Measurement of mode conversion coefficients and mode dependent losses in a multimode fiber.

A new method for the simultaneous measurement of the loss and mode conversion coefficient in multimode fibers is proposed, which utilizes the differences of the mean transit time among modes. The principle is applied to a step-index fiber, and the mode conversion coefficient and mode dependent loss are obtained. A procedure to minimize the experimental errors is also discussed. In the experiment the mode conversion coefficient decreases gradually when the mode angle increases and increases rather quickly when the angle approaches the critical angle of the fiber.