Figure 7.

Distributions of S/N along the 1.35 m long optical fiber, which were measured and calculated at (a) u_c = −0.042, (b) u_c = 0.45 and (c) u_c = 0.93, where the DFB LD was driven with current source B whose power spectral density is shown in Figure 5b. The scale of the horizontal axis is normalized in such a way that the output end of the fiber under test was unity. The rapid changes of S/N observed around u = 0.31, 0.53 and 0.78 were caused by fusion splicing and mating of the pieces of the optical fiber.