Identification level control method and optical receiver

• US 7,382,987 B2
• Filed: 04/12/2004
• Issued: 06/03/2008
• Est. Priority Date: 10/09/2003
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Sato, Tetsuji, Yoshida, Yuko, Misaizu, Setsuo
• Primary Examiner(s): Chan; Jason
• Assistant Examiner(s): CURS, NATHAN M
• Application Number:
  US10/821,853
• Publication Number:
  US 20050078966A1
• Time in Patent Office: 1,513 Days
• Field of Search: 398208-211
• US Class Current: 398/202
• CPC Class Codes: H03F 3/087 with IC amplifier blocks H03F3/085 takes precedence
• CPC Class Codes: H03G 3/3084 in receivers or transmitters for electromagnetic waves other than radiowaves, e.g. lightwaves H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03K 5/082 with an adaptive threshold
• 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: H04L 25/063 Setting decision thresholds using feedback techniques only

Abstract

An identification level control method and an optical receiver are disclosed to determine an optimal identification level in a simple structure without clock extraction. In the identification level control method, an identification level supplied to a limiter amplifier is changed from a lower bound to an upper bound thereof and is stored together with an output average of the limiter amplifier. Then, a first average and a second average are set based on the output average. A first identification level corresponding to the first average and a second identification level corresponding to the second average are obtained, and an optimal identification level is computed based on the first identification level and the second identification level, and is supplied to the limiter amplifier.

Claims

1. A method of controlling an identification level for an optical receiver wherein the optical receiver converts an optical signal from an optical fiber into an electric signal, uses a limiter amplifier to amplify the electric signal, and reproduces data, the method comprising:

changing an identification level supplied to the limiter amplifier between a lower bound and an upper bound thereof and storing a respective average of an output of the limiter amplifier corresponding to each identification level together with the identification level;

setting a first average between a minimal value of the respective averages and a predefined value and a second average between a maximal value of the respective averages and the predefined value, said predefined value being between the minimal value and the maximal value, and obtaining a first identification level corresponding to the first average and a second identification level corresponding to the second average; and

computing an optimal identification level based on the first identification level and the second identification level and supplying the optimal identification level to the limiter amplifier.

2. The method as claimed in claim 1, wherein the first average and the second average are substantially equal to Min +0.25(Max-Min) and Min +0.75(Max-Min), wherein the minimal value and the maximum value are represented by Min and Max, respectively.

3. The method as claimed in claim 1, wherein the optimal identification level is set between (ld1+0.3(ld2−

ld1)) and (ld1+0.4(ld2−

ld1)), wherein the first identification level and the second identification level are represented by ld1 and ld2, respectively.

4. A method of controlling an identification level for an optical receiver wherein the optical receiver converts an optical signal from an optical fiber into an electric signal, uses a limiter amplifier to amplify the electric signal, and reproduces data, the method comprising:

changing an identification level supplied to a monitoring limiter amplifier between a lower bound and an upper bound thereof, said monitoring limiter amplifier receiving the electric signal, and storing a respective average of an output of the monitoring limiter amplifier corresponding to each identification level together with the identification level;

setting a first average between a minimal value of the respective averages and a predefined value and a second average between a maximal value of the respective averages and the predefined value, said predefined value being between the minimal value and the maximal value, and obtaining a first identification level corresponding to the first average and a second identification level corresponding to the second average; and

computing an optimal identification level based on the first identification level and the second identification level and supplying the optimal identification level to the limiter amplifier.

5. The method as claimed in claim 4, wherein the first average and the second average are substantially equal to Min +0.25(Max-Min) and Min +0.75(Max-Min), wherein the minimal value and the maximum value are represented by Min and Max, respectively.

6. The method as claimed in claim 4, wherein the optimal identification level is set between (ld1+0.3(ld2−

ld1)) and (ld1+0.4(ld2−

ld1)), wherein the first identification level and the second identification level are represented by ld1 and ld2, respectively.

7. An optical receiver for converting an optical signal from an optical fiber into an electric signal, using a limiter amplifier to amplify the electric signal, and reproducing data, comprising:

a change part changing an identification level supplied to the limiter amplifier between a lower bound and an upper bound thereof;

a storage part storing a respective average of an output of the limiter amplifier corresponding to each identification level together with the identification level; and

a computation part setting a first average between a minimal value of the respective averages and a predefined value and a second average between a maximal value of the respective averages and the predefined value, said predefined value being between the minimal value and the maximal value, obtaining a first identification level corresponding to the first average and a second identification level corresponding to the second average, computing an optimal identification level based on the first identification level and the second identification level, and supplying the optimal identification level to the limiter amplifier.

8. The optical receiver as claimed in claim 7, wherein the first average and the second average are substantially equal to Min +0.25(Max-Min) and Min +0.75(Max-Min), wherein the minimal value and the maximum value are represented by Min and Max, respectively.

9. The optical receiver as claimed in claim 7, wherein the optimal identification level is set between (ld1+0.3(ld2−

ld1)) and (ld1+0.4(ld2−

ld1)), wherein the first identification level and the second identification level are represented by ld1 and ld2, respectively.

10. An optical receiver for converting an optical signal from an optical fiber into an electric signal, using a limiter amplifier to amplify the electric signal, and reproducing data, comprising:

a monitoring limiter amplifier receiving the electric signal;

a change part changing an identification level supplied to the monitoring limiter amplifier between a lower bound and an upper bound thereof;

a storage part storing a respective average of an output of the monitoring limiter amplifier corresponding to each identification level together with the identification level; and

a computation part setting a first average between a minimal value of the respective averages and a predefined value and a second average between a maximal value of the respective averages and the predefined value, said predefined value being between the minimal value and the maximal value, obtaining a first identification level corresponding to the first average and a second identification level corresponding to the second average, computing an optimal identification level based on the first identification level and the second identification level, and supplying the optimal identification level to the limiter amplifier.

11. The optical receiver as claimed in claim 10, wherein the first average and the second average are substantially equal to Min +0.25(Max-Min) and Min +0.75(Max-Min), wherein the minimal value and the maximum value are represented by Min and Max, respectively.

12. The optical receiver as claimed in claim 10, wherein the optimal identification level is set between (ld1+0.3(ld2−

ld1)) and (ld1+0.4(ld2−

ld1)), wherein the first identification level and the second identification level are represented by ld1 and ld2, respectively.