Nippon Telegraph and Telephone Corporation

Ando Electric Company

Tsuneo Horiguchi

Nobunari Takeuchi

Kaoru Shimizu

Tekken Lee

Haruyoshi Uchiyama

Mitsuhiro Tateda

Yahei Koyamada

Toshiya Sato

Toshio Kurashima

Nobuyuki Yoshizawa

Mikio Maeda

Koushi Ishihara

Tetsuro Yabuta

Tatsuyuki Fujita

Tekken Ri

Satohi Matsuura

Hidenobu Tada

The present invention provides light frequency control apparatus comprising a light pulse signal generating mechanism for generating a light pulse signal of a standard frequency; a light frequency shifting mechanism for circulating this light pulse signal a predetermined number of times, delaying this light pulse signal at each cycle thereby sequentially shifting and outputting the aforementioned light pulse signal; an extracting mechanism for extracting a light pulse signal in the second half of a cycle from the output of the light frequency shifting mechanism; and a polarization control mechanism inserted into the light frequency shifting mechanism for controlling the angle of polarization of the light pulse signal circulating in the light frequency shifting mechanism based on the amount of attenuation of the light pulse signal outputted by the extracting mechanism.

Light frequency control apparatus

The present invention provides light frequency control apparatus comprising a light pulse signal generating mechanism for converting continuous light into a light pulse signal, and outputting this light pulse signal; a light signal generating mechanism for repeatedly generating at predetermined cycles, a light signal, in which a light frequency component therein is shifted to form a staircase shape based on the number of cycles of a loop within which the light pulse signal circulates; and a dummy light generating mechanism for generating dummy light at a timing such that the level of the light signal becomes zero, and supplying this dummy light to the light amplifying mechanism. The aforementioned loop is formed from a light amplifying mechanism for amplifying the light pulse signal outputted from the light pulse signal generating mechanism, light delay mechanism for delaying the light pulse signal a fixed amount; and frequency shifting mechanism for shifting the frequency of the light pulse signal.

A reference light generating mechanism generates reference light, a light frequency component of which varies in a stepped manner at fixed intervals, repeatedly at pre-specified cycles, and generates a timing signal in accordance with this variance. A detecting mechanism detects a frequency difference between a reference light frequency freely selected from among the light frequency component and a feedback light frequency of feedback light fed back so as to conform to the reference light frequency, and synchronizes this with a timing signal, and an output light generating mechanism generates output light, the light frequency of which is controlled in accordance with the frequency difference, and conducts the feedback of this output light to the detecting mechanism as feedback light.

Light frequency synthesizer

A light frequency shifter repeatedly generates, at predetermined cycles, an optical signal, an optical frequency component of which varies in a stepped manner at fixed intervals, and timing generating circuit generates timing signals corresponding to this variation. Detecting mechanisms synchronize, with the timing signal, a frequency difference between a reference light frequency freely selected from the light frequency component and a feedback light frequency of feedback light fed back so as to conform to this reference light frequency, and detect this. Light frequency-regulated light source extracts an output optical signal circulating within a closed loop circuit controlling the light frequency in accordance with the frequency difference described above, and supplies this to a light output terminal, and feeds back a portion of the output optical signal to the detecting mechanism as the feedback light described above.

Light-frequency control apparatus

An apparatus for measuring a distortion position of an optical fiber is disclosed. A light source generates continuous light with frequency f.sub.0 and injects the continuous light into a far-end of an optical fiber to be measured. An optical coupler divides the outgoing continuous light from a near-end of the optical fiber. An optical amplifier amplifies output light from the optical coupler. A first optical switch generates a first optical pulse by switching output light from the optical amplifier. An optical frequency shifter generates a second optical pulse having frequency components (f.sub.0 +f.sub.m) based on the first optical pulse from the first optical switch. A second optical switch injects the second optical pulse into the near-end of the optical fiber. A display displays outgoing continuous light with frequency f.sub.0 from the near-end of the optical fiber via the optical coupler and the second optical switch. A timing control circuit controls the operation timing of the first and second optical switches and the optical frequency shifter.

Apparatus for measuring distortion position of optical fiber

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 light source which is stabilized in frequencies at uniform intervals comprises a light source 5 whose light frequency is varied with a signal from a reference signal source 4; a frequency detector 6 for detecting the frequency of the output of the light source 5, the cycles of the said frequency detector being the same as the uniform intervals; a comparator 2 for comparing the output of the frequency detector 6 and the output of the reference light source 1; and a switch 3 having as its input the output of the comparator 2 for inputting the output to the light source 5, said switch being so operated that when the frequency of the light source 5 is to be changed the switch is opened and the output of the reference signal source 4 is changed to set the output frequency of the light source 5 near the desired frequency and then the switch 3 is closed.

Frequency stabilized light source

An optical cable has a center member, around which a plurality of coated optical fibers are tightly stranded. Each optical fiber is given uneven strains in its longitudinal direction. Adhesive resin is applied to surround each of the coated optical fibers and binds each of them to the center member to make an integral optical unit when cured.

Optical cable and its manufacturing method

Use is made of a non linear interaction between a first modulated signal light from a first light source and a second signal light from a second light source which propagate in an optical fiber to be examined in opposite directions, i.e., so-called Brillouin light amplification, to analyze the signal waveform of the second signal light, which is influenced by the action of such light amplification.

Growing community of inventors

Mito, Japan

Tsuneo Horiguchi