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Method and apparatus for two-port allpass compensation of polarization mode dispersion

A polarization mode dispersion and compensator technology, applied in the coupling of optical waveguides, electrical components, electromagnetic wave transmission systems, etc., can solve problems such as polarization mode dispersion

Inactive Publication Date: 2005-08-17
LUCENT TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Wavelength-dependent coupling between modes then leads to polarization mode dispersion, which becomes the main limiting factor for transmission rate as bandwidth increases

Method used

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  • Method and apparatus for two-port allpass compensation of polarization mode dispersion
  • Method and apparatus for two-port allpass compensation of polarization mode dispersion
  • Method and apparatus for two-port allpass compensation of polarization mode dispersion

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Embodiment Construction

[0013] The present invention provides a method and apparatus to compensate for polarization mode dispersion by cascading an all-pass filter with a directional coupler. The disclosed PMD compensator adjusts the coefficients of an adaptive filter structure including an all-pass filter and a directional coupler based on a minimized cost function. Initially, the phase and magnitude of the polarization components are evaluated to characterize the channel's PMD and adjust the tunable PMD compensator. Fig. 1 is the schematic block diagram of a conventional optical receiver 100, and this optical receiver has adopted a PMD compensator 400, and this will be hereinafter with Figure 4 discuss together. Generally, the PMD compensator 400 employs a PMD measurement device 300 to measure PMD, and an adaptive optical filter 110 to compensate the measured PMD, which will be discussed below with FIG. 3 . The PMD compensator 400 may be integrated with the optical receiver 100 or may be located ...

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Abstract

A method and apparatus are disclosed for compensating for polarization mode dispersion using cascaded all-pass filters and directional couplers. The disclosed PMD compensator adjusts the coefficients of an adaptive filter structure involving all-pass filters and directional couplers based on a minimized cost function. In one implementation, a stochastic gradient algorithm, also referred to as the least mean square algorithm, is employed to sequentially reduce the value of the cost function by the method of steepest descent. In one another implementation, convergence is improved by employing a Newton algorithm that uses second derivatives to accelerate convergence.

Description

technical field [0001] The present invention relates generally to fiber optic transmission systems, and more particularly to methods and apparatus for measuring and controlling polarization mode dispersion (PMD) in such fiber optic transmission systems. Background technique [0002] Optical communication systems increasingly adopt wavelength division multiplexing (WDM) technology to transmit multiple information signals with different optical frequencies in the same optical fiber. WDM technology is being used to meet the growing demand for increased speed and bandwidth in optical transmission applications, including fiber optic communication systems. [0003] Polarization Mode Dispersion (PMD) is a fundamental issue limiting channel capacity in single-mode fiber optic communication systems. The asymmetry of the fiber produces random birefringence effects, which lead to differential group delay (DGD) between the two main polarization modes. The wavelength-dependent coupling...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B6/26H04B10/12H04B10/18
CPCH04B10/2569
Inventor 丹尼斯·R.·摩根
Owner LUCENT TECH INC