Experimental studies of optical Raman amplifiers for 1.3-mm wavelength band and its application to 20 Gbit/s X 2 WDM transmission

Configurations of a Raman amplifier suitable for a 1.3-mm wavelength band are discussed and their properties are experimentally investigated. Pump light with a wavelength of 1.23 mm that is necessary for the Raman amplification in the 1.3-mm wavelength band is obtained using a 1.06-mm fiber laser and Raman laser technique. Concerning the Raman laser, wavelength conversion from 1.06 mm to 1.23 mm is effectively achieved using a cavity configuration including fiber Bragg gratings and a dispersion-shifted fiber. On the other hand, a conventional dispersion compensation fiber which has an essential property of high nonlinearity is applied in order to obtain large gain at 1.3 mm. Net gain of 35 dB and output power of 15 dBm are achieved. To confirm the applicability of the Raman amplifiers to high-speed optical transmissions, experiments of 20 Gbit/s X 2 WDM repeaterless transmission through a 80-km conventional single-mode fiber are carried out. The 1.3-mm signal should be degraded due to the dispersion caused by the dispersion compensation fiber in the Raman amplifier; However, bit error rate of less than 10 to 12 is obtained at both wavelengths, which is sufficient performance for practical uses.