Fast dynamic gain control in cascaded Raman fiber amplifiers

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United States Patent

Zhou et al.

(io) Patent No.: (45) Date of Patent:

US 7,280,270 B2 Oct. 9, 2007

FAST DYNAMIC GAIN CONTROL IN
CASCADED RAMAN FIBER AMPLIFIERS

Inventors: Xiang Zhou, Holmdel, NJ (US);

Martin Birk, Belford, NJ (US)

Assignee: AT&T Corporation, Bedminster, NJ
(US)

Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

Appl. No.: 11/424,309

Filed: Jun. 15, 2006

Prior Publication Data

US 2007/0109625 Al May 17, 2007

Related U.S. Application Data

Continuation-in-part of application No. 11/274,666, filed on Nov. 15, 2005, now Pat. No. 7,142,356.

Int. CI.

H01S 4/00 (2006.01)
H04B 10/12 (2006.01)

U.S. CI 359/334

Field of Classification Search 359/344,

359/334

See application file for complete search history.
References Cited
U.S. PATENT DOCUMENTS

6,958,856 B2 10/2005 Inoue et al.

(Continued)
FOREIGN PATENT DOCUMENTS
EP 1248 334 10/2002

(Continued)

OTHER PUBLICATIONS

Yihong, Chen et al., "Bi-directionally pumped broadband Raman amplifier," ECOC, Sep. 2001, pp. 230-231, Freehold, NJ.

(Continued)

Primary Examiner—Jack Keith
Assistant Examiner—Eric Bolda

(74) Attorney, Agent, or Firm—Banner & Witcoff, Ltd.

359/337.11

The present invention provides methods and apparatuses for controlling a gain of a bidirectionally-pumped Raman fiber amplifier having both forward optical pumps and backward optical pumps. The overall gain is controlled by adjusting the forward optical pumps, while the power levels of the backward optical pumps are essentially fixed. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one forward optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump.

10 Claims, 38 Drawing Sheets

Chen, C.J. et al., "Control of transient effects in distributed and lumped Raman amplifier," Electronic Letters, Oct. 2001, pp. 13041305, vol. 37, No. 21, USA.

Wang, L.L., et al., "Gain transients in co-pumped and counterpumped Raman amplifiers," IEEE Photonics Technology Letters, May 2003, pp. 664-666, vol. 15, No. 5, USA. Zhou, Xiang et al., "Theoretical investigation of fiber Raman amplifier with dynamic gain control", OFC, 2001, pp. WDD17-1WDD17-3, Singapore.

Bolognini, G. et al., "Transient effects in gain-clamped discrete Raman amplifier cascades", IEEE Photonics Technology Letters, Jan. 2004, pp. 66-68, vol. 16, No. 1, USA.

Zhou, Xiang et al., "Submicrosecond Transient Control for a Forward-Pumped Raman Fiber Amplifier", IEEE Photonics Technology Letters, 2005, pp. 2059-2061, vol. 17, No. 10, USA. Zhou, Xiang et al., "A new technique for dynamic gain profile control in a multi-wavelength backward-pumped discrete Raman amplifier", 2001, pp. 1-3, USA.

Kim, Pilhan et al. "Semianalytic Dynamic Gain-Clamping Method for the Fiber Raman Amplifier", IEEE Photonics Technology Letters, Apr. 2005, pp. 768-770, vol. 17, No. 4, USA.

* cited by examiner