Apparatus comprising Raman-active optical fiber
 Raman-active optical fiber having very large Raman cross section is disclosed. The fiber comprises glass that has two major components, a glass-forming first component (GeO.sub.2, SiO.sub.2, AsO.sub.1.5, or combinations thereof) and a heavy metal oxide second component (PbO, BiO.sub.1.5, SbO.sub.1.5, TlO.sub.0.5, or combinations thereof), with the first and second major components making up at least 70 mol %, preferably at least 90 mol %, of the glass. The maximum relative Raman cross section .sigma..sub.r of the inventive glass is at least 15, preferably greater than 20, where .sigma..sub.r =.sigma..sub.RA /.theta..sub.SiO.sbsb.2, and where .sigma..sub.RA and .sigma..sub.SiO.sbsb.2 are the maximum 0.degree. K. Raman cross sections of the inventive glass and of pure vitreous SiO.sub.2, respectively. Fiber according to the invention can advantageously be used in apparatus such as optical fiber communications systems, information processing systems that contain an optical fiber memory loop, and optical fiber sensors. 
American Telephone and Telegraph Company, AT&T Bell Laboratories
H H
H04B H01S
inventional inventional
Anne E. Malcolm E. Kenneth B. Kurt
Miller Lines Lyons Nassau