Methods and apparatus for detecting a faulty component location along an optical path in an optical network

• US 20050190359A1
• Filed: 02/25/2005
• Published: 09/01/2005
• Est. Priority Date: 02/26/2004
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Tropic Networks, Inc. (Nokia Corporation)
• Inventors: Wan, Ping Wai, Remedios, Derrick, Bacque, James Benson, Ng, Eddie Kai Ho
• Granted Patent: US 7,139,069 B2
• Time in Patent Office: Days
• US Class Current: 356/73.1
• CPC Class Codes: H04B 10/077 using a supervisory or additional signal
• CPC Class Codes: H04B 10/07955 Monitoring or measuring power

Abstract

A multi-stage method and apparatus for determining a faulty component location along an optical path through an optical fiber in an optical network are disclosed. The optical fiber carries a plurality of wavelengths, which may or may not be modulated by low frequency dither tones that are utilized for identification purposes and performance monitoring in the optical network. First, the method comprises measuring a total power of the optical fiber and a total wavelength power as a sum of powers of the individual wavelengths at a plurality of local detection points; comparing the measured powers at the local detection points; and determining whether or not a faulty detection point exists along the optical path. If a fault is identified, the method further provides a multi-stage fault detection procedure, which comprises measuring a total wavelength power loss between a local detection point and an adjacent detection point, between the local detection point and multiple non-adjacent detection points. A correlation of the measured total wavelength power losses between the various detection points is used for determining the faulty component location along the optical path. The apparatus, which incorporates the above multi-stage method for determining the faulty component location in the optical network, is also provided.

Claims

1. A method for determining a faulty component location along an optical path through an optical fiber in an optical network, the optical fiber carrying a plurality of individual wavelengths, the method comprising the steps of:

(a) measuring a total power of the optical fiber at a plurality of local detection points along the optical path;

(b) measuring a total wavelength power of said individual wavelengths at each of said local detection points;

(c) if a discrepancy between the total power of the optical fiber in step (a) and the total wavelength power in step (b) exceeding an accuracy of measurements is detected at a local detection-point, determining that a faulty detection point or a component may exist along the optical path;

(d) measuring a loss of a total wavelength power between a local detection point and a detection point adjacent to said local detection point; and

(e) for each pair of the local and adjacent detection points, if the loss of the total wavelength power in step (d) is greater than a reference loss value for the respective pair, determining one or more of the following;

a fault occurs at the local detection point,

a fault occurs at the adjacent detection point, and

a faulty component is located between the local detection point and the adjacent detection point to said local detection point.

2. The method as described in claim 1, wherein the individual wavelengths are modulated by a low frequency dither tone for identification purposes and performance monitoring in the optical network, and wherein the step (a) is performed before modulating the wavelengths with the dither tones, and the steps (b) and (d) are performed after modulating the wavelengths with the dither tones.

3. The method as described in claim 1, wherein the step (c) comprises:

(p) computing a difference between the total power of the optical fiber (P_total) and the total wavelength power (P_S) of the individual wavelengths of said optical fiber, wherein the difference (Difference-in-Power) is given by the following formula;

$\begin{array}{c}\mathrm{Difference}<br><br>\text{-}<br><br>\mathrm{in}<br><br>\text{-}<br><br>\mathrm{Power}=P_{\mathrm{total}}-P_S,\mathrm{and}\\ P_S=\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_j,\end{array}$

wherein P_j is an individual wavelength power for a j^th wavelength, and M is a number of wavelengths of said optical fiber; and

(q) if the difference in step (p) is greater than a predetermined value (X) and less than a pre-determined value (Y), determining that a faulty detection point or a component may exist along the optical path.

4. The method as described in claim 3, wherein the pre-determined value (X) is about “

3 dB”

, and the pre-determined value (Y) is about “

−

1 dB”

.

5. The method as described in claim 1, wherein the step (d) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+1}=\left(1/M\right)*\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>\left(P_{k_j}-P_{k+1<br><br>j}\right)$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+1j is a power of the j^th wavelength at the adjacent detection point (k+1), and M is a number of wavelengths of said optical fiber.

6. The method as described in claim 1, wherein the step (d) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+1}=\left(1/M\right)*\left(\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k_j}-\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k+1_j}\right)$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+1j is a power of the j^th wavelength at the adjacent detection point (k+1), and M is a number of wavelengths of said optical fiber.

7. The method as described in claim 5, wherein the step (e) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+1|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+1|_T1−

V), wherein (V) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+1|_T2); and

(u) if the |L_k,k+1|_T2| in step (t) is less than the respective reference loss value (|L_k,k+1|_T1|−

V) in step (s), determining that a faulty component is located between the local detection point and the adjacent detection point.

8. The method as described in claim 7, wherein the pre-determined value (V) is about 1 dB.

9. The method as described in claim 7, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

10. The method as described in claim 7, wherein the step (r) comprises averaging each of the respective (L_k,k+1|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+1|_T2) values over a time interval Δ

T2 preceding T2.

11. The method as described in claim 6, wherein the step (e) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+1|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+1|_T1|−

V), wherein (V) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+1|_T2); and

(u) if the |L_k,k+1|_T2| in step (t) is less than the respective reference loss value (|L_k,k+1|_T1|−

V) in step (s), determining that a faulty component is located between the local detection point and the adjacent detection point.

12. The method as described in claim 11, wherein the pre-determined value (V) is about 1 dB.

13. The method as described in claim 11, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

14. The method as described in claim 11, wherein the step (r) comprises averaging each of the respective (L_k,k+1|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+1|_T2) values over a time interval Δ

T2 preceding T2.

15. The method as described in claim 1, further comprising:

(f) measuring a loss of a total wavelength power between a local detection point and a detection point which is non-adjacent to said local detection point; and

(g) for each pair of the local and non-adjacent detection points, if the loss of the total wavelength power in step (f) is less than a reference loss value for the respective pair, determining one or more of the following;

a faulty component is located between the local detection point and the adjacent detection point, and

a faulty component is located between the local detection point and the non-adjacent detection point.

16. The method as described in claim 15, wherein the step (f) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+i}=\left(1/M\right)*\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>\left(P_{k_j}-P_{k+i_j}\right),$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+ij is a power of the j^th wavelength at the adjacent detection point (k+i), i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path, and M is a number of wavelengths of said optical fiber.

17. The method as described in claim 15, wherein the step (f) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+i}=\left(1/M\right)*\left(\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k_j}-\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k+i_j}\right),$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+ij is a power of the j^th wavelength at the adjacent detection point (k+i), i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path, and M is a number of wavelengths of said optical fiber.

18. The method as described in claim 16, wherein the step (g) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+i|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+i|_T1|−

W), wherein (W) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+i|T2); and

(u) if the |L_k,k+i|_T2| in step (t) is less than the respective reference loss value (|L_k,k+i|_T1|−

W) in step (s), determining that a faulty component is located between the local detection point and the non-adjacent detection point.

19. The method as described in claim 18, wherein the pre-determined value (W) is about 1 dB.

20. The method as described in claim 18, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

21. The method as described in claim 18, wherein the step (r) comprises averaging each of the respective (L_k,k+i|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+i|_T2) values over a time interval Δ

T2 preceding T2, and i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path.

22. The method as described in claim 17, wherein the step (g) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+i|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+i|_T1|−

W), wherein (W) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+i|_T2); and

(u) if the |L_k,k+i|_T2| in step (t) is less than the respective reference loss value (|L_k,k+i|_T1|−

W) in step (s), determining that a faulty component is located between the local detection point and the non-adjacent detection point.

23. The method as described in claim 22, wherein the pre-determined value (W) is about 1 dB.

24. The method as described in claim 22, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

25. The method as described in claim 22, wherein the step (r) comprises averaging each of the respective (L_k,k+i|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+i|_T2) values over a time interval Δ

T2 preceding T2, and i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path.

26. A method for determining a faulty component location along an optical path through an optical fiber in an optical network, the optical fiber carrying a plurality of individual wavelengths, the method comprising the steps of:

(j) measuring a loss of a total wavelength power between a local detection point and a detection point adjacent to said local detection point;

(k) for each pair of the local and adjacent detection points, if the loss of the total wavelength power in step (j) is less than a reference loss value for the respective pair, determining one or more of the following;

a fault occurs at the local detection point,

a fault occurs at the adjacent detection point, and

a faulty component is located between the local detection point and the adjacent detection point;

(l) measuring a loss of a total wavelength power between the local detection point and a detection point, which is non-adjacent to, said local detection point;

(m) for each pair of the local and non-adjacent detection points, if the loss of the total wavelengths power in step (l) is less than a reference loss value for the respective pair, determining one or more of the following;

a fault occurs at the non-adjacent detection point, a faulty component is located between the local detection point and the adjacent detection point, and

a faulty component is located between the local detection point and the non-adjacent detection point.

27. The method as described in claim 26, wherein the individual wavelengths are modulated by a low frequency dither tone for identification purposes and performance monitoring in the optical network, and wherein the steps (j) and (l) are performed after modulating the wavelengths with the dither tones.

28. The method as described in claim 26, wherein the step (j) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+1}=\left(1/M\right)*\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>\left(P_{k_j}-P_{k+1_j}\right),$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+1j is a power of the j^th wavelength at the adjacent detection point (k+1), and M is a number of wavelengths of said optical fiber.

29. The method as described in claim 26, wherein the step (j) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+1}=\left(1/M\right)*\left(\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k_j}-\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k+1_j}\right),$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+1j is a power of the j^th wavelength at the adjacent detection point (k+1), and M is a number of wavelengths of said optical fiber.

30. The method as described in claim 28, wherein the step (k) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+1|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+1|_T1|−

V), wherein (V) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+1|_T2); and

(u) if the |L_k,k+1|_T2| in step (t) is less than the respective reference loss value (|L_k,k+1|_T1|V) in step (s), determining that a faulty component is located between the local detection point and the adjacent detection point.

31. The method as described in claim 30, wherein the pre-determined value (V) is about 1 dB.

32. The method as described in claim 30, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

33. The method as described in claim 30, wherein the step (r) comprises averaging each of the respective (L_k,k+1|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+1|_T2) values over a time interval Δ

T2 preceding T2.

34. The method as described in claim 29, wherein the step (k) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+1|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+1|_T1|−

V), wherein (V) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+1|_T2); and

(u) if the |L_kk+1|_T2| in step (t) is less than the respective reference loss value (|L_k,k+1|_T1|−

V) in step (s), determining that a faulty component is located between the local detection point and the adjacent detection point.

35. The method as described in claim 34, wherein the pre-determined value (V) is about 1 dB.

36. The method as described in claim 34, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

37. The method as described in claim 34, wherein the step (r) comprises averaging each of the respective (L_k,k+1|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+1|_T2) values over a time interval Δ

T2 preceding T2.

38. The method as described in claim 26, wherein the step (l) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+i}=\left(1/M\right)*\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>\left(P_{k_j}-P_{k+i_j}\right),$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+ij is a power of the j^th wavelength at the adjacent detection point (k+i), i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path, and M is a number of wavelengths of said optical fiber.

39. The method as described in claim 26, wherein the step (l) comprises determining the loss of the total wavelength power as follows:

$L_{k,k+i}=\left(1/M\right)*\left(\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k_j}-\underset{j=1}{\overset{M}{\sum <br><br>}}<br><br>P_{k+i_j}\right),$

wherein P_kj is a power of a j^th wavelength at the local detection point (k), P_k+ij is a power of the j^th wavelength at the adjacent detection point (k+i), i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path, and M is a number of wavelengths of said optical fiber.

40. The method as described in claim 38, wherein the step (m) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+i|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+i|_T1|−

W), wherein (W) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+i|_T2); and

(u) if the |L_k,k+i|_T2 in step (t) is less than the respective reference loss value (|L_k,k+i|_T1−

W) in step (s), determining that a faulty component is located between the local detection point and the adjacent detection point.

41. The method as described in claim 40, wherein the pre-determined value (W) is about 1 dB.

42. The method as described in claim 40, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

43. The method as described in claim 40, wherein the step (r) comprises averaging each of the respective (L_k,k+i|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+i|_T2) values over a time interval Δ

T2 preceding T2, and i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path.

44. The method as described in claim 39, wherein the step (m) comprises:

(r) computing the loss of the total wavelength power at a pre-determined time (T1), (L_k,k+i|_T1);

(s) setting the respective reference loss value to be equal to (|L_k,k+i|_T1|−

W) wherein (W) equals to a pre-determined value;

(t) computing the total wavelength power loss at another pre-determined time (T2>

T1), (L_k,k+i|_T2); and

(u) if the |L_k,k+i|_T2| in step (t) is less than the respective reference loss value (|L_k,k+i|_T1|−

W) in step (s), determining that a faulty component is located between the local detection point and the adjacent detection point.

45. The method as described in claim 44, wherein the pre-determined value (W) is about 1 dB.

46. The method as described in claim 44, wherein T2 is a current instance of time, and T2−

T1=Δ

, wherein Δ

is one of the following;

(a) about 1 month;

(b) about 1 week;

(c) about 1 day;

(d) about 1 hour;

(e) about 1 minute;

or

(f) about 1 second.

47. The method as described in claim 44, wherein the step (r) comprises averaging each of the respective (L_k,k+i|_T1) values over a time interval Δ

T1 preceding T1, and the step (t) comprises averaging each of the respective (L_k,k+i|_T2) values over a time interval Δ

T2 preceding T2, and i=1, 2, . . . , N−

1 and N is the total number of detection points along the optical path.

48. An apparatus for determining a faulty component location along an optical path through an optical fiber in an optical network, the optical fiber carrying a plurality of individual wavelengths, the apparatus comprising:

(1) at each of a plurality of local detection points along the optical path, a detector, measuring a total power of the optical fiber;

(2) at each of said local detection points, a detector, measuring a total wavelength power of said individual wavelengths;

(3) a comparator, comparing the total power of the optical fiber in step (1) and the total wavelength power in step (2) for each of said local detection points, and generating a message alert signal indicating that a faulty detection point may exist along the optical path, if a discrepancy between the total power of the optical fiber in step (1) and the total wavelength power in step (2) beyond an accuracy of measurements is detected;

(4) a detector, measuring a loss of a total wavelength power between a local detection point and a detection point adjacent to said local detection point; and

(5) a comparator, for each pair of the local and adjacent detection points comparing the loss of the total wavelength power with a respective reference loss value for the pair, and if the total wavelength power loss in step (4) is less than the respective reference loss value, generating a message alert signal indicating one or more of the following;

a fault occurs at the local detection point,

a fault occurs at the adjacent detection point, and

a faulty component is located between the local detection point and the adjacent detection point.

49. The apparatus as described in claim 48, further comprising:

(6) a detector, measuring a loss of a total wavelength power between a local detection point and a detection point which is non-adjacent to said local detection point; and

(7) a comparator, for each pair of the local and non-adjacent detection points comparing the loss of the total wavelength power with a respective reference loss value for the pair, and if the total wavelength power loss in step (6) is less than the respective reference loss value, generating a message alert signal for one or more of the following;

a faulty component is located between the local detection point and the adjacent detection point, and

a faulty component is located between the local detection point and the non-adjacent detection point.

50. A apparatus for determining a faulty component location along an optical path through an optical fiber in an optical network, the optical fiber carrying a plurality of individual wavelengths, the apparatus comprising:

(i) a detector, measuring a loss of a total wavelength power between a local detection point and a detection point adjacent to said local detection point;

(ii) a comparator, for each pair of the local and adjacent detection points comparing the loss of the total wavelength power with a respective reference loss value for the pair, and if the total wavelengths power loss in step (i) is less than the respective reference loss value, generating a message alert signal for one or more of the following;

a fault occurs at the local detection point,

a fault occurs at the adjacent detection point, and

a faulty component is located between the local detection point and the adjacent detection point;

(iii) a detector, measuring a loss of a total wavelength power between the local detection point and a detection point, which is non-adjacent to, said local detection point;

(iv) a comparator, for each pair of the local and non-adjacent detection points comparing the loss of the total wavelength power with a respective reference loss value for the pair, and if the total wavelengths power loss in step (iii) is less than the respective reference loss value, generating a message alert signal for one or more of the following;

a fault occurs at the non-adjacent detection point,

a faulty component is located between the local detection point and the adjacent detection point, and

a faulty component is located between the local detection point and the non-adjacent detection point.