United States Patent m
Desurvire et al.
[ii] Patent Number: 4,815,804 [45] Date of Patent: * Mar. 28, 1989
[54] IN-LINE FIBER OPTIC MEMORY AND METHOD OF USING SAME
[75] Inventors: Emmanuel Desurvire, Menlo Park;
Michel J. F. Digonnet, Palo Alto; H.
J. Shaw, Stanford, all of Calif.
[73] Assignee: The Board of Trustees of the Leland Stanford Junior University, Stanford, Calif.
[ * ] Notice: The portion of the term of this patent subsequent to Nov. 24, 2004 has been disclaimed.
[21] Appl. No.: 123,123
[22] Filed: Nov. 20, 1987
Related U.S. Application Data
[62] Division of Ser. No. 699,853, Feb. 8, 1985, Pat. No. 4,708,421.
[51] Int. CI/ G02B 6/26; G11C 21/00;
H04B 9/00
[52] U.S. CI 350/96.15; 350/96.16;
350/320; 370/3; 365/64; 365/73; 365/76
[58] Field of Search 350/96.10, 96.15, 96.18,
350/96.16, 96.21, 96.20, 96.29, 320, 96.30; 455/600, 612; 370/1, 3; 365/64, 73, 76; 372/3,
6, 30, 31
[56] References Cited
U.S. PATENT DOCUMENTS
4,136,929 1/1979 Suzaki 350/96.15
4,401,364 8/1983 Mochizuki 350/96.16
4,469,397 9/1984 Shawetal 350/96.15
4,473,270 9/1984 Shaw 350/96.15
4,479,701 10/1984 Newton et al 350/96.16
4,493,528 1/1985 Shawetal 350/96.15
4,511,207 4/1985 Newton et al 350/96.15
4,530,097 7/1985 Stokes et al 350/96.15
4,536,058 8/1985 Shaw et al 350/320
4,556,279 12/1985 Shaw et al 350/96.15
4,560,246 12/1985 Cotter 350/96.16
4,616,898 10/1986 Hicks, Jr 350/96.15
4,635,263 1/1987 Mollenauer 372/3
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4,708,421 11/1987 Desurvire et al 350/96.15
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WO86/06885 11/1986 PCT Int'l Appl. 372/6
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(List continued on next page.)
Primary Examiner—William L. Sikes
Assistant Examiner—Brian M. Healy
Attorney, Agent, or Firm—Knobbe, Martens, Olson &
Bear
[57] ABSTRACT
A fiber optic recirculating memory comprises a splicefree length of optical fiber which forms a loop that is optically closed by means of a fiber optic coupler. The coupler couples an optical signal input pulse to the loop for circulation therein, and outputs a portion of the signal pulse on each circulation to provide a series of output pulses. A pump source is included to pump the fiber loop with a pump signal having sufficient intensity to cause stimulated Raman scattering in the fiber loop, and thereby cause amplification of the circulating signal pulse. The fiber characteristics, coupler characteristics, and pump power are selected to yield a Raman gain which compensates for the total round-trip losses in the fiber loop, so as to provide an output pulse train of constant amplitude pulses. The invention may be implemented utilizing either a standard coupler or a multiplexing coupler. The multiplexing coupler advantageously permits independent selection of the coupling ratios for the pump signal and signal pulse, thereby allowing these coupling ratios to be selected for minimum loop loss and maximum pumping efficiency.
21 Claims, 6 Drawing Sheets
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