Abstract
Outer fibers, inner segments and outer segments of L-cell and M-cell on human retina are single mode fibers. In this paper, we find two neighboring L-cell and M-cell act as an optical fiber coupler which is similar to couplers widely used in the optical communication systems. We first propose that two neighboring cones are divided into two regions, namely strong coupling region and weak coupling region. The strong coupling region includes outer fibers and inner segments. The weak coupling region includes outer segments. We call the couplers consisted of cones as cone couplers. We find cone couplers are very similar to the Wavelength Division Multiplexing (WDM) couplers which are widely used in the optical communication systems. We simulate the power ratios of cone couplers, which are consisted of outer fibers and inner segments with length of 80–110μm, and diameter of 1.6–2μm, and relative refractive index difference of 0.91%, where they are close to the real values of central foveal cones. Contrary to the traditional understanding, our results show that when a red light incidents into the outer fiber of the M-cell, it will be almost fully coupled into the outer segment of adjacent L-cell instead of M-cell. The traditional explanation of color antagonism is that it comes from signal processing in electrical domain, but our results show that it is related to the strong coupling of cone couplers in optical domain. Our results will be very important for people to understand and treat the color-blindness and color-weakness.