Abstract: In the semiconductor memory device relating to the present invention, the memory is divided into a plurality of blocks having a plurality of sectors and stores user data in units of sectors. When writing one sector of user data, the controller converts the logical block address to a physical block address using the address table. The controller selects one unused block and writes one sector of user data to this unused block. When user data are stored in this unused block, all data in this block are deleted before data are written thereto. Next, the controller reads data corresponding to other sectors from a block corresponding to the physical block address discussed above and copies this data in order to an unused block. When the writing ends, the control portion overwrites the address table so that the physical address of this unused block is assigned to the logical block address discussed above.

Abstract: Optical fiber amplifiers with a simple composition than can accurately flatten optical output power in a fixed range are provided. Main optical amplifiers and first gain equalizers connected to these amplifiers are disposed between input port and output port. The main optical amplifiers comprise first EDFs which function as first amplification optical fibers, pumping light sources for providing pumping to drive the first EDFs using amplification characteristics, and second isolators. It is preferable for the second isolators to be isolators that can eliminate optical pumping power. The first gain equalizers are comprised by second absorption EDF. This second EDF operates such that the gain of the optical signal decreases in a non-pumping state or in a slight pumping state. The amplification characteristics used by the first EDF to amplify the optical signal power are opposite to the absorption characteristics used by the second EDF to absorb the optical signal power.