Ando Electric Company

Nippon Telegraph and Telephone Corporation

Nippon Hoso' Kyokai

Mikio Maeda

Toshiya Sato

Tsuneo Horiguchi

Shinichi Furukawa

Masaaki Furuhashi

Tadasu Ishikawa

Kimiyuki Oyamada

Tatsuyuki Fujita

Yozo Utsumi

Kunihara Takizawa

Mitsuhisa Sato

Shuichi Fujisawa

An optical masking apparatus of an OTDR capable of lowering insertion loss and of easily aligning optical axes and of being structured at low cost. The apparatus comprises an optical pulse generating means, an optical branching coupler for permitting an optical pulse generated by the optical pulse generating means to be incident to an optical fiber to be measured, and an optical chopper means to which a reflected light from the optical fiber is incident by way of the optical branching coupler wherein the optical chopper means operates in synchronization with the optical pulse to remove a desired range of the reflected light. A light signal supplied to an optical/electric transducer from the optical chopper means is converted into an electric signal, which is displayed on an indicator by way of a signal processing circuit.

Optical masking apparatus

The purpose of the present invention is to provide a time domain reflectometer in which the system cost is low and the dynamic range is wide. In accordance with the present invention, an excitation light source for generating continuous light of a predetermined frequency (e. g., 1.48 .mu.m), and a ring laser part for generating a high power light pulse in accordance with the continuous light are provided. A light branch device is held in common by the ring laser part and a measurement part. The light branch device makes the light pulse which has been incident on one of its end parts to be incident on a light cable to be measured; and the light branch device also receives response light and supplies the response light to a light receptor in the measurement part. In the measurement part, the response light is converted to a corresponding electric signal and the signal is amplified to be supplied to a measurement circuit.

Optical time domain reflectometer using ring laser light source

An optical pulse tester capable of displaying Raman scattered light is disclosed. An optical pulse with the specified wavelength is injected into an optical fiber to be measured via a directional coupler and an optical demultiplexer/multiplexer. The demultiplexer/multiplexer demultiplexes returning light from the optical fiber into Raman scattered light different from the optical pulse in wavelength. The directional coupler divides returning light from the optical fiber into Fresnel reflection light and Rayleigh scattered light with the specified wavelength. The switcher supplies the Rayleigh scattered light to a display In the case of long distance measurement or precise loss measurement of the optical fiber. Therefore, the display displays the characteristic waveform of the optical fiber with the Rayleigh scattered light. In contrast, the switcher supplies the Raman scattered light to the display in the case of the measurement of the near-end part of the optical fiber or the connecting point between optical fibers without a dead area. Therefore, the display displays the characteristic waveform of the optical fiber with the Raman scattered light.

Optical pulse tester capable of displaying Raman or Rayleigh scattered

A bidirectional light transmission system comprises a transmitting station having a light source for intensity-modulating a transmission signal, a first light branching portion for branching intensity-modulated light of the light source in a predetermined ratio and a first light receiving portion, and a receiving station having a second light branching portion, a light phase-modulating portion, a light reflecting portion and a second light receiving portion. The transmitting station transmits the intensity-modulated light via a single optical fiber transmission line to the receiving station connected thereto and receives a returned signal returned from the receiving station via the single optical fiber transmission line in the first light receiving portion, and the receiving station branches the transmitted light into first branched light and second branched light in the second light branching portion, phase-modulates at least one of the first branched light and second branched light in the light phase-modulating portion, transmits part of the first branched light and second branched light to the second light receiving portion via the light reflecting portion and simultaneously intensity-modulates reflected part of the first branched light and second branched light as a returned signal in the light phase-modulating portion and the second light branching portion, and returns the returned signal to the transmitting station via the single optical fiber transmission line.

Bidirectional light transmission system and optical device therefor

Growing community of inventors

Tokyo, Japan

Mikio Maeda