Reaping the Evanescent Field

Modern fiber-optic cable, despite its gigabit-per-second capacity, is still just a big pipe carrying light that is switched and routed by some other mechanism. No longer; the fiber can do its own switching now at the speed of light.

Intelligent Fiber Optic Systems (IFOS; Sunnyvale, CA) has developed products that could mark the transition to true all-optical communications, computing, and sensing. IFO takes conventional fiber-optic cable and, using patented designs and processes called FyberSpace™, modifies both the core and the cladding. The result is fiber that performs integrated functions outside of simple transport such as add-drop multiplexing, variable attenuation, filtering, modulation, and switching.

Optical processing within a fiber-optic cable provides more capacity within a smaller housing and eliminates the burden of electronic components. BMDO, now MDA, was interested in supporting IFOS research and awarded the company a Phase I SBIR contract in 1998 and a Phase II contract in the last quarter of 1999. In Phase I, IFOS successfully fabricated and proved optical add-drop multiplexing. In Phase II, the company showed that conventional fiber could be modified cost-effectively and packaged to be attractive to potential customers in the photonics industry. IFOS is now evaluating the performance and reliability of the product at both the device and network levels.

The heart of IFOS technology is the ability to manipulate what is called the evanescent field. Light travels as an electromagnetic wave through the core of a fiber called a waveguide. Most of the energy of the wave is propagated through the waveguide, but a small "tail" of energy--the evanescent field--extends a few microns outside the guide and into the less dense cladding. If two waveguides are brought into close proximity such that the evanescent fields overlap, under special conditions of separation and interaction length, the energy can switch back and forth between the waveguides.

By thinning fiber cladding very precisely and optically contacting the thinned faces of two strands, IFOS takes advantage of a phenomenon known as evanescent wave coupling to create a coupling mechanism. Light passes through or is redirected from one fiber strand to another. Modifying fiber with micron-level precision for high performance device applications would be impossible without the help of sophisticated simulation software.

IFOS technology can be either passive or active. Using fiber gratings, IFOS technology can perform static network routing and management functions. Using active optical materials as the activation mechanism, it would be possible for a network operator to "reprogram" the fiber to perform a different specific function.

Whether something works in the laboratory and again in the field under harsh conditions are two different questions. The reliability of "intelligent" fiber needs to be proven before network providers will deploy it. IFOS is manufacturing batch samples for testing to standards established by Telcordia Technologies, which industry engineers recognize for performance qualification. After testing, the company intends to ship products to customers for direct use in deploying new or replacement fiber-optic networks. IFOS is closely working with customers to optimize products for specific applications.

Optical sensors also benefit from IFOS FyberSpace technology and products, which need no distributed electronics. The company claims that any mechanism or structure that benefits now from sensors could substitute IFOS fiber for sensors and save on cost and weight.

The company seeks approximately $5 million in investment funding to purchase manufacturing equipment that would enable them to quickly and efficiently meet anticipated demand over the next few years. The company also welcomes inquiries on new research projects based on FyberSpace technology that need funding.

--A. Gruen