Gary J. Grimes

A molded polymeric resin-filled coupler

A novel type of molded polymeric resin-filled coupler has been built with the goal of making a low cost and manufacturable 1*N multimode optical coupler. The coupler consists of a low index thermoplastic molded cladding piece part containing an optically finished waveguide channel. The channel is covered with a flat lid of the same material and is filled with a high index resin to form a mode mixing waveguide. Optical fibers are inserted into both ends of the channel before it is filled to complete the pigtailed device. The design accomplished all required tasks with just two materials: the molded low index structural part which provides the waveguide cladding, and the high index waveguide core part which provides the adhesive to hold the fibers in place and the optial refractive index matching to reduce reflections. Two different material systems have been used to construct 1*23 couplers. Typical coupler excess losses are less than 2 dB, and the uniformity among all fibers is better than a 1 dB standard deviation. >

Packaging of optoelectronics and passive optics in a high capacity transmission terminal

We report on the first circuit board having passive optical circuits in combination with a backplane multifiber array connector. The approach uses four fused biconical tapered optical couplers in combination with a 12 fiber multifiber array connector. The design makes possible fiber continuity from the tips of the discrete optical connectors all the way through the assembly of the couplers to the tip of the multifiber array connector. This is accomplished by building an optical fiber ribbon cable from the fiber pigtails on the couplers and inserting the ribbon into a multifiber array connector. This approach enhances reliability and minimizes optical loss and reflections.<<ETX>>

Excimer laser machining of optical fiber taps

Precision openings for construction of an optical backplane have been machined in an optical fiber using an excimer laser operating at a wavelength of 193 nm. The openings were made by imaging the laser beam onto the polymer fiber cladding with a telescope, then ablating the cladding with a sufficient number of pulses to expose the core. Circular openings measuring 250 and 625 microns and elliptical openings measuring 650 X 350 microns have been made in the cladding of a 1 mm polymer-clad silica fiber. Examination by scanning electron microscopy reveals that the best quality openings are obtained with either the smaller circular geometry or the elliptical geometry. For various reasons, elliptical openings, with the major axis oriented along the longitudinal axis of the fiber, appear more suitable for tap construction. Individual optical fiber taps have been constructed by attaching a tap fiber to a laser machined opening in a central fiber using an ultraviolet-curable acralate. Individual tap measurements were made on the elliptical and the 250 micron circular openings. In addition, a triple tap assembly was made using elliptical tap openings. These results indicate that the excimer laser machining technique may be applicable to the construction of a linear tapped bus for optical backplanes.

Mode mixing and polarization scrambling microparticles in polymeric resin filled optical couplers

The fiber-to-fiber uniformity, optical loss, and size of polymeric multimode combiners and splitters was enhanced by the addition of mode mixing microspheres when low numerical aperture (NA) sources were used. Mixing rod type resin filled polymeric optical couplers could be significantly shortened when used with small beam divergence angle lasers and other small NA sources. The small NA beam divergence angle causes the energy to remain in low-order modes for desired mixing lengths, causing fiber-to-fiber nonuniformity. A solution to this problem a mode mixing refractive microsphere technology, is presented. Results demonstrate that the use of the microspheres improved the performance of both optical splitters and combiners. Silica microparticles were suspended in the polymer mixing regions of the couplers. The shortened mixing lengths accomplished with the microparticles also makes it possible to use polymeric couplers with longer wavelengths of light where polymers are not as transparent. >

Polymeric resin-filled optical couplers with mode mixing and polarization scrambling microparticles

It was found that the performance of polymeric multimode combiners and splitters could be enhanced by the addition of mode mixing microspheres. The microparticles were silica, which had a slightly different index of refraction (1.46) than that (1.40) of the silicone polymeric material in which they were suspended. This index difference causes both refractive and diffractive mode mixing effects. The refraction and diffraction causes light to be scattered preferentially into higher-order modes. When propagating light reaches equilibrium and uniformity in the propagating modes, it is known that in large, high-NA , step index waveguides the power distribution across the aperture of the waveguide is also uniform. This means that the couplers can achieve the fiber-to-fiber uniformity required to make both combiners and splitters. Loss and near-field uniformity measurements of large polymer waveguides excited by a relatively small collimated HeNe laser have been carried out. Uniformity measurements of complete 1*7 splitters containing a visible diode laser are also presented. The application of this technology to a polymeric photon switch is discussed.<<ETX>>

Control of synchronization within an ISDN-compatible distributed PBX

In a distributed PBX, synchronization control is typically complex and requires a centralized dynamic database of system status. An algorithm is described which allows relatively simple distributed control of synchronization. Each node communicates timing information only with its nearest neighbors.<<ETX>>

Plastic-optical-fiber-based photonic switch

Polymer waveguide technology was exploited to build a photonic switch with enormous bandwidth capabilities at extremely low cost per path. A 6 X 6 ferroelectric liquid crystal array was used as a switching element to block or transmit light signals between input and output fibers. Visible laser sources, plastic fibers, PIN detectors, and our proprietary polymeric mixing rod couplers were used to construct the switch. The polymeric fibers, couplers, and switching element allowed us to eliminate the need to time division multiplex photonic channels through the switch because the optical paths were no longer costly. This in turn eliminated the electronic buffering and synchronization requirements of the switch.