Abstract: An optical transmission system is configured to optically transmit data from an optical transmitter to an optical receiver using a plurality of subcarriers. The optical transmitter includes a control unit configured to transmit a measurement signal using a subcarrier included in a band used for optical transmission when a signal is communicated to the optical receiver, the control unit being configured to calculate transmission characteristics obtained between the optical transmitter and the optical receiver based on the measurement signal returned from the optical receiver, and the control unit being configured to allocate, based on the transmission characteristics, a communication link to a subcarrier excellent in the transmission characteristics and least affecting transmission capacity. The optical receiver is configured to return the measurement signal received thereby to the optical transmitter.

Abstract: An optical transmission system is configured to optically transmit data from an optical transmitter to an optical receiver using a plurality of subcarriers. The optical transmitter includes a control unit configured to transmit a measurement signal using a subcarrier included in a band used for optical transmission when a signal is communicated to the optical receiver, the control unit being configured to calculate transmission characteristics obtained between the optical transmitter and the optical receiver based on the measurement signal returned from the optical receiver, and the control unit being configured to allocate, based on the transmission characteristics, a communication link to a subcarrier excellent in the transmission characteristics and least affecting transmission capacity. The optical receiver is configured to return the measurement signal received thereby to the optical transmitter.

Abstract: An optical receiver includes an optical device that receives input light and converts the input light to an electric signal; an equalizer that carries out waveform shaping on the electric signal; an amplifier that amplifies the electric signal; a discrimination part that discriminates data of the electric signal; an input optical power detecting part that detects input optical power of the input light; and a control part that makes an error rate in the electric signal with respect to the input optical power worse when the input optical power detected by the input optical power detecting part is equal to or less than a value corresponding to minimum receiver sensitivity.

Abstract: An optical receiver includes an optical device that receives input light and converts the input light to an electric signal; an equivalent part that carries out waveform shaping on the electric signal; an amplifier that amplifies the electric signal; a discrimination part that discriminates data of the electric signal; an input optical power detecting part that detects input optical power of the input light; and a control part that makes an error rate in the electric signal with respect to the input optical power worse when the input optical power detected by the input optical power detecting part is equal to or less than a value corresponding to minimum receiver sensitivity.

Abstract: An apparatus is provided with a biasing unit supplying a bias signal to a first avalanche photodiode and a second avalanche photodiode, the bias signal having a first level and a second level, the first level causing a multiplying effect and the second level causing a non-multiplying effect for the first and the second avalanche photodiodes; a smoothing unit smoothing the bias signal biasing the first avalanche photodiode into a smoothed bias signal; a current detecting unit detecting photocurrent from the second avalanche photodiode, with a multiplying current value corresponding to the multiplying bias level and a non-multiplying current value corresponding to the non-multiplying bias level; a multiplication factor calculating unit calculating a multiplication factor of the second avalanche photodiode based on the multiplying current value and the non-multiplying current value; and a control unit controlling the first level of the bias signal based on the calculated multiplication factor.

Abstract: An apparatus is provided with a biasing unit supplying a bias signal to a first avalanche photodiode and a second avalanche photodiode, the bias signal having a first level and a second level, the first level causing a multiplying effect and the second level causing a non-multiplying effect for the first and the second avalanche photodiodes; a smoothing unit smoothing the bias signal biasing the first avalanche photodiode into a smoothed bias signal; a current detecting unit detecting photocurrent from the second avalanche photodiode, with a multiplying current value corresponding to the multiplying bias level and a non-multiplying current value corresponding to the non-multiplying bias level; a multiplication factor calculating unit calculating a multiplication factor of the second avalanche photodiode based on the multiplying current value and the non-multiplying current value; and a control unit controlling the first level of the bias signal based on the calculated multiplication factor.