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Polarisation mode dispersion compensator and self-adapting regulation method thereof

An adaptive adjustment and compensator technology, applied in instruments, optical components, optics, etc., to solve problems such as optical signal distortion and dispersion

Inactive Publication Date: 2007-04-25
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] PMD is known to distort and disperse optical signals transmitted over fiber optic connections

Method used

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  • Polarisation mode dispersion compensator and self-adapting regulation method thereof
  • Polarisation mode dispersion compensator and self-adapting regulation method thereof
  • Polarisation mode dispersion compensator and self-adapting regulation method thereof

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Embodiment Construction

[0060] Referring to the accompanying drawings, FIG. 1 shows the structure of a PMD compensator identified by the numeral 10 as a whole. The structure consists of several cascaded optics to receive the signal from the transmission fiber 11 . The first optical device is a polarization controller 12 (PC), which allows modification of the polarization state of the optical signal at its input. Therefore, three polarization maintaining fibers 13 (PMF) separated by two optical rotators 14 are provided.

[0061] A PMF fiber is a fiber that can introduce a predetermined differential group delay (DGD) between the two principal states of polarization (PSP), ie, the slow PSP and fast PSP components, of an optical signal.

[0062] As far as the compensator shown in Figure 1 is concerned, the DGD delays on the optical carrier frequency introduced by the three PMFs are respectively τ c , ατ c and (1-α)τ c , where, 0c and α are design parameters.

[0063] The optical rotator can change t...

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PUM

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Abstract

A method for the adaptive adjustment of a PMD compensator in optical fiber communication systems comprises the steps of taking the signal at the compensator output and extracting the components y1(t) and y2(t) on the two orthogonal polarizations, computing the signal y(t)=[y1(t)]2+[y2(t)]2, sampling the signal y(t) at instants tk=kT with T=symbol interval to obtain samples y(tk), computing the mean square error e(k)=y(tk)-u(k) with u(k) equal to the symbol transmitted, and adjusting the parameters of the compensator to seek to minimize e(k). A PMD compensator in accordance with the method comprises an adjustment system which comprises in turn a photodetecor ( 17 ) which takes the components y1(t) and y2(t) on the two orthogonal polarizations from the signal at the compensator output, a sampler ( 19 ) which samples at instants tk=kT with T=symbol interval, the signal y(t)=[y1(t)]2+[y2(t)]2 at the output of the photodetector ( 17 ) to obtain samples y(tk), a circuit ( 18, 20 ) for computation of the mean square error e(k)=y(tk)-u(k) with u(k) equal to the symbol transmitted, and a regulator ( 15, 16 ) which regulates the parameters of the compensator to seek to minimize e(k).

Description

technical field [0001] The invention relates to a method for adaptively adjusting a polarization mode dispersion (PMD) compensator in an optical fiber communication system. The invention also relates to a compensator applying said method. Background technique [0002] It is well known that in optical fiber communication equipment it is necessary to compensate for the PMD effect that occurs when optical signals propagate in optical fiber connections. [0003] PMD is known to distort and disperse optical signals transmitted over fiber optic connections. The different time delays between the various signal components in different polarization states become increasingly important as the transmission speed increases. In modern optical fiber transmission systems at very high frequencies (10 Gbit / s and above), accurate compensation of the PDM effect becomes important but tricky. This compensation must be dynamic and performed at sufficient speed. [0004] The main object of the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B10/18G02B6/34H04B10/2569
CPCH04B10/2569G02B6/278G02B6/4215G02B6/2713G02B6/274G02B6/29395
Inventor G·普拉蒂E·福雷斯蒂里G·科拉沃尔佩
Owner TELEFON AB LM ERICSSON (PUBL)