Optical waveguides – Optical fiber waveguide with cladding
Reexamination Certificate
1998-08-20
2001-07-10
Bovernick, Rodney (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
C385S024000, C359S199200, C359S341430
Reexamination Certificate
active
06259845
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed toward optical communication systems incorporating dispersion compensation and particularly such systems having an adjustable amount of dispersion compensation and to components of such systems.
BACKGROUND OF THE INVENTION
Optical signals transmitted in a fiber optic communication system typically constitute a series of pulses of digital information. Although the pulses are usually at a single nominal wavelength, each pulse is actually composed of different spectral components. The spectral components of each pulse propagate through the transmission fiber at different speeds with higher frequency components traveling slower than lower frequency components in non-dispersion shifted optical fiber. This effect, known as “chromatic dispersion”, can result in spectral components of one pulse arriving at a receiver at substantially the same time as a succeeding pulse, thereby causing degraded receiver sensitivity. Chromatic dispersion becomes increasingly pronounced at higher bit rates, e.g. those associated with synchronous optical network (SONET) OC-192 transmission speeds.
Typically, optical signals propagating through transmission optical fiber experience a positive dispersion. Accordingly, dispersion compensated fiber (DCF) having a negative dispersion can be coupled to the transmission optical fiber in order to offset the chromatic dispersion thereof. The amount of dispersion experienced by an optical signal depends on the distance traveled through the transmission optical fiber. Shorter lengths of transmission optical fiber require less compensation than longer lengths. Likewise, longer lengths of DCF are used when more compensation is required, and shorter lengths of DCF are provided when less compensation is needed. Each segment of transmission optical fiber, however, requires a unique length of DCF in order to provide an appropriate amount of dispersion compensation.
In a fiber optic network, many different lengths or spans of transmission optical fiber are used to connect various points within the network. According to the conventional approach to dispersion compensation described above, a unique length of DCF must be cut for each span. If the network contains many spans, a corresponding number of DCF fibers must be provided, each having a different length. As a result, the conventional approach to dispersion compensation in such instances can be inefficient and time consuming.
SUMMARY OF THE INVENTION
Consistent with the present invention, a dispersion compensation module is provided comprising a first optical fiber having a positive dispersion and a second optical fiber having a negative dispersion. One of the first and second optical fibers is configured to be coupled to a transmission optical fiber. The first and second optical fibers are selectively coupled to each other in order that the dispersion compensation module have a desired amount of dispersion to thereby compensate a dispersion associated with the transmission optical fiber.
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Sano, A., et al., “Automatic dispersion equalization by monitoring extracted clock power level in a 40-Gbit/s 200-km transmission line,” 22ndEuropean Conference on Optical Communication ECOC, pp. 207-210, 1996 No month.
Bovernick Rodney
Ciena Corporation
Kim Ellen E.
Soltz David L.
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