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1. 发明专利

JP2002232048A OPTICAL AMPLIFIER 失效
公开(公告)号：JP2002232048A
公开(公告)日：2002-08-16
申请号：JP2001023370
申请日：2001-01-31
申请人： FUJITSU LTD
发明人： HAYASHI ETSUKO , SUGAYA YASUSHI , ONODA YOSHITO , SASAKI KEIKO
IPC分类号： H01S3/131 , H01S3/06 , H01S3/067 , H01S3/094 , H01S3/10 , H04B10/077 , H04B10/079 , H04B10/2507 , H04B10/29 , H04B10/296 , H04J14/00 , H04J14/02 , H04B10/16 , H04B10/17
摘要： PROBLEM TO BE SOLVED: To suppress the variation in output of an optical amplifier used in a wavelength division multiplex optical transmission system. SOLUTION: An inputted signal light (wavelength multiplexed light) is introduced by an EDF 1. Excited lights generated in exciting light sources 2 and 3 are fed to the EDF 1. A dummy light source 11 generates a dummy light. The dummy light is introduced by the EDF 1. The dummy light has a wavelength shorter than that of a band allocated to the signal light.

2. 发明专利

JPH03220467A METHOD AND APPARATUS FOR MEASURING CHARACTERISTIC OF PHOTO DETECTOR 失效
公开(公告)号：JPH03220467A
公开(公告)日：1991-09-27
申请号：JP1478590
申请日：1990-01-26
申请人： FUJITSU LTD
发明人： KIYONAGA TETSUYA , CHIKAMA TERUMI , ONODA YOSHITO
IPC分类号： G01R31/26 , G01J1/00 , G01M11/00 , G01R29/26 , H01L21/66
摘要： PURPOSE:To establish a handy measuring method and attain a lower cost by measuring an output noise power of a photo detector to be measured into which light is inputted from a semiconductor light amplifier under individual bias currents to determine a Y factor. CONSTITUTION:First, output noises of a photo detector 3 for calibration and a photo detector 4 to be measured are measured by switching a bias current of a bias circuit 2 and a switch 30 and a noise faitor NF is determined by performing a specified computation. Then, by the same switching operation, a transimpedance Zr is determined by a specified computation. Then, these noise index NF and transimpedance Zr are determined for each band width (frequency band width selected with a frequency selection level meter 5) and an input converted noise determined at each band width is shown on a display device 31 thereby enabling the obtaining of a frequency characteristic of the input converted noise automatically and in a short time.

3. 发明专利

JPH0353726A BROAD BAND OPTICAL RECEIVER 失效
公开(公告)号：JPH0353726A
公开(公告)日：1991-03-07
申请号：JP18960489
申请日：1989-07-21
申请人： FUJITSU LTD
发明人： KIYONAGA TETSUYA , ONODA YOSHITO , CHIKAMA TERUMI , WATANABE SHIGEKI , NAITO TAKAO
IPC分类号： H03H7/075 , H03F3/60 , H04B10/40 , H04B10/50 , H04B10/60 , H04B10/64
摘要： PURPOSE:To realize low noise and broad band performance simultaneously by interconnecting a photodetector and a distributed type amplifier circuit and amplifier elements in the inside of the distributed type amplifier circuit with a constant K-type filter. CONSTITUTION:A cathode of a photodetector 1 connects to an input terminal of a distributed type amplifier 4 via a series capacitor 2 and an inductance element 3. The input side circuit of the distributed type amplifier 4 consists of cascade connection of constant K-type filters each comprising a T-circuit making up of a gate-source capacitance Cgs of a transistor(TR) 41 and inductive components L/2 of two inductance elements 42 and the output side circuit consists of cascade connection of constant K-type filters each comprising a T-circuit making up of a drain-source capacitance Cds and a drain-source resistance Rds of a transistor(TR) 41 and inductive components L/2 of two inductance elements 43. Thus, the amplifier elements are matched and broad band processing is attained.

4. 发明专利

JPH0321126A DIRECT FREQUENCY MODULATION PSK SYSTEM 失效
公开(公告)号：JPH0321126A
公开(公告)日：1991-01-29
申请号：JP15466489
申请日：1989-06-19
申请人： FUJITSU LTD
发明人： NAITO TAKAO , CHIKAMA TERUMI , WATANABE SHIGEKI , KIYONAGA TETSUYA , ONAKA HIROSHI , ONODA YOSHITO
IPC分类号： H01S3/10 , H04B10/516 , H04B10/556 , H04B10/61 , H04L27/20 , H04L27/22 , H04L27/227 , H04L27/233
摘要： PURPOSE:To suppress the dispersion of wavelength and to attain the regeneration of a carrier signal by proving a driving part to modulate an optical oscillation part and oscillation frequency and adjusting the amount and time required for a frequency deviation so that a phase deviation between codes goes to pi. CONSTITUTION:A driving circuit 12 for directly modulating a transmission light source 11 using a semiconductor laser (LD) adjusts the frequency deviation amount and a frequency deviation time so that the phase deviation between different codes goes to pi based upon an input signal. Light modulated at its frequency is transmitted to the reception side through a transmission line 13. The transmitted light is multiplexed with locally oscillated light from a local oscillation light source 15 constituted of an LD to be oscillated at its fixed amplitude and frequency by means of a photocoupler 14. The multiplexed light is converted into an electric signal through a photodetector 16 and a generated intermediate frequency signal is inputted to a demodulator 17 and branched. One of the branched signals is delayed only by one time slot with a delay circuit 18, the other branched signal and the delayed signal are remixed by a mixer 19 to reproduce and output transmission information.

5. 发明专利

JPH02167508A STRUCTURE OF FRONT END OF OPTICAL FIBER 失效
公开(公告)号：JPH02167508A
公开(公告)日：1990-06-27
申请号：JP10461889
申请日：1989-04-26
申请人： FUJITSU LTD
发明人： OIKAWA YOICHI , MORI KAZUYUKI , MIYATA HIDEYUKI , NAITO TAKAO , NAKAMOTO HIROSHI , ONODA YOSHITO
IPC分类号： G02B6/42
摘要： PURPOSE:To provide sufficient latitude to optical coupling to a photodetector and to enhance optical coupling efficiency by setting the radius of a hemispherical shape and the angle of a polished surface in such a manner that the light reflected on the polished surface is outputted with the max. efficiency in the hemispherical part of the front end part. CONSTITUTION:An optical fiber 100 having a core 200 along the central axis is tapered in the prescribed length from the front end part thereof until the diameter of the section perpendicular to the central axis at the front end attains a prescribed size. The front end part is worked at the prescribed radius to the hermispherical shape and is subjected to surface polishing to the position which forms a prescribed angle with the central axis from the prescribed part at the front end and where the total section of the core appears. Namely, the light signal transmitting in the optical fiber 100 changes the optical path in the polished part and the exit light is converged by the lens effect of the part worked to the hermispherical shape at the front end and arrives at the light receiving surface of the photodetector 300. Since the light signal arrives at the light receiving surface in such a manner without spreading, the latitude increases and the high optical coupling efficiency is obtd. with a small light receiving surface.

6. 发明专利

JPS6451733A FREQUENCY MULTIPLEX OPTICAL COMMUNICATION SYSTEM 失效
公开(公告)号：JPS6451733A
公开(公告)日：1989-02-28
申请号：JP20846887
申请日：1987-08-21
申请人： FUJITSU LTD
发明人： ONODA YOSHITO , CHIKAMA TERUMI , KIYONAGA TETSUYA
IPC分类号： H04J14/00 , H04J14/02
摘要： PURPOSE:To attain long range transmission by providing a network equalizer cancelling the transmission loss varied with a signal optical frequency between an optical transmission line and an optical receiver. CONSTITUTION:Signal lights of plural optical transmitters 1 with different frequency are multiplexed and the result is sent to an optical transmission line 2 and the optical receiver 3 receives the signal light sent via the line 2 with demultiplexing. A network equalizer 4 amplifying or attenuating the signal light to cancel the difference from the transmission loss caused by the change in the transmission loss of the optical transmission line 2 depending on the frequency of the signal light is provided between the optical transmission line 2 and the optical receiver 3. Thus, the signal light level inputted to the optical receiver 3 is made constant independently of the frequency and the limit of the transmission distance extension caused by the deviation from the permissible input range of the optical receiver 3 is excluded.

7. 发明专利

JPS6424481A OPTICAL FREQUENCY MODULATION SYSTEM 失效
公开(公告)号：JPS6424481A
公开(公告)日：1989-01-26
申请号：JP18053687
申请日：1987-07-20
申请人： FUJITSU LTD
发明人： CHIKAMA TERUMI , KIYONAGA TETSUYA , ONODA YOSHITO
IPC分类号： H04B10/00 , H01S5/06 , H01S5/062 , H01S5/14 , H04B10/548 , H04B10/58
摘要： PURPOSE:To reduce distortion in a modulated wave form and to improve device reliability by a method wherein a bias current is changed in a semiconductor laser device provided with an external cavity for the production of mode hopping for discontinuous change in the oscillation frequency. CONSTITUTION:In a semiconductor laser device 1 equipped with an externally installed cavity, a portion of light emitted by the laser device 1 is reflected by a reflector 2 before being fed back to the laser device 1. A bias current for the laser device 1 is caused to change for the production of mode hopping, which subjects the oscillation frequency to a change that is not continuous. In this design, different from a design wherein change in the oscillation frequency takes place continuously in response to a change in a semiconductor laser bias current, a modulated wave form is prevented from distortion and the reliance of the modulated wave form upon an inputted wave form is reduced. In addition, a great change in frequency may realize in the presence of a very small change in a current. A heterodyne receiving circuit may be simplified, which improves the circuit in reliability.

8. 发明专利

JPS6416036A AUTOMATIC RECEPTION LEVEL CONTROL SYSTEM FOR COHERENT LIGHT COMMUNICATION 失效
公开(公告)号：JPS6416036A
公开(公告)日：1989-01-19
申请号：JP17157087
申请日：1987-07-09
申请人： FUJITSU LTD
发明人： CHIKAMA TERUMI , KIYONAGA TETSUYA , ONODA YOSHITO
IPC分类号： H04B10/572 , H04B10/07 , H04B10/2507 , H04B10/293 , H04B10/564
摘要： PURPOSE:To keep the detection output automatically to a constant level independently of the fluctuation of a receiving light level by controlling the intensity of the local oscillation light in response to the detection level of a detection signal. CONSTITUTION:The level of the detection signal 4 is detected in the coherent optical communication system where the received light 1 and the local oscillation light 2 are mixed and the result is made incident on the photodetector 3 to obtain a detection signal 4, to control the intensity of the local oscillation light 2 in response to the detected level. That is, in the heterodyne detection, since an intermediate frequency signal proportional to the product of the strength between the received light and the local oscillation light is obtained, the intensity of the local oscillation light is controlled so as to make the product constant, that is, the level of the detection signal is made constant. Thus, the detection output of a prescribed level is obtained without using the electric AGC (automatic gain control) circuit.

9. 发明专利

JPS62180322A OPTICAL ISOLATOR 失效
公开(公告)号：JPS62180322A
公开(公告)日：1987-08-07
申请号：JP2256486
申请日：1986-02-03
申请人： FUJITSU LTD
发明人： ONODA YOSHITO
IPC分类号： G02B27/28 , G02F1/09
摘要： PURPOSE:To obtain an optical isolator having a small size and a low cost by placing an emitting polarized light prism and an incident polarized light prism, so as to be opposed to each other on both sides of the reflecting surface of a Faraday rotor. CONSTITUTION:In both side end parts 8a, 8b of the reflecting surface of the Faraday rotor 8, the incident polarized light prism 7 and the emitting polarized light prism 9 are placed so as to be opposed to each other, and the incident surface f this incident polarized light prism and the emitting surface of the emitting polarized light prism 9 are inclined a little against the upper face of the Faraday rotor 8. Also, when a magnet 10 is attached to the side where the incident polarized light prism 7 and the emitting polarized light prism are placed, a magnetic field works on the direction as indicated with an arrow. With respect to the optical isolator of a constitution placed in this way, when an incident light 11 from, for instance, an optical fiber is made incident on the incident polarized light prism 7, this incident light is turned back by the Faraday rotor 8 and brought to a multiplex reflection, but it is brought to a total reflection by the lower face of the side where the Faraday rotor 8 turns, on the way of this multiplex reflection, and an emitting light 12 made incident on the emitting polarized light prism 9 and refracted consists of a structure to be transmitted to an optical fiber 14, for instance, through a lens, etc.

10. 发明专利

JPS62179777A OPTICAL SIGNAL DEMODULATION SYSTEM 失效
公开(公告)号：JPS62179777A
公开(公告)日：1987-08-06
申请号：JP2256186
申请日：1986-02-03
申请人： FUJITSU LTD
发明人： ONODA YOSHITO , GOTO MASAMI , CHIKAMA TERUMI
IPC分类号： G02B6/28 , G02B6/00 , H01L31/02 , H01L31/0232 , H01L31/10 , H04B10/00 , H04B10/516 , H04B10/61
摘要： PURPOSE:To simplify the structure and to reduce the cost of an optical signal demodulation system by providing a light transmission photoelectric sensor between a light emitting side optical fiber and a photodetecting side optical fiber to produce an electric signal corresponding to an optical signal from the sensor. CONSTITUTION:An optical signal 2 emitted from a light emitting side optical fiber 1 is formed by a lens 3 in a parallel beam. The beam is converted to an electric signal 5 by a potential difference proportional to the optical fiber generated by a light transmission photosensor 4 interposed between the lens 3 and a condensing lens 6. The signal 2 passed through the sensor 4 is incident through the lens 6 to a photodetecting side optical fiber 7 and transmitted to next stage. Thus, the sensor 4 is provided between the lens 3 and the lens 6 to simultaneously transmit the same contents at two or more positions and to simplify the structure.

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