Loss-compensation characteristics and noise performance of distributed erbium-doped optical fibers

To realize loss compensated Erbium‐doped (Er‐doped) optical fibers with the intensity deviations of the propagating light signal suppressed below a few decibels, first, numerical simulations of the appropriate Er concentration, the anticipated loss compensation length, and the noise figure are carried out. Hence, the intensity deviations of the light signal of 1.535‐μm wavelength can be kept below 1 to 3 dB at 60 mW pumping power of 1.48‐μm wavelength allowing 30 to 40 km long loss‐compensated fibers to be produced. Based on these results, an Er‐doped 36.8‐km long fiber actually is manufactured where the intensity deviations of the propagating light signal over the whole length is about 1 dB at pumping power of 66 mW. It is shown experimentally that it is possible to produce loss‐compensated 73.6‐km long fibers using the bidirectional pumping method. The experimental results of the noise figure are in good agreement with those of the simulation ones.