Optics: measuring and testing – By light interference
Reexamination Certificate
2003-03-20
2004-04-20
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By light interference
C359S519000
Reexamination Certificate
active
06724482
ABSTRACT:
BACKGROUND INFORMATION
1. Field of the Invention
The present invention relates to the field of fiber optic networks, and more particularly to chromatic dispersion compensators in optical and photonic networks which carry wavelength division multiplexed signals.
2. Description of Related Art
Fiber optic communication systems are becoming increasingly popular for data transmission due to their high speed and high data capacity capabilities. Wavelength division multiplexing is used in such fiber optic communication systems to transfer a relatively large amount of data at a high speed. In wavelength division multiplexing, multiple information-carrying signals, each signal having light of a specific restricted wavelength range, may be transmitted along the same optical fiber.
Each individual information-carrying light is referred to as either “signal” or “channel”. The totality of multiple combined signals in a wavelength-division multiplexed optical fiber, optical line, or optical system, where each signal is of a different wavelength range, is referred to as a “composite optical signal”.
The term “wavelength”, denoted by the Greek letter &lgr; (lambda) is used synonymously with the terms “signal” or “channel”. Although each information-carrying channel may include light of a certain range of physical wavelengths, for simplicity, a single channel is referred to as a single wavelength, &lgr;, and a plurality of n such channels are referred to as “n wavelengths” denoted as &lgr;
1
, &lgr;
2
, . . . &lgr;
n
. Used in this sense, the term “wavelength” may be understood to refer to “the channel nominally comprised of light of a range of physical wavelength centered at the particular wavelength &lgr;”.
Chromatic dispersion is a common well-know problems in high-speed transmission of optical signals. Chromatic dispersion refers to the effect where the various physical wavelengths having an individual channel either travel through an optical fiber or component at different speeds—for instance, longer wavelengths travel faster than shorter wavelengths, or vice versa—or else travel different length paths through a component. This particular problem becomes more acute for data transmission speeds higher than 2.5 gigabytes per second. The resulting pulses of the signal will be stretched, will possibly overlap, and will cause increased difficulty for optical receivers to distinguish where one pulse begins and another ends. This effect seriously compromises the integrity of a signal. Therefore, for fiber optic communication system that provides a high transmission capacity, the system must be equipped to compensate for chromatic dispersion.
Conventional techniques in dealing with chromatic dispersion compensation have been proposed or implemented, such as spectral shaping, interferometers, negative dispersion fiber, and spectral inversion. The objective is to make longer wavelengths travel faster, or make shorter wavelengths travel slower, so that a composite optical signal arrives to a receiver location at the same time. It is also known that Gires-Tournois interferometers (GT cavity) can be used for dispersion compensation. However, a significant shortcoming in GT cavity is that the compensation bandwidth is too narrow for real applications.
Accordingly, there is a need to have a system and method for synthesis of dispersion compensation utilizing GT cavities, which synthesizes any desired compensation functions and provides dispersion compensators on demand.
SUMMARY OF THE INVENTION
The invention provides dispersion compensation systems and methods formed by cascading a series of GT cavities for compensating different chromatic dispersion. In one aspect of the invention, the GT cavities can synthesize any shape of combined dispersion compensation, including positive, negative, and slope dispersion compensation. In another aspect of the invention, the GT cavities are tunable or dynamic to accommodate various types of dispersion compensation. Advantageously, the present invention provides an effective cost solution for easy dispersion compensation tuning.
Other structures and methods are disclosed in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.
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Avanex Corporation
Font Frank G.
Lyons Michael A.
Wilson Sonsini Goodrich & Rosati
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