Attenuation device for wavelength multiplexed optical fiber communications

• US 5,745,271 A
• Filed: 07/31/1996
• Issued: 04/28/1998
• Est. Priority Date: 07/31/1996
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Miller, David Andrew Barclay, Walker, James Albert, Nuss, Martin C., Ford, Joseph Earl
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US08/690,696
• Time in Patent Office: 636 Days
• Field of Search: 359/127, 359/128, 359/130-131, 359/161, 359/126, 385/10, 385/24, 385/37, 385/140
• US Class Current: 398/87
• CPC Class Codes: G02B 2006/12123 Diode
• CPC Class Codes: G02B 2006/12142 Modulator
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/4215 the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers G02B6/4246 takes precedence
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant

Abstract

An optical signal attenuation device and associated method for selectively attenuating the signal strengths of different wavelength signals contained within a multiplexed optical transmission. The attenuation device includes a diffracting element that diffracts the multiplexed optical system and directs the different wavelength signals onto separate optical paths. A modulator array is provided that contains a plurality of optical modulators spaced at a pitch so that each modulator receives one of the different wavelength signals. Each optical modulator causes a signal to be produced that correspond to the signal it receives, except that the signal strength of the emitted signal is altered to fall within a desired range. Each signal emitted by the optical modulators is again directed toward a diffraction element. The diffraction element combines the separate wavelength signals, thereby producing a multiplexed signal where each wavelength has a signal strength that falls within a common range.

Claims

1. An optical signal attenuation device for selectively attenuating different wavelength signals contained within a multiplexed transmission, comprising:

a first diffraction element for diffracting the light associated with the multiplexed transmission, wherein each wavelength signal contained within the multiplexed transmission is directed along a separate optical path; and

a modulator disposed along each separate optical path, wherein each modulator receives a wavelength signal from said diffraction element and causes a corresponding signal to be produced at a selective optical signal strength.

2. The device according to claim 1, wherein each signal produced by each said modulator is directed back through said first diffraction element, whereby said first diffraction element multiplexes each signal.

3. The device according to claim 1, further including a second diffraction element, wherein each signal produced by each said modulator is directed through said second diffraction element and said second diffraction element multiplexes each signal.

4. The device according to claim 1, further including a first collimator for substantially collimating the light associated with the multiplexed transmission, prior to the light being diffracted by said first diffraction element.

5. The device according to claim 1, further including a focusing lens arrangement disposed between said first diffraction element and each said modulator for focusing each wavelength signal onto a corresponding modulator.

6. The device according to claim 4, wherein the multiplexed transmission travels along an optical input fiber and said first collimator collimates the light, associated with the multiplexed transmission, emitted by the optical input fiber.

7. The device according to claim 6, further including a second collimator for focusing each signal emitted by each said modulator at an optical output fiber.

8. The device according to claim 1, wherein said first diffraction element is a diffraction grating.

9. An optical signal attenuation device for selectively attenuating different wavelength signals contained within a multiplexed transmission, comprising:

a first diffraction element for diffracting the light associated with the multiplexed transmission, wherein each wavelength signal contained within the multiplexed transmission is directed along a separate optical path;

a modulator disposed along each separate optical path, wherein each modulator receives a wavelength signal from said diffraction element and causes a corresponding signal to be produced at a selective optical signal strength; and

a plurality of optical power detectors for detecting the optical power associated with each wavelength signal received by each said modulator.

10. The device according to claim 9, further including an optical element disposed between each said modulator and said first diffraction element for directing a portion of each wavelength signal emitted by said first diffraction element toward one of said plurality of optical power detectors.

11. An optical signal attenuation device for selectively attenuating different wavelength signals contained within a multiplexed transmission, comprising:

a first diffraction element for diffracting the light associated with the multiplexed transmission, wherein each wavelength signal contained within the multiplexed transmission is directed along a separate optical path;

a modulator disposed along each separate optical path, wherein each modulator receives a wavelength signal from said diffraction element and causes a corresponding signal to be produced at a selective optical signal strength; and

a plurality of optical power detectors for detecting the optical power associated with each signal produced by each said modulator.

12. The device according to claim 11, further including a partially reflective surface disposed between each said modulator and said first diffraction element for reflecting a portion of each signal produced by each said modulator toward one of said plurality of optical power detectors.

13. An optical signal attenuation device for selectively attenuating different wavelength signals contained within a multiplexed transmission, comprising:

a first diffraction element for diffracting the light associated with the multiplexed transmission, wherein each wavelength signal contained within the multiplexed transmission is directed along a separate optical path;

a modulator disposed along each separate optical path, wherein each modulator receives a wavelength signal from said diffraction element and causes a corresponding signal to be produced at a selective optical signal strength; and

a first plurality of optical power detectors for detecting the optical power associated with each wavelength signal received by each said modulator and a second plurality of optical power detectors for detecting the optical power associated with each signal produced by each said modulator.

14. The device according to claim 13, wherein each modulator includes a control circuit that controls the selective optical signal strength of the signal produced by each said modulator, wherein said control circuit maintains the selective optical signal strength at a value that is a function of a ratio between the optical power of each wavelength signal received by each said modulator and the optical power each signal produced by each said modulator.

15. The device according to claim 13, wherein said first plurality of optical power detectors, said second plurality of optical power detectors and each said modulator are disposed on a common semiconductor device.

16. In an optical network containing a plurality of optical fibers and at least one optical switch for selectively optically connecting at least some of said optical fibers together into one of a plurality of configurations, wherein each of the configurations disproportionately effects the signal strengths of the different wavelength signals contained within a multiplexed optical signal and causes the different signal strengths to vary in relation to one another outside an acceptable range, an attenuation device for correcting the optical signal, comprising:

a first plurality of detectors for detecting the signal strength corresponding to each wavelength signal contained within the multiplexed optical signal; and

an attenuator, coupled to said first plurality of detectors, for selectively attenuating the signal strength for each wavelength signal in the multiplexed optical signal to produce a corrected wavelength signal, wherein the signal strength for each corrected wavelength signal falls within said acceptable range.

17. The device according to claim 16, wherein said attenuator includes a first diffraction grating for diffracting the multiplexed optical signal, wherein each wavelength signal contained within the multiplexed optical signal is directed along a separate optical path;

and

a modulator disposed along each separate optical path, wherein each modulator receives a wavelength signal from said first diffraction grating and produces said corrected wavelength signal.

18. The device according to claim 17, wherein each signal produced by each said modulator is directed back through said first diffraction element, whereby said first diffraction element multiplexes each signal.

19. The device according to claim 17, further including a second diffraction element, wherein each signal produced by each said modulator is directed through said second diffraction element and said second diffraction element multiplexes each signal.

20. The device according to claim 16, further including a second plurality of detectors for detecting the signal strength corresponding to each corrected wavelength signal.

21. A method of equalizing the signal strengths of the different wavelength signals contained within a multiplexed optical signal, comprising the steps of:

separating each of said wavelength signals from said multiplexed optical signal;

correcting the signal strength associated with each of said wavelength signals so that the signal strength of each of said wavelength signals falls within a compatible range; and

multiplexing each of said wavelength signals to produce a corrected multiplexed optical signal wherein all the wavelengths contained within the corrected multiplexed optical signal have a signal strength within said compatible range.

22. The method according to claim 21, wherein said step of separating each of said wavelength signals includes directing the light corresponding to said multiplexed optical signal onto a first diffraction grating, wherein the first diffraction grating directs each of said wavelength signals along a separate optical path.

23. The method according to claim 21, wherein said step of correcting the signal strength includes providing a modulator on each of said separate optical paths, wherein each modulator receives one of said wavelength signals and produces a corresponding corrected signal that has a signal strength that falls within said compatible range.

24. The method according to claim 21, wherein said step of multiplexing includes directing each said corresponding corrected signal toward said first diffraction grating, wherein said first diffraction grating combines each said corresponding corrected signal and produces said corrected multiplexed optical signal.

25. The method according to claim 21, wherein said step of multiplexing includes directing each said corresponding corrected signal toward said second diffraction grating, wherein said second diffraction grating combines each said corresponding corrected signal and produces said corrected multiplexed optical signal.

26. The method according to claim 22, further including the step of collimating the light of said multiplexed signal prior to the light being diffracted by said first diffraction grating.

27. The method according to claim 21, further including the step of focusing each of said wavelength signals on each of said separate optical paths onto said modulator.

28. The method according to claim 21, further including the step of detecting the signal strength of each of said wavelength signals in said multiplexed optical signal.

29. The method according to claim 28, further including the step of detecting the signal strength of said wavelength signals after said wavelength signals have been corrected.