Optical equalization
AssigneeLucent Technologies Inc.
InventorsDouglas Gill, Xiang Liu
Life of this patent
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Abstract
A device and method for processing a signal e.g. equalizing a signal, is disclosed. Such processing involves dividing a signal into two portions that each traverses a wavepath and then are combined. The respective wavepaths impose a non-linear frequency-versus-phase dependency on a signal portion. The frequency-versus-phase dependencies that characterize the respective wavepaths are similar in shape but inverted from each other. A processed signal has significantly improved signal-to-noise ratio.
Claims11
A method for processing a signal that is transmitted over an optical wavelength range encompassed by a channel of an optical communications system, said method comprising the steps of 1) coupling a first and second portion of said signal into a device wherein said first portion traverses a first optical wavepath of said device and said second portion traverses a second wavepath of said device, and 2) combining said first portion and second portion after said traversing of said first and second wavepath respectively characterized in that a first frequency-versus-phase dependency is imposed on said first portion by said first wavepath and a second frequency-versus-phase dependency is imposed on said second portion by said second wavepath such that said dependencies induce a signal group delay on said signal portions having a magnitude exceeding 200 BR−2 ps/GHz for at least one wavelength within said channel of said signal where BR is the signal bit rate divided by 109 symbols/sec and wherein said first and second frequency-versus-phase dependency and said frequency-versus-phase dependency are similar to and inverted from each other.
An equalizer comprising an input optical wavepath, a first coupler between a first and second wavepath, said first coupler configured to divide an input signal into a first portion traversing said first wavepath and a second portion traversing said second wavepath and a second coupler configured to couple said first portion and said second portion after said first portion traverses said first wavepath and said second portion traverses said second wavepath wherein said signal encompasses a wavelength range of a communication channel characterized in that said first wavepath is configured to impose a first frequency-versus-phase dependency on said first portion and said second wavepath is configured to impose a second frequency-versus-phase dependency on said second portion such that said first and second dependencies induce on said signal portions a signal group delay exceeding 200 BR−2 ps/GHz for at least one wavelength within said channel wherein BR is the bit rate of said signal divided by 109 symbols/sec and wherein said first frequency-versus-phase dependency and said second frequency-versus-wavelength dependency are similar to and inverted from each other.
Dependencies are inferred from the claim text.