Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Process of manufacturing optical fibers – waveguides – or...
Reexamination Certificate
1998-07-24
2003-04-22
Hoffman, John (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Process of manufacturing optical fibers, waveguides, or...
C065S504000, C057S335000, C057S293000
Reexamination Certificate
active
06550281
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to methods for introducing controlled spin in single mode optical fiber so as to reduce polarization mode dispersion (PMD).
It is well known that the so-called “single mode fiber” that is commonly used in communication systems is not purely single mode. Rather, when light at a particular wavelength propagates through a single mode fiber, two modes, with perpendicular polarizations, exist in the fiber. Light that propagates through a single mode fiber can be represented by a linear superposition of these two modes. If the fiber is perfectly circularly symmetric, in geometric and in stress symmetries, the two polarization modes are degenerate. They propagate with the same group velocity and have no time delay difference after traveling the same distance in the fiber. However, an actual fiber is not perfectly circularly symmetric. Any circular asymmetry which alters the propagation constant of the fiber with respect to the two orthogonal modes breaks the degeneracy of the two modes. These asymmetries may be geometric or stress induced. As a result, the two polarization modes propagate with different propagation. constants. The difference between the propagation constants is termed birefringence. The birefringence causes a general polarization state to evolve periodically along the fiber. The length over which the polarization state is reproduced is the fiber beat length, which is inversely proportional to the fiber birefringence. When birefringence is present, the two polarization modes travel at different group velocities. The differential time delay between the two polarization modes is called polarization mode dispersion, or PMD. PMD causes signal distortion which is very harmful for high bit rate systems and analog communication systems.
It is also known that PMD may be reduced if the polarization modes “couple.” Mode coupling occurs when the light energy from one polarization mode couples to the other polarization mode. This occurs if the longitudinal uniformity of the fiber is not perfect. Such longitudinal uniformity can be disrupted by errors in core circularity in preform fabrication or the drawing process, or by bends and twists when the fiber is deployed.
The present invention provides a method and apparatus for spinning fiber about its longitudinal axis, while it is being drawn, to form rotational non-uniformities in the fiber.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for reducing PMD.
It is a further object of the present invention to provide a controllable and predictable method and apparatus for spinning fiber during the drawing process.
It is an object of the present invention to provide a method for reducing PMD in a fiber, when it is used, by spinning the fiber in a controllable and predictable manner during the fiber drawing process, so as to cause mode coupling when the resultant fiber is used.
The above objects are achieved by the present invention.
REFERENCES:
patent: 3659408 (1972-05-01), Burr
patent: 4056925 (1977-11-01), Vogelsberg
patent: 4144700 (1979-03-01), Takai
patent: 4182107 (1980-01-01), Carter et al.
patent: 4328664 (1982-05-01), Vogelsberg
patent: 4377932 (1983-03-01), Dammann et al.
patent: 4427717 (1984-01-01), Gauthier
patent: 4548631 (1985-10-01), Arditty et al.
patent: 5092117 (1992-03-01), Paivinen et al.
patent: 5298047 (1994-03-01), Hart, Jr. et al.
Charbonneau Edward V.
Corning Incorporated
Hoffman John
Wayland Randall S.
LandOfFree
Method for providing controlled spin in optical fiber does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for providing controlled spin in optical fiber, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for providing controlled spin in optical fiber will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3044401