The characteristics of the receiver used for an optical time-division multiplex transmission system are studied from the signal-to-noise ratio point of view. The receiver, which is characterized by having an optical time-division demultiplexing circuit, has so far been the subject of experimental and analytical discussion only regarding the characteristics of the optical demultiplexing circuit. Taking into account the signal pulse width of the received signal and the frequency bandwidth of the baseband circuit in addition to the optical demultiplexing circuit, we derive the expression of the signal-to-noise ratio, resulting in a systematic analysis of the receiver, which has never before been attempted. For the receiver with an optical time-division demultiplexing circuit, the optimum and allowable baseband bandwidth are quantitatively presented in terms of the signal pulse width and the optical noise power. This provides basic guidelines of receiver design. For instance, when a 20 Gbit/s signal with a 20-ps pulse width is optically demultiplexed into 10 Gbit/s, with a rectangular optical gate, the optimum baseband width is 6.3 GHz. Even for different pulse widths, this bandwidth exhibits signal-tonoise ratio degradation of 1 dB or less in comparison to the receiver with an optimized bandwidth. Furthermore, the requirements for the modulation depth and the width of the optical gate, as well as the phase difference between the optical gate and the signal pulse are discussed.