Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-06-28
2003-12-09
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
C385S010000
Reexamination Certificate
active
06661953
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to wavelength division multiplexers and de-multiplexers in optical communications networks and systems. More particularly, the present invention relates to such multiplexers and de-multiplexers that perform the additional functions of detecting and/or variably attenuating the optical power of each signal channel comprising a wavelength division multiplexed composite optical signal.
BACKGROUND OF THE INVENTION
Introduction
Fiber optic communication systems are becoming increasingly popular for data transmission due to their high speed and high data capacity capabilities. A number of very basic optical functions are required to permit the efficient transfer of large amounts of data over such systems and to maintain the operation of the system. Among these basic functions are those of wavelength division multiplexing and demultiplexing. Wavelength division multiplexing permits simultaneous transmission of multiple information-carrying signals, each signal comprising light of a specific restricted wavelength range, along a single optical fiber. A multiplexer combines optical signals of different wavelengths from different paths onto a single combined path; a de-multiplexer separates combined wavelengths input from a single path onto multiple respective paths. Such wavelength combination and separation must occur to allow for the exchange of signals between loops within optical communications networks and to ultimately route each signal from its source to its ultimate destination.
Another basic function needed by fiber optic communication systems is that of independent control of the power levels of all signals comprising a wavelength division multiplexed optical transmission. Because of the power level expectations of receiver equipment within a fiber optic communication systems, all channels must be of a uniform power level. No channel can be significantly more intense than others. However, because of general non-uniform amplification by optical amplifiers and different routes traced by the various channels, re-balancing the channel powers is frequently required at various points. A variable optical attenuator (VOA) is an apparatus that performs this function. A VOA must be capable of simultaneously attenuating the power level of each one of a plurality of channels in a continuous fashion. Conventional means of balancing the channel powers in a wavelength division multiplexed system comprise de-multiplexing the channels, utilizing a separate VOA for each channel and then re-multiplexing the channels.
Another basic function needed by fiber optic communication systems is that of independent detection of power levels of all signals comprising a wavelength division multiplexed optical transmission. Such optical detection and related channel monitoring capabilities are necessary to locate network faults, determine signal quality, detect changes in the performance levels of various items of network equipment, such as light sources, and to control channel power balancing operations of VOA's.
Although various types of (de-)multiplexers, variable optical attenuators and multichannel detection systems are utilized within fiber optic communication systems, there does not currently exist any integrated apparatus which can perform all such functions simultaneously.
Glossary
In this specification, the individual information-carrying lights are referred to as either “signals” or “channels.” The totality of multiple combined signals in a wavelength-division multiplexed optical fiber, optical line or optical system, wherein each signal is of a different wavelength range, is herein referred to as a “composite optical signal.”
The term “wavelength,” denoted by the Greek letter &lgr; (lambda) is used herein synonymously with the terms “signal” or “channel,” except when it is used in the expression “physical wavelength”, where it retains its usual meaning. Although each information-carrying channel actually comprises 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 &lgr;
1
-&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 wavelengths centered at the particular wavelength, &lgr;.”
Strictly speaking, a multiplexer is an apparatus which combines separate channels into a single wavelength division multiplexed composite optical signal and a de-multiplexer is an apparatus that separates a composite optical signal into its component channels. However, since many multiplexers and de-multiplexers ordinarily operate in either sense, the single term “multiplexer” is usually utilized to described either type of apparatus. Although this liberal usage of the term “multiplexer” is generally used in this document, the exact operation—either as a multiplexer or a de-multiplexer—of any particular apparatus should be clear from its respective discussion.
Accordingly, there exists a need for an integrated multifunctional apparatus for fiber optic communication systems. The integrated multifunctional apparatus should provide a combination of demultiplexing/multiplexing, variable optical attenuation, and/or multichannel detection functions simultaneously. The present invention addresses such a need.
SUMMARY OF THE INVENTION
An integrated multifunctional apparatus for fiber optic communication systems includes: at least one input fiber; a lens optically coupled to the at least one input fiber; a diffraction grating optically coupled to the lens at a side opposite to the at least one input fiber; at least one output fiber optically coupled to the lens at the side opposite to the diffraction grating; and a plurality of movable rods residing at the side of the lens opposite to the diffraction grating, where the plurality of movable rods is capable of intercepting a variable portion of a light traversing through the lens. Optionally, the apparatus further comprises a plurality of detectors disposed such that light reflected or scattered by the moveable rods is incident upon the detectors. The apparatus is capable of simultaneously performing the functions of multiplexing or de-multiplexing, variable optical attenuation and/or optical detection of plural channels comprising a wavelength division multiplexed composite optical signal.
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Avanex Corporation
Font Frank G.
Kianni Kaveh C.
Sawyer Law Group LLP
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