| 摘要 |
PURPOSE:To obtain two local oscillation light beams which have sufficient power by providing a 1/2-wavelength plate and utilizing light beams from both ends of a both-end light emission type semiconductor laser. CONSTITUTION:One local oscillation light (S polarized wave) emitted by one end surface of the both-end light emission type semiconductor laser 7 is changed in polarization state by the 1/2-wavelength plate 14 and has its plane of polarization rotated by 90 deg. to become a P polarized wave. The local oscillation light in the P polarized wave state which is changed in polarization state as mentioned above and local oscillation light emitted by the other end surface of the both-end light emission type semiconductor laser 7 are inputted to a mixing circuit 8, which mixes two kinds of polarized components of signal light sent through an optical fiber 5 by P polarized waves and S polarized waves. Then a detecting circuit 9 detects each polarized wave and a signal composing circuit 10 demodulates, adds, and discriminates them with the input signal. Consequently, the two local oscillation light beams which have sufficient power are obtained. |
