The Tokyo Electric Power Company, Incorporated

The Furukawa Electric Co., Ltd.

The Electric Co., Ltd.

Nozomu Matsuo

Hideyuki Omura

Yukihisa Sinoda

Yukihisa Shinoda

Takesi Kawaguchi

There is provided an optical transmission system that can identify any transmitting stations generating optical beats found within the transmission band being used for optical signals so that any degradation in the quality of the signals being transmitted and adversely affected by the optical beats may be eliminated. The light sources of the transmitting stations giving rise to the optical beats generated in the detector as a result of the differences of the wavelengths of the optical signals coming from the light sources of the transmitting stations and adversely affecting the transmission band being used for the electric signals originating the modulated optical signals are identified by changing the state of polarization of light of the optical signals coming from the light sources of the plurality of transmitting stations. In other words, the light sources of the transmitting stations that are giving rise to the optical beats adversely affecting the transmission band being used for the electric signals originating the modulated optical signals can be identified by changing the state of polarization of light of the optical signals coming from the light sources of the transmitting stations on a one-by-one basis and observing the produced optical beat at the receiving station.

Optical transmission system

There is provided a phototransmission method that can effectively avoid any deterioration by beats in the optical signal quality of a phototransmission system and transmit signals to a single receiving station with a substantially equal light intensity level even if only a narrow gap is provided for any two close wavelengths that are used for signal transmission and if the wavelength of the laser beam emitted from each semiconductor laser diode of the system is allowed to fluctuate only within a narrow limit so that the system may accommodate a large number of different light waves (transmitting stations). The light intensity level of optical signals produced at the optical output terminal of each semiconductor laser diode 3 is regulated by setting the bias current of the semiconductor laser diode 3 to a value between one and a half times and five times the threshold current of the semiconductor laser diode. Alternatively, the light intensity level of optical signals produced at the optical output terminal of each semiconductor laser diode 3 is regulated by setting the bias current of the semiconductor laser 3 to a value between twice and four times the threshold current of the semiconductor laser diode. Preferably, the light intensity levels of optical signals produced by different semiconductor laser diodes 3 of he optical transmission system are regulated by respective optical attenuators 4 operating for different degrees of attenuation.

Phototransmission method

Growing community of inventors

Yokohama, Japan

Nozomu Matsuo