Nippon Telegraph and Telephone Corporation

Hitachi Cable, Inc.

Other

The Furukawa Electric Co., Ltd.

Fujikura Limited

Ando Electric Company

Hitachi Metals, Ltd.

Toshio Kurashima

Kazuhide Nakajima

Masao Tachikura

Kazumasa Ohsono

Yoshinori Kurosawa

Eiji Araki

Tomoya Shimizu

Katumi Hiramatu

Takashi Matsui

Haruyoshi Uchiyama

Yukihiro Goto

Bing Yao

Hisanori Nakai

Takeshi Yagi

Shoichiro Matsuo

Yasushi Sato

Ryuichi Sugizaki

Shoji Tanigawa

Itaru Ishida

Naomi Kumano

Iwao Shimotakahara

Zhixien Li

Ryo Koyama

Masaaki Takaya

Kenji Kawase

Yoshikazu Namekawa

Tsuneo Horiguchi

Nobuyuki Yoshizawa

Shoji Adachi

Harumi Inaba

Kaoru Shimizu

Koushi Ishihara

Tetsuro Yabuta

Yasushi Satoh

Masatoshi Shimizu

Kyoichi Nakamizo

Hidenobu Tada

A measuring method of a longitudinal distribution of bending loss of an optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities of two backscattering light at a position x obtained by bidirectional OTDR measurement of the optical fiber; and obtaining a bending loss value at the position x from a mode field diameter 2W(x) and a relative refractive index difference &#x394;(x) at the position x calculated from the arithmetical mean value.

Measuring method of longitudinal distribution of bending loss of optical fiber, measuring method of longitudinal distribution of actual bending loss value of optical fiber, test method of optical line, manufacturing method of optical fiber cable, manufacturing method of optical fiber cord, and manufacturing method of optical fiber

A measuring method of a hole diameter of a holey optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities at a position x of two backscattering light waveforms of the holey optical fiber, in which the two backscattering light waveforms are obtained by OTDR measurement; and obtaining the hole diameter at the position x, based on a correlation between an arithmetical mean value I(x) and an hole diameter of the holey optical fiber that is obtained in advance.

Measuring method of hole diameter, hole position, hole surface roughness, or bending loss of holey optical fiber, manufacturing method of holey optical fiber, and test method of optical line of holey optical fiber

A hole-assisted optical fiber includes a core portion and a cladding portion that includes an inner cladding layer, an outer cladding layer, and holes formed around the core portion. A diameter of the core portion is 3 &#x3bc;m to 9.8 &#x3bc;m, a relative refractive index difference of the core portion relative to the outer cladding layer is 0.11% to 0.45%, an outside diameter of the inner cladding layer is 53 &#x3bc;m or less, a relative refractive index difference of the inner cladding layer relative to the outer cladding layer is a negative value, &#x2212;0.30% or more, a diameter of each hole is 2.4 &#x3bc;m to 4.0 &#x3bc;m, a hole occupancy rate is 17% to 48%, a bending loss at a wavelength of 1625 nm when bent at a radius of 5 mm is 1 dB/turn or less, and a cut-off wavelength is 1550 nm or less.

Hole-assisted optical fiber

An optical fiber which, at an optical fiber connecting end having a plurality of voids around the periphery of a core, has a light-permeable substance, such as a resin or glass whose refractive index is lower than that of quartz type substances, filled in the voids adjacent to the connecting end. An optical fiber connecting section where an optical fiber having a plurality of voids in a clad around the periphery of a core is connected to another optical fiber, wherein the optical fiber is connected end-to-end to aforesaid another optical fiber through a refractive index matching agent whose refractive index at the minimum temperature in actual use is lower than that of the core.

Method of sealing air holes in an optical fiber

An optical connector having an optical fiber inserted into a connector main body includes a buckling regulating section whose length in an optical fiber insertion direction is formed variable and which regulates a buckling of the optical fiber while becoming short in an optical fiber insertion direction when the optical fiber is inserted into the connector main body. Even if an insertion area is made long, since no buckling of the optical fiber is generated, the buckling regulating section can sufficiently increase an insertion force of the optical fiber. Thus, even when foreign substances such as dusts enter and an insertion resistance increases, the optical fiber can be securely inserted. Further, the buckling regulating section is very advantageous to realize an end surface preparation of the optical fiber making use of the insertion force of the optical fiber such as a coating removing of the optical fiber, and an end surface grinding preparation of the optical fiber.

Optical connector and method for assembling same

An optical fiber preform manufacturing method includes: supporting a drilling jig in a radial direction of a preform that is cylinder-shaped; moving the drilling jig in a longitudinal direction of the preform; and forming a plurality of slits each extending in the longitudinal direction and each directed from an outer side of the preform toward a center the preform, and a plurality of holes each extending in the longitudinal direction and each connecting with an end of one of the plurality of slits in a depth direction of the one of the plurality of slits.

Optical fiber preform manufacturing method

Optical fiber, optical fiber connecting method, and optical connector

An optical fiber coiled cord having a coil construction in which an optical fiber cord is spirally bent to obtain lengthwise stretchability, wherein the fiber coiled cord is provided with a stretch length control member which restricts lengthwise elongation.

Optical fiber coiled cord

The present invention provides an optical fiber distortion measuring apparatus and optical fiber distortion measuring method which make it possible to measure the amount of distortion of an optical fiber efficiently and in a short period of time. The time change waveform when a light pulse having a frequency of &ngr;1 is applied is compared with initial data (the time change waveform obtained in a case in which there is no distortion). Then, the light intensity L at a position Dx at which the light intensities do not agree is obtained. Next, the time change waveform is measured when a light pulse having a frequency of &ngr;2 is applied, and the light intensity L at position Dx is obtained. After this, the loss (resulting from distortion) in light intensities L and L is corrected, and light intensities LC and LC are obtained. Curve calculating unit obtains a second-order curve which is a curve resulting from the parallel movement of a curve approximating the spectrum waveform of the initial data, and which contains the (&ngr;1, LC ) and (&ngr;2, LC ) described above. The peak frequency detecting unit obtains the light frequency exhibiting a maximum value in the light intensity in the second-order curve. The distortion amount calculating unit calculates the amount of distortion based on this light frequency.

Optical fiber distortion measuring apparatus and optical fiber distortion measuring method

The present invention relates to an optical-fiber characteristics measuring apparatus that does not require frequency conversion of pulse light which enters an optical fiber to be measured, and does not restrict the cycle period of the pulse light, thereby ensuring fast measuring of the characteristics of the optical fiber. This apparatus comprises an optical directional coupler, an optical pulse generator, a balanced-light reception circuit, a signal generation section and a mixer. The optical directional coupler branches coherent light into first and second coherent lights. The optical pulse generator converts the first coherent light into pulse light which in turn enters an optical fiber to be measured. Returned light whose frequency is shifted from that of the first coherent light by a predetermined frequency through reflection and scattering in the optical fiber to be measured enters the balanced-light reception circuit. The balanced-light reception circuit carries out balanced-light reception of the second coherent light and the returned light and converts the resultant light into an electric signal. The signal generation section generates an RF signal whose frequency is equal to the predetermined frequency. The mixer mixes the electric signal and the RF signal to thereby detect the shifted frequency.

Optical-fiber characteristics measuring apparatus

An object of the present invention is to provide an optical fiber strain measuring apparatus which can perform precise measurement without causing any fluctuation in signal level. To achieve the above object the present invention comprises: a polarization plane rotation device 105 which rotates a plane of polarization of an optical pulse; a photo-directional coupler 106 which projects an optical pulse projected from the polarization plane rotation device 105 into an optical fiber 107 to be measured, and projects out backscattering light produced in the optical fiber 107 to be measured; a polarization plane rotation device 160 which rotates a plane of polarization of a reference light; a light mixing device 109 for mixing the backscattering light projected out from the photo-directional coupler 106 and the reference light projected from the polarization plane rotation device 160; and a signal processing section 111 which detects the mixed light projected from the light mixing device 109, converts the detected light into an electrical signal and subjects the electrical signal to a predetermined operational processing to obtain a measurement waveform.

Optical fiber strain measuring apparatus

Coherent light emitted from a coherent light source 1 is sent as a probe beam through a connector 31 into an optical fiber being measured. A portion of this beam is sent to an optical frequency converter 100 to form an optical pulse train having a frequency which is frequency-swept in steps of a designated frequency at a designated periodicity, and an optical pulse having a designated frequency is extracted from the optical pulse train by an electro-optic switch 18 and sent to the optical fiber being measured. Then, a signal beam exiting the optical fiber being measured is heterodyne-received by means of a local beam passing through either a connecting optical fiber 6 side or a frequency shifter 7 side according to the selection of optical switches 4 and 5. Consequently, it is possible to measure the characteristics of the optical fiber by means of a BOTDR, BOTDA or a COTDR.

Optical fiber characteristic measuring device

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

Growing community of inventors

Tokyo, Japan

Toshio Kurashima