An estimating device comprising: a detector (14, 15, 16) adapted to detect a first parameter representing a ratio of a power of a signal component other than a noise in received light to a power of a noise component consisting of the noise in the received signal, a second parameter representing a sum of the power of the signal component and the power of the noise component, and a third parameter representing a sum of a power of a component being derived from cross phase modulation and being contained in the noise component and a power of a component being derived from spontaneously emitted light and being contained in the noise component; and an estimator adapted to estimate, based on the first through the third parameters, a fourth parameter representing a ratio of the power of the signal component to a power of a component being derived from self phase modulation and being contained in the noise component, wherein the estimator is adapted to estimate the fourth parameter using Expression 42, P s P SPM = α + 1 R OSNR α − R OSNR where, P s/ P SPM represents the fourth parameter, P s represents the power of the signal component, P SPM represents the power of the component being derived from the self phase modulation and being contained in the noise component, R OSNR is represented by Expression 43 and represents the first parameter, R OSNR = P s P n where, P n is represented by Expression 44 and represents the power of the noise component, P n = P ASE + P SPM + P XPM where, P XPM represents the power of the component being derived from the cross phase modulation and being contained in the noise component, P ASE represents the power of the component being derived from the spontaneously emitted light and being contained in the noise component, and α is represented by Expression 45, α = P t − P A P A where, P t is represented by Expression 46 and represents the second parameter, P t = P s + P n where, P A is represented by Expression 47 and represents the third parameter, P A = P ASE + P XPM a detector (14, 15, 16) adapted to detect a first parameter representing a ratio of a power of a signal component other than a noise in received light to a power of a noise component consisting of the noise in the received signal, a second parameter representing a sum of the power of the signal component and the power of the noise component, and a third parameter representing a sum of a power of a component being derived from cross phase modulation and being contained in the noise component and a power of a component being derived from spontaneously emitted light and being contained in the noise component; and an estimator adapted to estimate, based on the first through the third parameters, a fourth parameter representing a ratio of the power of the signal component to a power of a component being derived from self phase modulation and being contained in the noise component, wherein the estimator is adapted to estimate the fourth parameter using Expression 42, P s P SPM = α + 1 R OSNR α − R OSNR where, P s/ P SPM represents the fourth parameter, P s represents the power of the signal component, P SPM represents the power of the component being derived from the self phase modulation and being contained in the noise component, R OSNR is represented by Expression 43 and represents the first parameter, R OSNR = P s P n where, P n is represented by Expression 44 and represents the power of the noise component, P n = P ASE + P SPM + P XPM where, P XPM represents the power of the component being derived from the cross phase modulation and being contained in the noise component, P ASE represents the power of the component being derived from the spontaneously emitted light and being contained in the noise component, and α is represented by Expression 45, α = P t − P A P A where, P t is represented by Expression 46 and represents the second parameter, P t = P s + P n where, P A is represented by Expression 47 and represents the third parameter, P A = P ASE + P XPM P s/ P SPM represents the fourth parameter, P s represents the power of the signal component, P SPM represents the power of the component being derived from the self phase modulation and being contained in the noise component, R OSNR is represented by Expression 43 and represents the first parameter, R OSNR = P s P n where, P n is represented by Expression 44 and represents the power of the noise component, P n = P ASE + P SPM + P XPM where, P XPM represents the power of the component being derived from the cross phase modulation and being contained in the noise component, P ASE represents the power of the component being derived from the spontaneously emitted light and being contained in the noise component, and P XPM represents the power of the component being derived from the cross phase modulation and being contained in the noise component, P ASE represents the power of the component being derived from the spontaneously emitted light and being contained in the noise component, and α is represented by Expression 45, α = P t − P A P A where, P t is represented by Expression 46 and represents the second parameter, P t = P s + P n where, P A is represented by Expression 47 and represents the third parameter, P A = P ASE + P XPM where, P t is represented by Expression 46 and represents the second parameter, P t = P s + P n where, P A is represented by Expression 47 and represents the third parameter, P A = P ASE + P XPM