Cross talk between neighboring optical fibers is shown to alter the absorption spectrum of the fibers. There is an enhancement of absorption at shorter wavelengths and a consequent shift of the absorption peak towards the short-wavelength end of the spectrum. Curves are presented to illustrate the effect. Results are given in a dimensionless form, applicable to fibers with arbitrary physical parameters.
Peter McIntyre, "Cross talk in absorbing optical fibers," J. Opt. Soc. Am. 65, 810-813 (1975)