Method and arrangement for measuring the signal quality in an optical transmission system
View Patent ↗A received binary signal (BS) is sampled with different thresholds, the sampling results are integrated and stored. The measured probability distributions or probability density distributions can be used to draw conclusions concerning the signal quality (for example, the bit error rate) and to optimize the system.
1. A method of measuring a distribution function for determining a signal quality in optical transmission systems, comprising the steps of:
sampling an optical binary signal in a working channel with a first threshold value, producing first sampling values;
additionally sampling said optical binary signal in a measuring channel with a second threshold value during a plurality of measuring intervals in which in each case said second threshold value is varied, producing second sampling values;
comparing respective said first sampling values with said second sampling values, producing comparison values;
integrating or summating said comparison values to produce, for each measuring interval, a summated comparison value;
storing said summated comparison values;
determining a distribution function of said comparison values as a function of said second variable threshold value after an adequate number of said measuring intervals; and
improving said signal quality or optimizing said optical transmission system utilizing said distribution function.
2. A method of measuring a distribution function for determining a signal quality in optical transmission systems, comprising the steps of:
sampling an optical binary signal in a working channel with a first threshold value, producing first sampling values;
additionally sampling said optical binary signal in a measuring channel with a second threshold value during a plurality of measuring intervals in which in each case said second threshold value is varied, producing second sampling values;
additionally sampling said optical binary signal in a measuring channel with a second threshold value during a plurality of measuring intervals in which in each case said second threshold value is varied, producing second sampling values;
determining, for each said measuring interval, a first summated value in said measuring channel by integrating sampled logical zeros or ones;
storing said first summated values;
determining, for each measuring interval, a number of bits received as a summated bit value;
storing said summated bit values;
determining a probability function, after an adequate number of said measuring intervals, as a function of said variable second threshold value for an occurrence of a binary state from said stored first summated values and associated said summated bit values; and
improving said signal quality or optimizing said optical transmission system utilizing said distribution function.
3. A method of measuring a distribution function for determining a signal quality in optical transmission systems, comprising the steps of:
sampling an optical binary signal in a working channel with a first threshold value, producing first sampling values;
additionally sampling said optical binary signal in a measuring channel with a second threshold value during a plurality of measuring intervals in which in each case said second threshold value is varied, producing second sampling values;
determining, for each said measuring interval, a first summated value in said measuring channel by integrating sampled logical zeros or ones;
storing said first summated values;
determining, for each measuring interval, a second summated value in said working channel by integrating received zeros or ones;
storing said second summated values;
determining a probability function, after an adequate number of said measuring intervals, as a function of said variable second threshold value for an occurrence of a binary state from said stored first summated values and associated said second summated values; and
improving said signal quality or optimizing said optical transmission system utilizing said distribution function.
4. The method as claimed in claim 3 , further comprising the steps of:
forming, after each measuring interval, a difference value between said first summated value determined in said measuring channel, and said second summated value determined in the working channel;
storing said difference values for said measuring intervals; and
determining, from said difference values, a probability function for and occurrence of logical sampled values.
5. The method as claimed in claim 4 , further comprising the step of:
determining a probability distribution for an occurrence of logical sampled values that considers said second summated values in the working channel or said summated value of the bits respectively assessed during a measuring interval.
6. The method as claimed in claim 1 , wherein measuring intervals of different lengths are used.
7. The method as claimed in claim 1 , wherein said sampling is synchronous.
8. The method as claimed in claim 1 , wherein said sampling takes place in parallel in a plurality of measuring channels with different threshold values.
9. The method as claimed in claim 8 , wherein said sampling takes place in parallel in a plurality of measuring channels with different threshold values during only one measuring interval.
10. The method as claimed in claim 1 , further comprising the step of changing a sampling instant in the measuring channel after each measuring interval.
11. The method as claimed in claim 1 , further comprising the steps of:
measuring probability distributions with differently set dispersion values; storing measurement results; and
obtaining, from said stored measurement results, an at least approximately optimum value for dispersion compensation.
12. The method as claimed in claim 1 , further comprising the steps of:
determining a probability density distribution; and
deriving criteria for an assessment or optimization of signal quality are derived from said probability density distribution.
13. The method as claimed in claim 2 , wherein measuring intervals of different lengths are used.
14. The method as claimed in claim 3 , wherein measuring intervals of different lengths are used.
15. The method as claimed in claim 2 , wherein said sampling is synchronous.
16. The method as claimed in claim 3 , wherein said sampling is synchronous.
17. The method as claimed in claim 2 , wherein said sampling takes place in parallel in a plurality of measuring channels with different threshold values.
18. The method as claimed in claim 3 , wherein said sampling takes place in parallel in a plurality of measuring channels with different threshold values.
19. The method as claimed in claim 17 , wherein said sampling takes place in parallel in a plurality of measuring channels with different threshold values during only one measuring interval.
20. The method as claimed in claim 18 , wherein said sampling takes place in parallel in a plurality of measuring channels with different threshold values during only one measuring interval.
21. The method as claimed in claim 2 , further comprising the step of changing a sampling instant in the measuring channel after each measuring interval.
22. The method as claimed in claim 3 , further comprising the step of changing a sampling instant in the measuring channel after each measuring interval.
23. The method as claimed in claim 2 , further comprising the steps of: measuring probability distributions with differently set dispersion values; storing measurement results; and
obtaining, from said stored measurement results, an at least approximately optimum value for dispersion compensation.
24. The method as claimed in claim 3 , further comprising the steps of: measuring probability distributions with differently set dispersion values; storing measurement results; and
obtaining, from said stored measurement results, an at least approximately optimum value for dispersion compensation.
25. The method as claimed in claim 2 , further comprising the steps of: determining a probability density distribution; and
deriving criteria for an assessment or optimization of signal quality are derived from said probability density distribution.
26. The method as claimed in claim 3 , further comprising the steps of:
determining a probability density distribution; and
deriving criteria for an assessment or optimization of signal quality are derived from said probability density distribution.