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1. 发明专利

JPH0325987A SEMICONDUCTOR LASER LIGHT SOURCE 失效
公开(公告)号：JPH0325987A
公开(公告)日：1991-02-04
申请号：JP15943489
申请日：1989-06-23
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： RYU SHIRO , MOCHIZUKI KIYOBUMI , WAKABAYASHI HIROHARU
IPC分类号： H01S5/00 , H01S3/107 , H01S5/12 , H01S5/14
摘要： PURPOSE:To provide a narrow spectrum beam width and to provide flat and wide band frequency modulation characteristic by frequency-modulating with an external resonator in which one side face of a light phase modulator for varying a refractive index by the application of a voltage is covered with a high reflectivity coating, and modulating means for modulating the applied voltage. CONSTITUTION:A rearward emitting light L2 emitted rearward from a semiconductor laser 1 for emitting forward an output light L1 is introduced to an external resonator 20, i.e., a ferrodielectric light phase modulator 16 through a lens 2, reflected on a high reflection coating film 19 formed on the one side face of the modulator 16, returned as a return light L2 from the resonator 20 to the laser 1, thereby realizing a narrow spectrum beam width. The phase of the light in the resonator 20 is varied by a data signal E1 applied to the electrode 13 of the modulator 16, thereby varying the frequency of the light L1 emitted from the laser 1.

2. 发明专利

JPH0321933A OPTICAL AMPLIFIER MODULE 失效
公开(公告)号：JPH0321933A
公开(公告)日：1991-01-30
申请号：JP15558689
申请日：1989-06-20
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： YAMAMOTO SHU , MOCHIZUKI KIYOBUMI , WAKABAYASHI HIROHARU , TAGA HIDENORI
IPC分类号： G02F1/35
摘要： PURPOSE:To provide a nearly constant amplification gain irrelevantly to the polarized state of a light signal by arranging a polarizing element which makes a 90 deg. polarization rotation between a 1st and a 2nd optical amplifier which differ in amplification gain. CONSTITUTION:Two optical amplifiers are used and arranged in series, and the polarizing element providing 90 deg. polarization rotation is interposed between them. Consequently, signal light L1 which is incident by its TE polarized wave to, for example, an optical amplifier 12A is provided with the TE gain GTE1 of the optical amplifier 12a, then whose polarization is rotated by 90 deg. through a 1/2-wavelength plate 13, so a TM polarized wave is made incident on a 2nd- stage optical amplifier 12a, then a TM gain GTM2 is provided, so that the total amplification gain comes to GT. When the signal light L1 is incident in TM mode on the optical amplifier 12a, on the other hand, the light is provided with the TE gain GTM1 by the optical amplifier 12a and the TM gain GTE2 by the optical amplifier 12b, so that the total gain is the same GT with the TE polarized wave input. The nearly constant gain GT is obtained by the amplifiers on the whole for an optional incident polarized wave.

3. 发明专利

JPH02119328A MONITORING CONTROL SYSTEM FOR OPTICAL REPEATER 失效
公开(公告)号：JPH02119328A
公开(公告)日：1990-05-07
申请号：JP27072988
申请日：1988-10-28
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： YAMAMOTO SHU , MOCHIZUKI KIYOBUMI , WAKABAYASHI HIROHARU , TAGA HIDENORI
IPC分类号： H04B10/29 , H01S3/067 , H01S3/094 , H01S3/13 , H01S3/131 , H01S5/0683 , H01S5/50 , H04B10/032 , H04B10/035 , H04B10/07 , H04B10/077 , H04B10/079 , H04B10/293 , H04B10/297 , H04B10/54 , H04B10/564
摘要： PURPOSE:To keep the gain of a semiconductor light amplifier used in an optical repeater by modulating the intensity of signal light with a modulation index less than a signal bit rate frequency by a sine wave of low frequency, and using the signal as a control monitoring signal. CONSTITUTION:An optical demultiplexing circuit 2 demultiplexes the partial demultiplex light L3 of output amplification light L2 from the semiconductor light amplifier, and an optical/electrical (O/E) conversion circuit 4 outputs to convert it to an electrical signal S1. The amplification light L2 outputted from the light amplifier 2 is comprised of amplified signal light and natural emission light L0 which becomes noise light generated from the semiconductor light amplifier 2. The intensity of the amplified signal light is modulated by the sine wave of low frequency, however, no modulation is applied on the natural emission light L0. Therefore, the output signal S2 of a filter 5 is obtained as the sine wave for control in proportion to the signal light L1. The gain can be kept constant by detecting the fluctuation of the gain of the semiconductor light amplifier 2 from the fluctuation of the output signal S2 of the filter 5, and controlling an injection current Ii by an amplifier driving circuit 7 receiving a driving control signal S3 from an automatic gain control(AGC) circuit 6 so as to keep the level of the sine wave constant.

4. 发明专利

JPH0227781A METHOD AND APPARATUS FOR STABILIZING AND CONTROLLING FREQUENCY OF SEMICONDUCTOR LASER LIGHT SOURCE 失效
公开(公告)号：JPH0227781A
公开(公告)日：1990-01-30
申请号：JP17715188
申请日：1988-07-18
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： MIYAZAKI TETSUYA , MOCHIZUKI KIYOBUMI , RYU SHIRO
IPC分类号： H01S5/068 , H01S5/0683 , H01S5/0687
摘要： PURPOSE:To eliminate an error due to a light intensity variation and to measure an accurate frequency variation by suppressing the light intensity variation of a monitoring light radiated rearward from a laser light source by a light intensity variation suppressor, and feeding it to a frequency variation detector. CONSTITUTION:A monitoring branched light ML1 having a predetermined light intensity level by a light intensity variation suppressor C on the basis of the monitoring branched light ML2 is frequency variation/light intensity-converted by a light frequency discriminator 4, and input to a photodetector 5. A differential amplifier 9 obtains a differential voltage V9 between a reference voltage V8 corresponding to a predetermined frequency output from a constant-voltage circuit 8 and a frequency variation signal V5. The voltage V9 is fed to a controller B for controlling the injected current or temperature of a laser light source 1. Thus, an error due to the light intensity variation is eliminated, and an accurate frequency variation measurement can be performed.

5. 发明专利

JPH022228A MONITOR SYSTEM AND APPARATUS FOR LONG RANGE OPTICAL COMMUNICATION SYSTEM 失效
公开(公告)号：JPH022228A
公开(公告)日：1990-01-08
申请号：JP14323988
申请日：1988-06-10
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： WAKABAYASHI HIROHARU , MOCHIZUKI KIYOBUMI , YAMAMOTO SHU , EDAKAWA NOBORU
IPC分类号： H04B10/035 , H04B10/07 , H04B10/071 , H04B10/077 , H04B10/29 , H04B10/297 , H04B17/40
摘要： PURPOSE:To monitor level diagrams of an optical communication system being a broken pint of an optical fiber or the operating state of an optical repeater simply and simultaneously by measuring a timewise behavior change of a backward scattered light. CONSTITUTION:An output of an incoming optical repeater 5a is sent to an optical fiber 1b via an optical branch circuit 7 and a backward scattered light caused in the optical fiber 1b or a reflected light caused at a faulty point 11 is led to an optical switch circuit 10 via the optical branch circuit 7 again. The backward scattered light via the optical switch circuit 10 is led to an outgoing optical repeater 6a by an optical synthesis circuit 8 and sent to a land station via the fiber 2b. The timewise behavior change of the level of the backward scattered light is checked by the land station to monitor a broken (fault) point or the like.

6. 发明专利

JPH01224732A OPTICAL AMPLIFYING SYSTEM FOR LONG-DISTANCE OPTICAL COMMUNICATION SYSTEM 失效
公开(公告)号：JPH01224732A
公开(公告)日：1989-09-07
申请号：JP4971888
申请日：1988-03-04
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： MOCHIZUKI KIYOBUMI , EDAKAWA NOBORU , YAMAMOTO SHU , WAKABAYASHI HIROHARU
IPC分类号： G02F1/35 , H04B10/2537 , H04B10/29 , H04B10/291
摘要： PURPOSE:To constitute a long-distance optical communication system by providing a polarization compensating means which sets the plane of polarization of an optical signal to a preliminarily determined polarization state and an analyzer whose axis of polarization coincides with the plane of polarization of the optical signal in the preliminarily determined polarization state and reducing spontaneous emission light from an optical amplifier. CONSTITUTION:An analyzer 8 is inserted and arranged between an optical filter 7 and a photodetector 6 so that the axis of polarization coincides with the plane of polarization of the signal light. When the signal light is so controlled by a polarization compensator 2 that signal light L from an optical amplifier 4 is the linearly polarized light and the analyzer 8 is so arranged that its axis of polarization coincides with the plane of polarization of the signal light L, the analyzer 8 does not attenuate the signal light L and is transparent to this light. On the other hand, the spontaneous emission light from the optical amplifier 4 is the non-polarized light having equal power for all planes of polarization, and therefore, the overall power of the spontaneous emission light is attenuated when this light passes the analyzer 8. Thus, the level of the spontaneous emission light is reduced in comparison with a conventional system, and an optical amplifying system of the long-distance optical communication system where the spontaneous emission light is reduced to perform communication is obtained.

7. 发明专利

JPH01114832A POLARIZED WAVE DIVERSITY LIGHT RECEIVING SYSTEM BY BASE BAND SYNTHESIZING METHOD 失效
公开(公告)号：JPH01114832A
公开(公告)日：1989-05-08
申请号：JP27036787
申请日：1987-10-28
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： RYU SHIRO , MOCHIZUKI KIYOBUMI
IPC分类号： H04B10/516 , G02F2/00 , H04B10/07 , H04B10/61
摘要： PURPOSE:To improve the stability of a system and to obtain satisfactory receiving sensitivity by constituting the control signal of a local oscillation laser so as to become equivalently the sum of a square value of a receiving signal and executing the IF stabilization in a polarized wave diversity light receiving system. CONSTITUTION:An IF stabilizing circuit 20 is constituted by connecting suitable weighting circuits 6c, 6d to the outputs of frequency discriminators 10a, 10b, so that its output obtains the sum of a square value of an output voltage of optical receivers 5a, 5b. Accordingly, the receiving signal being the sum of the square value which has been obtained becomes a signal which depends on a frequency but does not depend on a polarized wave state and inputted to a control circuit 11, and constituted so as to control the frequency of a local oscillation laser 2 by the control signal being its output. In such a way, the IF stabilization having no relation to a polarized wave state of a signal light 1 can be executed, and satisfactory light receiving sensitivity can be obtained.

8. 发明专利

JPS6427329A FAULT LOCATION SUPERVISORY SYSTEM FOR OPTICAL FIBER COMMUNICATION SYSTEM 失效
公开(公告)号：JPS6427329A
公开(公告)日：1989-01-30
申请号：JP18224387
申请日：1987-07-23
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： MOCHIZUKI KIYOBUMI , EDAKAWA NOBORU , IWAMOTO YOSHINAO
IPC分类号： H04B17/40 , H04B10/035 , H04B10/07 , H04B10/077 , H04B10/297
摘要： PURPOSE:To accurately supervise the faulty location of bidirectional optical transmission system by supervising each supervisory signal in the bidirectional optical transmission system using a bidirectional optical amplifier. CONSTITUTION:An optical signal having a frequency f1 is transmitted from the side A. The optical signal is demultiplexed by an optical demultiplexer 1-3, the one signal passes through an optical filter 1-5 enabling to pass the optical signal of the frequency f1 only and is coupled with a main line optical fiber 1-2 by an optical multiplexer 1-4 and looped back to the side A through an optical amplifier 1-7. Moreover, an optical signal of a frequency f2 is transmitted from the side B. The optical signal is multiplexer 1-4 and the one passes through an optical filter 1-6 enabling to pass the optical signal of the frequency f2 only and is coupled with a main line optical fiber 1-1 by an optical filter 1-3, passes through the optical amplifier 1-7 and looped back to the side B. In selecting the frequencies f1, f2 of the supervisory optical signal to frequencies different from the frequency of a communication optical signal, the presence and absence of a fault in the optical amplifier 1-7 and the optical cable are supervised without giving effect on the communication optical signal.

9. 发明专利

JPS6374332A POLARIZED WAVE DIVERSITY OPTICAL RECEPTION SYSTEM 失效
公开(公告)号：JPS6374332A
公开(公告)日：1988-04-04
申请号：JP21806286
申请日：1986-09-18
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： RYU SHIRO , MOCHIZUKI KIYOBUMI , EDAKAWA NOBORU
IPC分类号： H04B10/61 , G02F2/00 , H04B10/00 , H04B10/2507 , H04B10/516
摘要： PURPOSE:To improve the reliability and to decrease the loss of a signal light by synthesizing a signal light of optional polarized wave and a local oscillation light of circularly polarized wave, separating them into orthogonal linear polarized wave and detecting it and connecting optical elements by an optical fiber to be connected while the plane of polarization is maintained. CONSTITUTION:The light of a signal laser 1 is propagated through the optical fiber 2 and made incident in an optical fiber pi/2 phase shift coupler 13 in an optional polarized wave state. Then the local light having a linearly polarized wave in a fixed direction from the local oscillation laser 5 is subject to rotation of polarized direction so as to be made coincident with the specific direction of the coupler 13 while preserving the polarized wave front by a plane of polarization preserving optical fiber 14-1 and made incident in the coupler 13. The said signal light and local light are led to a polarized demultiplex element 3 via a single mode optical fiber 17, demultiplexed into orthogonal polarized components and made incident in the optical receivers 8a, 8b. Moreover, the plane of polarization preserving optical fibers 14-1, 14-2, 14-3 and the laser 1 are connected between the laser 1 and the coupler 13, between a laser 5 and the coupler 13, between the element 3 and the receiver 8a and between the element 3 and the receiver 8b to improve the reliability of the system. Since the polarized wave of the light is the circularly polarized wave at the emitting end of the coupler 13, even if the element 3 give demultiplexing to the orthogonally polarized wave, the polarization is made coincident with the orthogonal polarized component of the signal light without fail, and no loss is given to the signal light.

10. 发明专利

JPS6374331A DIVERSITY OPTICAL RECEPTION SYSTEM 失效
公开(公告)号：JPS6374331A
公开(公告)日：1988-04-04
申请号：JP21806586
申请日：1986-09-18
申请人： KOKUSAI DENSHIN DENWA CO LTD
发明人： RYU SHIRO , MOCHIZUKI KIYOBUMI , EDAKAWA NOBORU
IPC分类号： H04B10/00 , H04B7/10 , H04B10/25 , H04B10/516 , H04B10/61
摘要： PURPOSE:To obtain nearly the same code error rate as that of a conventional system without using any weighting circuit by using a square detector as a demodulator so as to use the demodulation function and the weighting function in common in the polarized wave diversity and phase diversity optical reception. CONSTITUTION:The demodulator 110 consists of a diode 111 having a square detection characteristic, a coil 112 applying a zero potential to the anode of the diode 111 in terms of DC to form a bias voltage supply circuit, a bias voltage application terminal 113 applying a bias voltage, a bias voltage control resistor 114 and a load resistor 115. As the demodulator 110 arranged between an equalizer 10 and a synthesizer 12, the said square detector is used and a voltage operated by the square detection by the voltage-current characteristic of the diode 111 is applied to the terminal 113. Thus, the demodulator 110 has a similar weighting function to that of a conventional system in addition to the demodulation function. In using the demodulator 110 by the square detection, the demodulation and weighting functions are applied at the same time. Thus, the device is simplified without using any weighting circuit.

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