Abstract: A canceling method and apparatus can achieve a fast communication by improving an S/N value by adaptively canceling a noise with respect to a frequency or band having a large noise by selecting noise canceling band in accordance with a condition of noise being generated. A reception signal contains a specific signal having a specified time position, amplitude and phase. A noise distribution of the specific signal is recognized so as to predict a noise by extracting a frequency band having a larger noise component from a pair of frequencies generated by the insertion of the specific signal. An original transmission signal is reproduced by canceling the predicted noise from the reception signal.

Abstract: A communication system capable of performing efficient Wavelength Division Multiplexing (WDM) transmission by flexibly handling connection services. A Bit Error Rate (BER) measurement unit measures BER of individual optical signals with different wavelengths. A BER transmission unit transmits BER information to the sending end. A wavelength assignment unit assigns each wavelength to at least one of high Quality-of-Service (QoS) communication and low QoS communication. A wavelength-assignment exchanging unit identifies low quality wavelengths with high BERs being used for the high QoS communication, and unless the low quality wavelengths being used for the high QoS communication outnumber the high quality wavelengths with low BERs being used for the low QoS communication, it exchanges the low quality wavelengths and an equal number of the high quality wavelengths. An optical signal transmission unit multiplexes the wavelengths to transmit the optical signals.