Free space optical switching systems and photonic computing systems utilize macroscopic optical elements such as holograms, gratings, lenses, mirrors, and fiber optic arrays as basic building blocks. In such systems information is carried by arrays of light beams that are collimated, manipulated, and focused onto spatial light modulators in a stage by stage fashion. Fiber optic arrays may serve as input terminals, output terminals and interstage couplers for such systems. Precision fiber optic arrays are important support components of such systems.
Examples of known optical switching systems and photonic computing systems are known from: "An All Optical Shift Register Using Symmetric Self Electro-optic Effect Devices," published in OSA Proceedings on Photonic Switching, Vol. 3, pp. 192-195, 1989, edited by J. E. Midwinter and H. S. Hinton, "An All Optical Realization of a 2.times.1 Free Space Switching Node," published in Photonics Technology Letters, No. 8, 1990, pp. 600-602 by E. Kerbis, T. J. Cloonan, and F. B. McCormick; "An All Optical Implementation of a 3D Crossover Switching Network," published in Photonics Technology Letters, No. 6, 1990, pp. 438-440 by T. J. Cloonan, M. J. Herron, F. A. P. Tooley, G. W. Richards, F. B. McCormick, E. Kerbis, J. L. Brubaker, and A. L. Lentine; "Module for Optical Logic Circuits using Symmetric Self Electro-Optic Effect Devices," published in Applied Optics, No. 14, 1990, pp. 2164-2170 by M. E. Prise, N. C. Craft, R. E. LaMarche, M. M. Downs, S. J. Walker, L. A. D'Asaro, and L. M. F. Chirovsky; "Parallel Interconnection of Two 64.times.32 Symmetric Self Electro-optic Effect Device Arrays," published in Electronics Letters, No. 20, 1991, pp. 1869-1871 by F. B. McCormick, F. A. P. Tooley, J. M. Sasian, J. L. Brubaker, A. L. Lentine, T. J. Cloonan, R. L. Morrison, S. L. Walker, and R. J. Crisci; "Optomechanics of a Free Space Switch: The System," published in Optomechanics and Dimensional Stability, Proceedings of SPIE, No. 1533, 1991, pp. 97-114 by F. B. McCormick, F. A. P. Tooley, J. L. Brubaker, J. M. Sasian, T. J. Cloonan, A. L. Lentine, S. J. Hinterlong, and M. J. Herron; "Experimental Investigation of a Free Space Optical Switching Network Using S-SEEDs," published in Applied Optics, Vol. 31, No. 26, 1992, pp. 5431-5446 by F. B. McCormick, F. A. P. Tooley, T. J. Cloonan, J. L. Brubaker, A. L. Lentine, R. L. Morrison, S. J. Hinterlong, M. J. Herron, S. L. Walker, and J. M. Sasian; and "A Six-Stage Digital Free-Space Optical Switching Network Using S-SEEDs," published in Applied Optics, Oct. (1992) by F. B. McCormick, T. J. Cloonan, F. A. P. Tooley, A. L. Lentine, J. M. Sasian, J. L. Brubaker, R. L. Morrison, S. L. Walker, R. J. Crisci, R. A. Novotny, S. J. Hinterlong, H. S. Hinton, and E. Kerbis. These articles chronical the progress of optical and photonic system technology as it grows in complexity and functionality.
The potential of free space optical switching systems to interconnect a larger number of communication channels at high bit rates has spurred the development of such systems. The potential of photonic computing systems for increased processing rates and bit transfer rates through the use of optical and photonic components has spurred similar photonic computing system development. These potential benefits have motivated the development of high precision fiber optic arrays to communicate light beam borne data to and from free space optical switching systems and photonic computing systems. High precision fiber optic arrays have been easy to specify, but difficult to physically realize, especially if high precision positioning of the optical fibers is required. Several fabrication techniques have been reported in various publications. For example, Miller describes a 2-D array of optical fibers that was made by stacking a number of linear arrays of optical fibers that were supported by grooved spacers in "A Fiber Optic Cable Connector," The Bell Technical Journal, Vol. 54, No. 9, 1547-1555, 1975. These spacers were manufactured by the precise etching of grooves in both sides of a silicon wafer, potting all the optical fibers in place and polishing the resulting assembly. This technique has been used to assemble a fiber array with a maximum positioning error of 10 micrometers as reported by U. Danzer, P. Kipfer, K. Zufi, J. Lindolf, and J. Schwider, in "High Precision Two Dimensional Fibre Array in Silicon V-Groove Technique," Angewandte Optik, Physikalisches Institut der Universitat Erlangen, Annual Report 1992.
In another effort, an alignment-free assembly technique has been developed where fiber end positioning to within plus or minus 8 micrometers was achieved. This technique is described by A. Sasaki, T. Baba, and K. Iga in "Put-in Microconnectors for Alignment-free Coupling of an Optical Fiber Array," IEEE Photonics Technology Letters, Vol. 4 No. 5, pp. 908-910, 1992. In this known technique, an array of sockets with centering plugs for optical fibers were micro-fabricated to achieve self-centering of each optical fiber upon insertion and to expedite assembly also.
G. A. Koepf and B. J. Markey describe another technique involving arrays of precision holes in substrates to insert and locate optical fibers with a standard deviation of 12.6 micrometers in, "Fabrication and Characterization of a 2-D Fiber Array," Applied Optics Vol. 23, No. 2, pp. 3515-3516, 1984. Fiber optical arrays using precision holes to position the optical fibers have also been described by Basavanhally in "Opto-mechanical Alignment and Assembly of 2-D Array Components," Technical Digest of the IEEE Princeton Section Sarnoff Symposium, Mar. 26, 1992. G. M. Proudley, C. Stace, H. White also describe their fiber optic array fabrication technique in their article "Fabrication of 2-D Fibre-Optic Arrays for an Optical Crossbar Switch," submitted to Optical Engineering.
Koyabu, F. Ohira, T. Yamamoto, and S. Matsuo have realized a 2-D fiber optic array with a mean fiber positioning error of 3 micrometers by inserting the optical fibers into microferrules and stacking the fiber optic and microferrule assembly to create the array. This technique is described in their article "Novel High Density Collimator Module," Technical Digest, Conference on Optical fiber Communication/International Conference on Integrated Optics and Optical Fiber Communication, 1993 Technical Digest Series, Vol. 4, (Optical Society of America, Washington, D.C., 1993), pp. 2-3.
A common feature of these known techniques is that the final positioning of each optical fiber is accomplished by referencing each optical fiber to a mechanical jig or support through which the fibers pass. Thus, the precision of this mechanical jig or support limits the ultimate precision attainable. These known techniques, with their inherent mechanical limitations, are not precise enough to meet the requirements of the developing optical switching systems and the photonic computing systems. Thus, there is a need in the art to provide a high precision fiber optic array and a process for producing such an array.
It is an object of the present invention to provide a fiber optic array that is not limited by the precision of the mechanical support through which the optical fibers pass.
It is another object of the invention to provide a process for producing a high precision optical fiber array.