Decision threshold adjustment

• US 9,929,802 B2
• Filed: 06/15/2015
• Issued: 03/27/2018
• Est. Priority Date: 06/15/2015
• Status: Active Grant

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Finisar Corporation (II-VI Incorporated)
• Inventors: Lipkin, Ziv
• Primary Examiner(s): Li, Shi K
• Application Number:
  US14/740,010
• Publication Number:
  US 20160365922A1
• Time in Patent Office: 1,016 Days
• CPC Class Codes: H04B 10/07957 Monitoring or measuring wavelength
• CPC Class Codes: H04B 10/695 Arrangements for optimizing the decision element in the receiver, e.g. by using automatic threshold control
• CPC Class Codes: H04B 3/487 Testing crosstalk effects
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation

Abstract

According to an aspect of an embodiment, a method may include receiving a digital data signal at an optical receiver. The method may further include measuring an eye quality of the received digital data signal. In addition, the method may include adjusting a decision threshold of the optical receiver based on the measured eye quality.

Claims

1. A method comprising:

receiving a digital data signal at an optical receiver;

recovering a clock signal from the digital data signal;

measuring an eye quality of the received digital data signal by an eye quality monitor that is driven based on the recovered clock signal;

adjusting a decision threshold value of a decision threshold controller of the optical receiver based on the measured eye quality;

comparing the adjusted decision threshold value against the digital data signal to determine whether to output a digital “

HIGH”

value for the digital data signal or to output a digital “

LOW”

value for the digital data signal;

obtaining a plurality of signal quality factors that include;

a temperature of the optical receiver, a power of an optical signal received at the optical receiver and that includes the digital data signal, a bit rate of the digital data signal, and a channel frequency of the optical signal, wherein the obtaining of each of the signal quality factors is based on the eye quality being affected by the signal quality factors;

detecting a change in the plurality of signal quality factors based on the obtained signal quality factors;

generating an eye quality measurement control signal in response to detecting the change;

activating the eye quality monitor based on the eye quality measurement control signal such that the eye quality monitor takes a subsequent measurement of the eye quality of the digital data signal in response to the change being detected;

analyzing the subsequent measurement of the eye quality in response to detecting the change; and

readjusting the decision threshold value based on the analyzing of the subsequent measurement of the eye quality that was made in response to the eye quality measurement control signal that was generated in response to detecting the change.

2. The method of claim 1, further comprising:

measuring the eye quality of the digital data signal with respect to a plurality of decision threshold value levels;

determining a best eye quality with respect to the plurality of decision threshold value levels;

determining a best decision threshold value level of the plurality of decision threshold value levels that corresponds to the determined best eye quality; and

adjusting, based on the determined best decision threshold value, the decision threshold value such that its level is at least approximately equal to the determined best decision threshold value.

3. The method of claim 2, wherein determining the best eye quality includes determining one or more of the following:

a largest overall eye opening, a largest eye margin, a largest percentage of eye opening, a largest internal eye height, a largest eye amplitude, a largest eye crossing, a largest eye quality factor, a largest vertical eye opening, a largest eye width, and a largest horizontal eye opening.

4. The method of claim 1, further comprising:

comparing the measured eye quality with a quality threshold; and

adjusting the decision threshold in response to the comparing indicating that the measured eye quality does not satisfy the quality threshold.

5. The method of claim 4, further comprising repeating measuring the eye quality and adjusting the decision threshold until the eye quality satisfies the quality threshold.

6. The method of claim 4, wherein the quality threshold includes one or more of the following:

an overall eye opening threshold, an eye margin threshold, a percentage of eye opening threshold, an internal eye height threshold, an eye amplitude threshold, an eye crossing threshold, an eye quality factor threshold, a vertical eye opening threshold, an eye width threshold, and a horizontal eye opening threshold.

7. The method of claim 1, further comprising:

performing a first eye quality measurement with respect to the decision threshold being at a first level;

adjusting the decision threshold to a second level;

performing a second eye quality measurement with respect to the decision threshold being at the second level;

determining that the digital data signal has a better quality with the decision threshold at the first level as opposed to the second level based on the first eye quality measurement and the second eye quality measurement; and

adjusting the decision threshold back to the first level in response to determining that the digital data signal has a better quality with the decision threshold at the first level as opposed to the second level.

8. A system comprising:

an optical receiver configured to;

receive an optical signal that includes a digital data signal; and

convert the optical signal into an electrical signal that includes the digital data signal;

an eye quality monitor communicatively coupled to the optical receiver and configured to;

receive the electrical signal; and

measure an eye quality of the digital data signal included in the electrical signal; and

a control system communicatively coupled to the optical receiver and the eye quality monitor and configured to;

adjust a decision threshold value of a decision threshold controller of the optical receiver based on the eye quality measured by the eye quality monitor, the decision threshold value being compared against the electrical signal to determine whether to output a digital “

HIGH”

value for the digital data signal or to output a digital “

LOW”

value for the digital data signal;

detect a change in two or more of the following;

a temperature of the optical receiver, a power of an optical signal that includes the digital data signal, a bit rate of the digital data signal, and a channel frequency of the optical signal;

generate an eye quality measurement control signal in response to detecting the change;

communicate the eye quality measurement control signal to the eye quality monitor such that the eye quality monitor is activated to take a subsequent measurement of the eye quality of the digital data signal in response to the change being detected;

obtain, from the eye quality monitor, the subsequent measurement of the eye quality;

analyze the subsequent measurement of the eye quality in response to detecting the change; and

readjust the decision threshold value based on the analyzing of the subsequent measurement of the eye quality that was measured in response to the eye quality measurement control signal that was generated in response to detecting the change.

9. The system of claim 8, wherein:

the eye quality monitor is further configured to measure the eye quality of the digital data signal with respect to a plurality of decision threshold value levels; and

the control system is further configured to;

determine a best eye quality with respect to the plurality of decision threshold value levels;

determine a best decision threshold value level of the plurality of decision threshold value levels that corresponds to the determined best eye quality; and

adjust, based on the determined best decision threshold value, the decision threshold value such that its level is at least approximately equal to the determined best decision threshold value.

10. The system of claim 9, wherein determining the best eye quality includes determining one or more of the following:

a largest overall eye opening, a largest eye margin, a largest percentage of eye opening, a largest internal eye height, a largest eye amplitude, a largest eye crossing, a largest eye quality factor, a largest vertical eye opening, a largest eye width, and a largest horizontal eye opening.

11. The system of claim 8, wherein the control system is further configured to:

compare the measured eye quality with a quality threshold; and

adjust the decision threshold in response to the comparing indicating that the measured eye quality does not satisfy the quality threshold.

12. The system of claim 11, wherein:

the eye quality monitor is further configured to repeat measuring the eye quality; and

the control system is further configured to adjust the decision threshold until the eye quality satisfies the quality threshold.

13. The system of claim 11, wherein the quality threshold includes one or more of the following:

an overall eye opening threshold, an eye margin threshold, a percentage of eye opening threshold, an internal eye height threshold, an eye amplitude threshold, an eye crossing threshold, an eye quality factor threshold, a vertical eye opening threshold, an eye width threshold, and a horizontal eye opening threshold.

14. The system of claim 8, wherein:

the eye quality monitor is further configured to perform a first eye quality measurement with respect to the decision threshold being at a first level;

the control system is further configured to adjust the decision threshold to a second level;

the eye quality monitor is further configured to perform a second eye quality measurement with respect to the decision threshold being at the second level; and

the control system is further configured to;

determine that the digital data signal has a better quality with the decision threshold at the first level as opposed to the second level based on the first eye quality measurement and the second eye quality measurement; and

adjust the decision threshold back to the first level in response to determining that the digital data signal has a better quality with the decision threshold at the first level as opposed to the second level.

15. One or more processors configured to cause a system to perform operations, the operations comprising:

detecting a change in three or more of the following;

a temperature of an optical receiver, a power of an optical signal received at the optical receiver and that includes a digital data signal, a bit rate of the digital data signal, and a channel frequency of the optical signal;

generating an eye quality measurement control signal in response to detecting the change;

communicating the eye quality measurement control signal to an eye quality monitor such that the eye quality monitor is activated to take a measurement of an eye quality of the digital data signal in response to the change being detected;

obtaining, from the eye quality monitor, the measurement of the eye quality;

analyzing the measurement of the eye quality of the digital data signal in response to detecting the change; and

adjusting a decision threshold value, which is compared against the digital data signal, of the optical receiver based on the analyzing of the measurement of the eye quality that was made in response to the eye quality measurement control signal that was generated in response to detecting the change.

16. The one or more processors of claim 15, wherein the operations further comprise:

analyzing the eye quality of the digital data signal with respect to a plurality of decision threshold value levels;

determining a best eye quality with respect to the plurality of decision threshold value levels;

determining a best decision threshold value level of the plurality of decision threshold value levels that corresponds to the determined best eye quality; and

adjusting, based on the determined best decision threshold value, the decision threshold value such that its level is at least approximately equal to the determined best decision threshold value.

17. The one or more processors of claim 15, wherein the operations further comprise:

comparing the measured eye quality with a quality threshold; and

adjusting the decision threshold in response to the comparing indicating that the measured eye quality does not satisfy the quality threshold.

18. The one or more processors of claim 15, wherein the operations further comprise:

analyzing a first eye quality measurement with respect to the decision threshold being at a first level;

adjusting the decision threshold to a second level;

analyzing a second eye quality measurement with respect to the decision threshold being at the second level;

determining that the digital data signal has a better quality with the decision threshold at the first level as opposed to the second level based on the first eye quality measurement and the second eye quality measurement; and

adjusting the decision threshold back to the first level in response to determining that the digital data signal has a better quality with the decision threshold at the first level as opposed to the second level.