(19)

(11)

EP 0 571 603 A1

(12)

(43) Date of publication: 01.12.1993 Bulletin 1993/48 (21) Application number: 93900523.0 (22) Date of filing: 16.11.1992

(51) International Patent Classification (IPC):  G02B 7/ 00( . ) H01S 3/ 02( . ) G02B 7/ 182( . ) H01S 3/ 086( . ) (86) International application number: PCT/US1992/009888 (87) International publication number: WO 1993/010581 (27.05.1993 Gazette 1993/13)

(84) Designated Contracting States: DE FR GB IT (30) Priority: 15.11.1991 US 19910794729 (71) Applicant: AMOCO CORPORATION Chicago, IL 60680-0703 (US)	(72) Inventors: FISHER, James, Harmon Batavia, IL 60510 (US) RESSL, Michael, Gerard Western Spring, IL 60558 (US) (74) Representative: Low, Peter John  Wilson, Gunn, M'Caw & Co., 41-51 Royal Exchange, Cross Street Manchester, M2 7BD Manchester, M2 7BD (GB)