Patent ID: 7319820

Claim:
A method of manufacturing an optical communication system including (i) an optical fiber and (ii) first and second modules respectively provided at both ends of the optical fiber, the first and second modules simultaneously sending and receiving optical signals via the optical fiber, wherein: a position of the first module with respect to the optical fiber is determined in accordance with a receiving efficiency at the first module with respect to light emitted from the optical fiber; and S 1 _ is set in accordance with a value of FR_ in the position so as to satisfy ( a ) ⁢ ⁢ If ⁢ ⁢ IO ≥ 0.3 ⁢ ( 1 - IO ) 0.7 > S ⁢ ⁢ max * ( NR R ⁢ ⁢ min + FR_ * PT ⁢ ⁢ max 2 ) + X * Namp ⁢ R ⁢ ⁢ min S1_ * PT ⁢ ⁢ min ⁢ ( b ) ⁢ ⁢ If ⁢ ⁢ IO < 0.3 ⁢ 1 > S ⁢ ⁢ max * ( NR R ⁢ ⁢ min + FR_ * PT ⁢ ⁢ max 2 ) + X * Namp ⁢ R ⁢ ⁢ min S ⁢ ⁢ 1 ⁢ _ * PT ⁢ ⁢ min where FR_ is a far-end reflectivity, which is a reflectivity of light that is emitted from the second module and is reflected (i) by the first module and (ii) by the first-module-side end of the optical fiber; S 1 _ is the power of light coupled into the optical fiber from the first module; Smax is a maximum value acceptable in the optical communication system of the power of light coupled into the optical fiber; PTmin is a minimum value acceptable in the optical communication system of a transmittance of the optical fiber with respect to the optical signals; PTmax is a maximum value acceptable in the optical communication system of the transmittance of the optical fiber with respect to the optical signals; NR is a ratio, with respect to Smax, of a stray light component received by the second module, the stray light component being generated on the second-module-side end of the optical fiber and in the second module when light coupled into the optical fiber with power of Smax is emitted from the second module; Rmin is a minimum receiving efficiency at the second module with respect to light emitted from the optical fiber; Namp is a light amount corresponding to a noise in an amplifier for converting, into an electric signal, an optical signal received by the second module; IO is an eye opening ratio required for the electric signal obtained by conversion through the amplifier; and X is a ratio, with respect to Namp, of an optical signal received by the second module when a bit error rate is in an upper limit value acceptable in the optical communication system, and when there is no reflected light returning to the second module after being emitted from the second module.