Specialty Optical Fibers Handbook

channel at a single wavelength. Network architecture changed dramatically when

single-mode EDFAs for direct optical amplification of 1:5-mm signals were

simultaneously developed by AT&T Bell Laboratories [52] and the University

of Southampton [53] in 1987. The efforts directed at development of techniques

for producing high-quality RE fibers suddenly bore fruit as Er amplifiers

emerged to fill a critical need. Optical amplifiers are a tremendous advantage

because they directly amplify the optical signal, support multiple wavelengths,

and are independent of bit rate. By 1989, the first EDFA pumped by an efficient

semiconductor laser had been demonstrated [54], and in 1994, the first undersea

optical amplifiers were deployed by AT&T Submarine Systems ...