Kokusai Denshin Denwa Kabushiki Kaisha

Kokusai Denshin Denwa Co., Ltd.

Chuichi Ota

Nobutake Imamura

Shinsuke Tanaka

Shigeyuki Akiba

Fujio Tanaka

Yasuharu Suematsu

Yoshio Itaya

Takaya Yamamoto

Kazuo Sakai

Norio Seki

Kenichi Iga

Yasuyuki Nagao

Haruo Sakaguchi

Yukitoshi Kushiro

Yotaro Yatsuzuka

Yasuyuki Okamura

Shigehisa Arai

Masanobu Kodaira

A magneto-optical recording medium, which comprises a thin film constituted of an amorphous alloy (R.sub.x TM.sub.1-x).sub.1-y A.sub.y (where the element material R is at least one rare earth element, the element material TM at least one 3d transition metal and the element material A at least one semi-metal-semiconductor element) and having an easy axis of magnetization in a direction perpendicular to the film surface, the atomic ratio being 0.15.ltoreq.xx.ltoreq.0.35 and 0.00&lt;y.ltoreq.0.20.

Magneto-optical recording medium

A magneto-optical recording medium having an easy axis of magnetization in a direction perpendicular to the film surface, characterized in that a readout medium layer, a reflection layer and a recording medium layer are sequentially disposed in a direction of the incidence of a reading-out light, thereby to increase a reproduced output.

A magneto-optical recording and reproducing apparatus for recording information on a recording medium made of a magneto-optical recording material. The apparatus is provided with at least two lasers for carrying out simultaneously a combination of two functions of the apparatus such as recording-reproducing or reproducing-erasing or erasing-recording functions. The recording and erasing is effected optically by independent light beams. Provision is made for recording and erasing the information by light beam and by use of an application of magnetic fields of different coercive values. The lasers are modulated or not independently and an optical system is provided through which the write-in and readout takes place and focusing is in response to the reflected light from the record on the recording medium.

Magneto-optical recording and reproducing system

A semiconductor laser, which comprises a substrate of InP, an active layer, and two clad layers holding therebetween the active layer, and which is constructed so that the refractive index of the active layer may be larger than the refractive indexes of the two clad layers. In one of the two clad layers, the refractive index of a region adjacent to a radiation region in the active layer is larger than the refractive index of a region adjacent to a non-radiation region in the active layer. The refractive index of the other clad layer is equal to the refractive index of that region of said on clad layer adjoining the radiation region or the non-radiation region. The thickness and width of the radiation region of the active layer are selected so that the semiconductor laser may oscillate in the fundamental transverse mode. A buffer layer may be further provided between the active layer and one of the two clad layers.

Semiconductor laser

A multi-layer magneto-optical recording medium is constructed by placing a transparent protective film upon a magneto-optical recording medium wherein the easy axis of magnetization is provided perpendicular to the film surface so as to make the direction of magnetization perpendicular thereto to take a binary code depending on whether the vertical direction thereof is upward or downward, and further by placing a metal film, of which melting point is lower than either said magneto-optical recording medium and said transparent protective film, upon said transparent protective film. The metal film is evaporated by a laser beam irradiated thereon in a manner to leave a portion thereof not evaporated to become a tracking guide, whereby reproducing a magneto-optical record free of disturbance on linear polarization. The metal film can be perforated to form pits by irradiation of a laser beam. Presence or absence of such pits can be used for storing data and, therefore, is applicable for a read-only memory of optical method or an optical video disc.

Multi-layer magneto-optical recording medium

Disclosed is a magneto-optic recording medium to which magnetic Kerr effect is applied and characterized by the tracking guide on an even surface free from disorder of linear polarization. Since the tracking guide may be any type if it has a different reflection characteristic from that of the memory area viewing from magneto-optic standpoint, the tracking guide can be produced by a thermal treatment for changing the magnetic property of a part of a thin film with its magnetization easy axis in the direction perpendicular to the film surface. As no difference exists between the memory area and the guide area other than their magnetic properties, they are on the same plane and have no unevenness between their surfaces. Where, the guide area is assumed to have such magnetic property as the magnetization easy axis is parallel to the film surface, or it is perpendicular to the film surface but has no rectangular hysterisis. Such change of magnetic property can be obtained easily by an irradiation of laser beam to an amorphous alloy thin film with perpendicular magnetization easy axis.

Magneto-optic recording medium

A semiconductor laser having a multi-layer film which is inclusive of an active layer and formed on an InP substrate, in which at least one layer adjacent to the active layer is formed of a material which is a composition having a larger band gap than InP and whose component ratio is so selected as to match with the lattice constant of InP, thereby to ensure that minority carriers injected into the active layer efficiently contribute to laser operation. The material has a composition including at least three elements in addition to InP.

A semiconductor laser formed on an InP substrate to have a hetero structure comprising a plurality of In.sub.1-x Ga.sub.x`As.sub.y P.sub.1-y (0.42y.ltoreq.x.ltoreq.0.5y,0.ltoreq.y.ltoreq.1) layers which are lattice-matched with InP, in which a light emitting layer included in the layers and having a forbidden band width larger than 0.6 eV but smaller than 0.9 eV at room temperature is sandwiched between two InP layers on the InP substrate, and in which there is provided between the light emitting layer and the InP layer grown thereon at least one buffer layer having a forbidden band width larger than the forbidden band width of the light emitting layer but smaller than the forbidden band width of InP. The forbidden band width of the buffer layer at room temperature may be larger than 0.8 eV but smaller than 1.0 eV.

Semiconductor laser with buffer layer

A fault location system in an optical fiber transmission system, in which a plurality of optical signal regenerative repeaters are sequentially connected in cascade in an optical fiber transmission cable at predetermined intervals to transmit digital information in the form of optical signals. Each of the plurality of optical signal regenerative repeaters sends out a fault location information signal composed of an inherent pattern and a fixed pattern when a fault occurs in the corresponding repeater. The inherent pattern is uniquely assigned to the optical signal regenerative repeater from a plurality of individually distinguishable inherent patterns obtained by establishing the start bits of a pseudo-noise sequence at time positions successively delayed from one after another. The fixed pattern is necessary for indicating the time positions of the start bits. A malfunction position in the optical fiber transmission system can be detected by detecting the fault location information signal at a monitor station in the optical fiber transmission system.

Fault locating system in optical fiber transmission system

A system for transmitting a coded voice signal representative of an original analogue voice signal, for improved performance in time assignment multiplex systems. A voice signal detector detects when the magnitude of the coded voice signal exceeds a certain predetermined value which corresponds to the presence of an original voice signal. A waveform analyzer estimates high frequency components of the original voice signal and the detected coded voice signal is transmitted at intervals determined by the measured values of the high frequency components. The transmitted coded voice signal is comprised of digital code units, and the number of bits in each code unit are reduced at low transmission speed by distributing the bits of the code units between more than one transmission interval.

System for transmitting a coded voice signal

A wide-band hybrid network, in which a signal received from a four-wire section is applied to a first balanced amplifier and a second balanced amplifier. The output of the first balanced amplifier is applied to one opposed terminals of a main bridge circuit which has an arm including terminals connected to a wide-band two-wire transmission line. The output of the second balanced amplifier is applied to one opposed terminals of an auxiliary bridge circuit which has an arm substantially equivalent to the impedance of the wide-band two-wire transmission line. A differential amplifier is employed for receiving signals of respective other opposed terminals of the main bridge circuit and the auxiliary bridge circuit. The output of the differential amplifier is applied to another four-wire section.

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Fuchu, Japan

Chuichi Ota