Systems and methods for detecting fault conditions and detecting and preventing potentially dangerous conditions in an optical system

• US 6,547,453 B1
• Filed: 08/30/2000
• Issued: 04/15/2003
• Est. Priority Date: 01/12/2000
• Status: Expired due to Fees

• Current Assignee: Ciena Corporation
• Original Assignee: Ciena Corporation
• Inventors: Friedrich, Lars, Stummer, Alan D.
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US09/651,501
• Time in Patent Office: 958 Days
• Field of Search: 385/24, 385/88, 385/89, 385/90, 385/91, 385/147, 359/900
• US Class Current: 385/88
• CPC Class Codes: H04B 10/071 using a reflected signal, e.g. using optical time domain reflectometers [OTDR]

Abstract

A system detects potentially dangerous conditions, prevents damage to optical components, and prevents humans from being physically harmed by stray pumping light. Optical systems employing distributed amplification such as Raman amplification utilize pumps having high output powers. These high output powers create dangerously high power densities in the optical fiber. If a connection is imperfect a hot spot may develop and the connection damaged by the pumping light. Fiber damage, disconnections and component degradations or failures may also permit the pumping light to escape the intended path and cause physical harm to humans as well as equipment. Pumping light backreflections caused by such imperfect connections, degraded/failed components, and fiber damage are detected. A controller compares the backreflection amount against a threshold to determine whether a precautionary measure should be taken such as shutting down the pump, decreasing pump power to a safe level or setting a maintenance flag. Multiple thresholds may be utilized to distinguish between different conditions such as degraded and failed conditions and to exercise appropriate levels of precautionary measure(s). The detection of distributed pumping light backreflections may also be used to shut or power down other types of pumps such as an EDFA.

Claims

1. An apparatus for controlling an amplified optical system, comprising

an optical pump source operatively connected to a fiber optic system having an optical fiber,

said optical pump source operable at a pumping wavelength selected to provide gain to a signal travelling in a segment of the optical fiber, wherein the pumping wavelength is different than a signal wavelength;

wherein the optical fiber transmits a pumping light signal from said optical pump source and a reflected pumping light signal when the optical fiber is damaged or when a component in the optical system is degraded or failed;

a back reflection detector operatively connected to the optical fiber, said back reflection detector configured to detect an amount of the reflected pumping light signal; and

a controller operatively connected to said optical pump source and to said back reflection detector;

said controller taking at least one precautionary measure when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds a threshold value.

2. The apparatus for controlling an amplified optical system according to claim 1,

wherein the at least one precautionary measure includes reducing output power of said optical pump source,

said controller reducing the optical pump source output power of said optical pump source when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the threshold value.

3. The apparatus for controlling an amplified optical system according to claim 1,

wherein the at least one precautionary measure includes shutting down said optical pump source,

said controller shutting down said optical pump source when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the threshold value.

4. The apparatus for controlling an amplified optical system according to claim 1, wherein

the threshold value includes at least a first threshold value and a second threshold value,

wherein the at least one precautionary measure includes shutting down or reducing output power of said optical pump source,

said controller reducing the optical pump source output power of said optical pump source when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the first threshold value;

and

said controller shutting down said optical pump source when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the second threshold value.

5. The apparatus for controlling an amplified optical system according to claim 1,

wherein the at least one precautionary measure includes setting a maintenance flag,

said controller setting the maintenance flag when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the threshold value.

6. The apparatus for controlling an amplified optical system according to claim 1, further comprising:

at least one second optical pump source operatively connected to the fiber optic system,

wherein the at least one precautionary measure includes reducing output power of said first and second optical pump sources,

said controller reducing optical pump source output power of said first and second optical pump sources when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the threshold value.

7. The apparatus for controlling an amplified optical system according to claim 1, further comprising:

at least one second optical pump source operatively connected to the fiber optic system,

wherein the at least one precautionary measure includes shutting down said first and second optical pump sources,

said controller shutting down said first and second optical pump sources when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the threshold value.

8. The apparatus for controlling an amplified optical system according to claim 1,

wherein the at least one precautionary measure includes controlling output power of said optical pump source,

the apparatus further comprising:

a switchable attenuator operatively connected to said controller and operatively connected between said optical pump source and the fiber optic system;

said controller reducing the optical pump source output power of said optical pump source by controlling said switchable attenuator to attenuate at least a portion of the pumping light signal when the detected amount of the reflected pumping light signal detected by said back reflection detector exceeds the threshold value.

9. The apparatus for controlling an amplified optical system according to claim 1,

said second optical pump source pumping a segment of the optical fiber doped with an optically active material.

10. The apparatus for controlling an amplified optical system according to claim 1,

said optical pump source emitting the pumping light signal with increasing power during power up.

11. The apparatus for controlling an amplified optical system according to claim 1,

said backreflection detector and said controller being operable during power up and operational modes.

12. The apparatus for controlling an amplified optical system according to claim 1,

said controller determining a ratio of power of the pumping light signal emitted by said optical pump source to power of the reflected pumping light signal,

said controller comparing the ratio to the threshold to determine whether to take the at least one precautionary measure.

13. The apparatus for controlling an amplified optical system according to claim 1,

said optical pump source operatively connected to the fiber optic system to provide counterpropagating or copropagating gain to a signal travelling in a segment of the optical fiber,

said optical pump source operable at a pumping wavelength selected to provide Raman or Brillouin gain to a signal travelling in a segment of the optical fiber.

14. The apparatus for controlling an amplified optical system according to claim 1,

said optical pump source including a plurality of pumping lasers.

15. The apparatus for controlling an amplified optical system according to claim 1, further comprising:

a wavelength selective coupler operatively connected to a first and a second section of the optical fiber, said wavelength selective coupler transmitting optical signals in a first wavelength range between the first and second sections of the optical fiber,

said wavelength selective coupler transmitting optical signals in a second wavelength range from the first section of the optical fiber to an output of said wavelength selective coupler, wherein the second wavelength range includes the pumping wavelength of the reflected pumping light signal,

a coupler operatively connected to said optical pump source, said backreflection detector, and the output of said wavelength selective coupler,

said coupler receiving the reflected light signal from said wavelength selective coupler and transmitting a first portion of the reflected light signal to said optical pump source and a second portion of the reflected light signal to said backreflection detector,

said coupler and said wavelength selective coupler transmitting the pumping light signal from said optical pump source to the first section of optical fiber.

16. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value, wherein the at least one precautionary measure includes reducing output power of the optical pump source; and

reducing the optical pump source output power of the optical pump source when the detected amount of the reflected pumping light signal detected by said detection step exceeds a threshold value.

17. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value;

wherein the at least one precautionary measure includes shutting down the optical pump source; and

shutting down the optical pump source when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the threshold value.

18. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value;

wherein the threshold value includes a first threshold value and a second threshold value,

wherein the at least one precautionary measure includes shutting down or reducing output power of the optical pump source,

reducing the optical pump source output power of the optical pump source when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the first threshold value; and

shutting down the optical pump source when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the second threshold value.

19. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value;

wherein the at least one precautionary measure includes setting a maintenance flag; and

setting the maintenance flag when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the threshold value.

20. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value;

wherein the optical system includes a second optical pump source,

wherein the at least one precautionary measure includes reducing output power of the first and second optical pump sources; and

reducing optical pump source output power of the first and second optical pump sources when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the threshold value.

21. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value;

wherein the optical system further includes a second optical pump source,

wherein the at least one precautionary measure includes shutting down the first and second optical pump sources; and

shutting down the first and second optical pump sources when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the threshold value.

22. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value; and

emitting the pumping light signal with increasing power during power up of the optical pump source.

23. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value; and

continuously performing said detecting and taking steps during power up and operational modes of the optical pump source.

24. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value; and

determining a ratio of power of the pumping light signal emitted by the optical pump source to power of the reflected pumping light signal,

said taking step comparing the ratio to the threshold.

25. A method for controlling an amplified optical system including an optical fiber and an optical pump source providing gain to a signal travelling in a segment of the optical fiber, the method comprising:

detecting a reflected pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed;

taking at least one precautionary measure when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value,

wherein the optical pump source provides Raman or Brillouin gain to a signal travelling in a segment of the optical fiber.

26. A method for detecting signal path integrity in a fiber optic system including an optical fiber and an optical pump source, the method comprising:

providing gain to a signal travelling in a segment of the optical fiber with a pumping light signal from the optical pump source;

detecting a reflected pumping light signal, wherein the reflected pumping light signal is a reflection of the pumping light signal from the optical pump source that is reflected when the optical fiber is damaged or when a component in the optical system is degraded or failed; and

determining that the signal path integrity is compromised when a detected amount of the reflected pumping light signal detected by said detecting step exceeds a threshold value.

27. The method for detecting signal path integrity in a fiber optic system according to claim 26,

wherein the threshold value includes a first threshold value and a second threshold value,

said determining step determining that the signal path integrity is in a degraded state when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the first threshold value; and

said determining step determining that the signal path integrity is in a failed state when the detected amount of the reflected pumping light signal detected by said detecting step exceeds the second threshold value.

28. The method for detecting signal path integrity in a fiber optic system according to claim 26, wherein the gain is Raman or Brillouin gain.