Optical waveguides – Optical fiber waveguide with cladding
Reexamination Certificate
1999-07-20
2001-12-04
Ullah, Akm E. (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
C385S015000
Reexamination Certificate
active
06327411
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optical devices and, in particular, to optical devices comprising two or more device components interconnected by optical fiber. It provides a structure for enhancing the reliability and quality of the fiber interconnection.
BACKGROUND OF THE INVENTION
A variety of devices used in optical systems comprise two or more device components interconnected by optical fiber. For example, a light source, such as a laser, may require a dedicated fiber connection to a polarizer, filter, attenuator, modulator or amplifier. In optical communication systems many applications of such devices, e.g. undersea cable, require an interconnection that is highly reliable and high in optical quality.
A typical interconnected optical device comprises a pair of device components, such as an LED and a filter, interconnected by an optical fiber. The optical fiber comprises a glass optical fiber waveguide typically covered with an outer polymer coating. In the present practice, the polymer coating has a thickness equal to the radius of the glass waveguide, i.e. if r
0
is the radius of the glass waveguide and r
1
is the radius of the coated waveguide, then the coating thickness t=r
1
−r
0
. The coated fiber is typically enclosed within a protective capillary tube extending between the device components.
The device is fabricated by bonding and/or soldering at elevated temperatures. The fiber is bonded between the device components at elevated temperature and then permitted to cool to ambient temperature.
A problem that reduces the reliability and quality of interconnected optical devices arises from the tendency of the fiber to buckle within the tube. The material of the tube typically has a higher coefficient of thermal expansion (CTE) than the glass of fiber, with the consequence that after cooling from fabrication at elevated temperature, the fiber is placed under compressive stress. This compressive stress can produce buckling of the fiber within the interior of the tube. The buckling increases the risk of fiber fracture and the induced curvature deteriorates the quality of the fiber as a waveguide. Accordingly, there is a need for interconnected optical devices of enhanced reliability and interconnection quality.
SUMMARY OF THE INVENTION
This invention is predicated on applicant's discovery that the conventional polymer coatings are often too thin to prevent buckling and subsequent bending of optical interconnection fiber, and that this buckling and bending can be eliminated by increasing the thickness of the fiber polymer coating. Applicant has further discovered that a thicker coating insufficient to prevent buckling, reduces stress should buckling occur, thereby still improving the reliability and quality of the waveguide. The optimal (minimum) polymer thickness for buckling prevention can be calculated in terms of the properties of the fiber, the coefficient of thermal expansion (contraction) of the tube materials and the thermal history of the device. Increased thicknesses less than this optimal thickness can nonetheless reduce stress should buckling occur.
REFERENCES:
patent: 4113350 (1978-09-01), Haines
patent: 4756600 (1988-07-01), Ramsay et al.
Workshop on Mechanical Reliability of Polymeric Materials and Plastic Packages of IC Devices, ASME 1998, EEP-vol. 25, 1998, “Coated Optical Fiber Interconnect Subjected to the Ends Off-Set and Axial Loading”, E.Suhir, pp. 301-333.
Suhir, E., “Elastic stability, free vibrations, and bending of optical glass fibers: effect of the nonlinear stress-strain relationship”,Applied Optics, vol. 31, No. 24, Aug. 20, 1992, pp. 5080-5085.
Suhir, E., “Stresses in Dual-Coated Optical Fibers”,Transactions of the ASME, vol. 55, Dec. 1988, pp. 822-830.
Suhir, E., “Spring Constant in the Buckling of Dual-Coated Optical Fibers”,Journal of Lightwave Technology, vol. 6, No. 7, Jul. 1988, pp. 1240-1244.
Suhir, E., “Effect of Initial Curvature on Low Temperature Microbending in Optical Fibers”,Journal of Lightwave Technology, vol. 6, No. 8, Aug. 1988, pp. 1321-1327.
Shiue, Sham-Tsong and Lee, Sanboh, Thermal stresses in double-coated optical fibers at low temperature,J. Appl. Phys., 72(1), Jul. 1, 1992, pp. 18-23.
Shiue, Sham-Tsong, “Axial strain-induced microbending losses in double-coated optical fibers”,J. Applied Phys., 73(2), Jan. 15, 1993, pp. 526-529.
Shiue, Sham-Tsong, “The Axial Strain-induced Stresses in Double-Coated Optical Fibers”,Journal of the Chinese Institute of Engineers, vol. 17, No. 1, 1994, pp. 143-149.
Shiue, Sham-Tsong, “The spring constant in the buckling of tightly jacketed double-coated optical fibers”,J. Appl. Phys.81(8), Apr. 15, 1997, pp. 3363-3368.
Agere Systems Optoelectronics Guardian Corp.
Connelly-Cushwa Michelle R.
Lowenstein & Sandler PC
Ullah Akm E.
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