Fujitsu Corporation

Nippon Telegraph and Telephone Corporation

Akihiko Ichikawa

Hiroshi Nishimoto

Shinya Inagaki

Kazuya Sasaki

Keiko Takeda

Katsuhiko Hakomori

Sakae Yoshizawa

Takayoshi Morita

Etsugo Yoneda

After implementing a scrambler upon an electric signal of digital signals to be transmitted to a user terminal, this electric signal is converted into a digital optical signal, and an analog optical signal and this digital optical signal are multiplexed by wavelength division multiplexing, thereby reducing influence of cross-talk interference that is exerted on the analog optical signal by the digital optical signal.

Optical transmission system and optical transmission method

With regard to an optical communications system, in a system using a single optical fiber cable between subscribers and an exchange and in which bi-directional transmission is performed using the same 1.3-.mu.m wavelength, the exchange-to-subscriber signal is a high-speed, wideband signal which is bandwidth limited by means of a lowpass filter, and the subscriber-to-exchange signal is a carrier having a frequency higher than the upper limit of the exchange-to-subscriber signal and which is modulated with a low-speed, narrowband signal.

Bi-directional optical communications subscriber transmission system

A remote light signal control apparatus is disclosed wherein the level of the light output thereof is fixed with a high degree of accuracy and, even when an ALC loop is opened, a laser diode can emit light at a stable level to assure a high degree of reliability of the laser diode. A first control section is provided in one of a light reception section and a light transmission section. The light transmission section includes a second light detection section for detecting a light emitting condition of a light source, a second control section for outputting, in response to light detection information detected by the second light detection section, a light control signal for controlling the state of a light signal from the light source, and a switch section for selectively outputting to the light source one of the light control signal from the first control section and the light control signal from the second control section with which the level of the light signal from the light source is controlled lower than that with the other.

Light signal remote control apparatus and light signal level controlling

An apparatus connects a single-mode optical fiber in a transmitting side to a multi-mode optical fiber in a receiving side without a deterioration of baseband transmission characteristics. The apparatus optically connects the single-mode fiber to the multi-mode fiber with an optical axes displacement therebetween, so that an optical signal to a multi-mode optical fiber from a single mode optical fiber is incident in a steady state mode including not only lower mode, but higher mode. In one embodiment, the optical axes displacement is achieved by axial displacement between the single-mode fiber and multi-mode fiber. In another embodiment, the optical axes displacement is achieved by an angle displacement between the single-mode fiber and multi-mode fiber.

Growing community of inventors

Kawasaki, Japan

Akihiko Ichikawa