Method for determining signal quality in optical transmission systems

• US 7,116,454 B2
• Filed: 03/11/2002
• Issued: 10/03/2006
• Est. Priority Date: 03/09/2001
• Status: Expired due to Fees

• Current Assignee: Xieon Networks S.A.R.L. (Infinera Corp.)
• Original Assignee: Siemens AG
• Inventors: Elbers, Joerg Peter, Scheerer, Christian, Faerbert, Andreas, Glingener, Christoph
• Primary Examiner(s): Vanderpuye, Kenneth
• Assistant Examiner(s): MALKOWSKI, KENNETH J
• Application Number:
  US10/095,890
• Publication Number:
  US 20030011835A1
• Time in Patent Office: 1,667 Days
• Field of Search: 398/26, 398/25, 398/27
• US Class Current: 398/25
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q

Abstract

A method for determining signal quality in optical transmission systems, wherein the effective signal-to-noise ratio is determined by measuring amplitude histograms of a signal and by calculating characteristic histogram moments and additional interference is ascertained by comparing the characteristic histogram moments with the optical signal-to-noise ratio.

Claims

1. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal, the method comprising the steps of:

calculating characteristic histogram moments from the measured amplitude histogram;

measuring directly an optical signal-to noise ratio from the signal;

comparing the characteristic histogram moments with the measured optical signal-to-noise ratio; and

determining, a proportion of non-linear noise if the comparison yields non-correspondence, wherein a relationship between the characteristic histogram moments and signal-to-noise ratio is determined using the following;

$101<br><br>g<br><br>\left(\frac{{\mathrm{\mu <br><br>}}_1-{\mathrm{\mu <br><br>}}_0}{{\mathrm{\sigma <br><br>}}_1^2-{\mathrm{\sigma <br><br>}}_0^2}\right)=101<br><br>g<br><br>\left(O<br><br><br><br>S<br><br><br><br>N<br><br><br><br>R\right)-101<br><br>g<br><br>\left(\frac{2<br><br>\mathrm{ℛ<br><br>}<br><br>{\langle <br><br>P\rangle <br><br>}_{a<br><br><br><br>v}<br><br>B_{e<br><br><br><br>l}}{B_{o<br><br><br><br>p<br><br><br><br>t}^{O<br><br><br><br>S<br><br><br><br>\mathrm{NR}}}\right)$ $o<br><br><br><br>r<br><br>\left(\frac{{\mathrm{\mu <br><br>}}_1-{\mathrm{\mu <br><br>}}_0}{{\mathrm{\sigma <br><br>}}_1^2-{\mathrm{\sigma <br><br>}}_0^2}\right)=\left(O<br><br><br><br>S<br><br><br><br>N<br><br><br><br>R\right)/\left(\frac{2<br><br>\mathrm{ℛ<br><br>}<br><br>{\langle <br><br>P\rangle <br><br>}_{a<br><br><br><br>v}<br><br>B_{e<br><br><br><br>l}}{B_{o<br><br><br><br>p<br><br><br><br>t}^{O<br><br><br><br>S<br><br><br><br>\mathrm{NR}}}\right).$

where μ

₀ and μ

₁ are average values of the amplitude distribution of the logic “

1'"'"'s” and

“

0'"'"'s”

, σ

₀ and σ

₁ are standard deviations of the amplitude distribution of the logic “

1'"'"'s” and

“

0'"'"'s”

, OSNR is signal-to-noise ratio, <

P>

_av is an average signal power,

$B_{o<br><br><br><br>p<br><br><br><br>t}^{O<br><br><br><br>S<br><br><br><br>N<br><br><br><br>R}$

is an optical bandwidth, B_el is an electrical bandwidth of a photodiode or an opto-electrical transducer, and =η

q/hv is detector sensitivity (η

=quantum efficiency, q=elementary charge, h=quantum of action, v=frequency of the signal).

2. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 1, the method further comprising the steps of:

determining a difference between the average values of the amplitude distributions regarded as Gaussian distribution for logic “

1'"'"'s” and

logic “

0'"'"'s”

;

determining a difference between variances of the amplitude distributions for logic “

1'"'"'s” and

logic “

0'"'"'s”

; and

determining a histogram moments term by forming a quotient from the two differences.

3. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 1, wherein, as the amplitude histogram, measurement is made of one of an error rate distribution in dependence on a variable sampling threshold, or a distribution density of logic “

0'"'"'s”

or logic “

1'"'"'s”

in dependence on the variable sampling threshold, or a probability density distribution of sampling amplitudes of logic “

0'"'"'s and logic “

1'"'"'s,” and

wherein the characteristic histogram values are respectively determined in each case.

4. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 1, wherein the corresponding histogram moments are calculated in dependence on a signal-to-noise ratio of a transmission system having no link interference influences.

5. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 1, wherein the corresponding histogram moments are calculated in dependence on a signal-to-noise ratio without link interference influences for an optimum system.

6. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 3, wherein the corresponding histogram moments and associated signal-to-noise ratios are stored.

7. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 4, wherein the corresponding histogram moments and associated signal-to-noise ratios are stored.

8. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 2, wherein a function of the corresponding histogram moments is stored in dependence on the signal-to-noise ratio.

9. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 3, wherein a function of the corresponding histogram moments is stored in dependence on the signal-to-noise ratio.

10. A method for determining signal quality in optical transmission systems by measuring an amplitude histogram of a signal as claimed in claim 1, wherein the term

$\left(\frac{2\; <li></li>\mathrm{ℛ<br><br>}<br><br>{\langle <br><br>P\rangle <br><br>}_{a<br><br><br><br>v}<br><br>B_{e<br><br><br><br>l}}{B_{o<br><br><br><br>p<br><br><br><br>t}^{O<br><br><br><br>S<br><br><br><br>\mathrm{NR}}}\right)$

is determined by measurement.