technological advances are sometimes uneven. This was the case when the use of fiber optics for transporting telecommunication signals began to expand rapidly within the industry in the early 1990s. Increased bandwidth demands could not be met with electronic networks. Prior to the start of this ATP project, millions of miles of fiber that carried long-range and local communications were already in place in the United States. However, there was a bottleneck problem in the electronic systems that were used to detect and switch signals at both ends of the fibers. Furthermore, increased bandwidth demands could not be met with electronic networks. It was anticipated that the use of all-optical networks would solve this problem. Networks were increasingly using a technique called wavelength division multiplexing (WDM), which uses optical rather than electronic systems. WDM involves using multiple laser wavelengths to carry many signals simultaneously . In the end, a machine is used that can translate the light back into binary signals if necessary. Century-Old Technology Updated for Optical-Fiber Networks
As fiber-optic applications technology continued to develop, it became clear that the direct optical processing of signals without conversion to electronic signals was required to sustain the speed necessary to keep up with the volume that was building in these systems. A fiber Fabry-Perot (FFP) interferometric filter is one component that can handle such an application. Direct optical processing of signals without conversion to electronic signals The Fabry-Perot was first described by C. Fabry and A. Perot in 1897. Fabry-Perot filters are constructed of bulk lenses, mirrors, and beam optics along with geared positioning stages. For more than 100 years, designs based on these original optical configurations have provided the highest known optical wavelength resolution. Other filter and tunable laser technologies offered the speed, but lacked either the tuning range or the resolution that was needed. Micron Optics added a single segment of fiber within the original Fabry-Perot device and patented the fiber Fabry-Perot tunable filter (FFP-TF). The FFP-TF is a simpler design, since it does not require complex optics and lenses; yet FFP-TFs are more robust and field-worthy than traditional Fabry-Perot interferometers. Since the early 1990s, Micron Optics has been the only supplier in the world of FFP components, including optical filters used as switches in optical-fiber networks. However, as progress was made in telecommunication networks and their usage grew, it became apparent that the packet-switching, all-optical networks planned for the future would require far more capability than what Micron Optics could produce in the early 1990s. The electromechanical (piezoelectric)-tuned FFP filters commercially available in the early 1990s had wide wavelength-tuning ranges, but their tuning speed was limited to the 1- to 10-millisecond range. This was 1,000 times too slow for packet-switching.(1) In addition, these filters were limited in capacity to between 50 and 100 channels, whereas a capacity approaching 1,000 channels was needed. Each filter cost thousands of dollars; however, widespread use could only be achieved if the cost was approximately $100. Therefore, to keep up with the capability of optical networks, it would be necessary to improve the tuning speed by a factor of 1,000, channel capacity by a factor of 10, and cost by a factor of 10. Micron Optics Designs a Faster Fiber Fabry-Perot Tunable Filter Micron Optics envisioned a highly optimized version of its FFP-TF that would be faster and could reach more channels by replacing the present piezoelectric-tuning mechanism with a ferroelectric liquid crystal (FLC) cavity capable of tuning the filter to the desired wavelength without requiring moving parts. The company sought to develop an FFP-TF with quicker tuning speeds and channel capacities approaching 1,000, (reaching a finesse, i.e., measure of sharpness, approaching 2,000) while costing only several hundred dollars per filter. This was an ambitious endeavor because the required improvement in performance was significant. Micron Optics wanted to develop an FFP-TF that used FLCs to tune the path length electro-optically in hopes that it would achieve packet-switching speeds that were three orders of magnitude faster than the piezoelectric device that was used for channel switching. The company sought to develop an FFP-TF withquicker tuning speeds and channel capacities With $1.895 million in co-funding from ATP, Micron Optics teamed with subcontractors, IBM and University of Colorado, in a three-year research program to achieve these performance and cost goals. The University of Colorado focused on the FLCs, and IBM provided a testbed for evaluating the new filters. The research program centered on evaluating the following:
Through its collaboration with ATP, the company was able to miniaturize the FFP-TFs. Micron Optics developed a prototype that demonstrated high-speed performance and low-cost fabrication. The new fabrication technique was an improvement over Micron Optics' previous technique, which required constant realignment. These improved FFP-TFs had higher finesses (>2,000), lower loss, lower mass and smaller size, good thermal and mechanical stability, and the potential for low-cost, high-volume production. Unfortunately, research into the high-speed FFP filters using FLCs resulted in minimal success. While these FFPs provided moderate improvements in wavelength tuning range, switching time, finesse, and total insertion loss, the device fell short of Micron Optics' originally proposed goals of quicker tuning speeds and increased channel capacities.With A TP support for research and development,Micron Optics responded to the needs of the For these reasons, at the conclusion of the ATP project in 1996, the company decided to focus its future development efforts on improving FFP-TFs that used piezoelectric-tuning mechanisms, and they spent no more effort utilizing FLCs. Strategic Alliances Result from ATP Funding Advances made during its ATP project allowed Micron Optics to form pivotal collaborative alliances in the post-project period with equipment and system developers for further development of optical filter technologies. The company formed a joint effort with Photo Kinetics, Inc., to develop optical channel analyzers for WDM applications based on high-performance FFP-TFs. Further, Micron Optics worked with the Massachusetts Institute of Technology Lincoln Labs on optical coherence tomography, an alternative to ultrasound imaging that can be used in sensor networks. Conclusion With ATP support for research and development, Micron Optics responded to the needs of the market at the right time by decreasing the cost of FFP-TF manufacturing by 99 percent. The prototypes built by Micron Optics helped the firm strengthen its position in the telecommunications market as well as expanding into new markets. Shortly after the project ended, the company began introducing its FFP-TF technology into the mechanical-sensing market through prototype-based marketing in early 1997. More recently, it has expanded into the optical performance and test equipment areas.
Research and data for Status Report 93-01-0027 were collected during October-December 2001. ___________________ Return to Table of Contents or go to next section of Status Report No. 3. Date created: April 4, 2006 |
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