STABILIZATION OF TRANSMISSION FUNCTION - THEORY FOR AN ULTRATHIN ENDOSCOPE OF ONE MULTIMODE FIBER

Propagation of a monochromatic light through a multimode fiber is cons idered in connection with the problem of image transmission. We discus s the variations of throughput scrambling, i.e., of the pixel-to-pixel Greens' function for transmission under the bends of the fiber axis. Two main statements are elaborated theoretically, which in principle a llow the stabilization of the throughput scrambling. First, if the def ormations are smooth enough, the modes are adiabatically modified with out intermixing. Second, the variation delta phi(m,n) of the phase of a mode M-m,M-n can be expressed as a power series in a small parameter (rho/R)(2) where rho is the core radius and R-1 is the curvature of b ending. A scheme for the compensation of those phase shifts is suggest ed based on prebending of the fiber with subsequent controllable adjus tment of that prebending. (C) 1997 Optical Society of America.