In a method for performing OTDR measurement in an optical transmission system including a first terminal station and a second terminal station, OTDR signal light is transmitted from an OTDR provided in the first terminal station to the second terminal station, in which the OTDR signal light is Raman amplified by using main signal light of the optical transmission system as pump light. The liposomal formulations comprise a porphyrin photosensitizer, particularly the hydro-mono benzoporphyrins having light absorption maxima in the range of 670\u2013780 nanometers, a disaccharide or polysaccharide and one or more phospholipids. The slot motors each have two side legs opposing each other and defining a space therebetween for receiving the movable contact arm, each side leg having a magnetic core and an insulative layer and being biased toward the interior of the side walls of the cassette, wherein each side leg is restrained from being magnetically attracted toward the movable contact arm during a short circuit condition. The driving side roller portions are rotationally driven, thereby transporting the recording medium.