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1. 发明专利

JPH02110524A HETERODYNE DETECTION RECEIVER FOR COHERENT OPTICAL COMMUNICATION 失效
公开(公告)号：JPH02110524A
公开(公告)日：1990-04-23
申请号：JP26294388
申请日：1988-10-20
申请人： FUJITSU LTD
发明人： NAITO TAKAO , CHIKAMA TERUMI , WATANABE SHIGEKI , SHIMIZU TETSUYA , ONODA YOSHITO
IPC分类号： G02F2/00 , H04B10/07 , H04B10/516 , H04B10/61
摘要： PURPOSE:To easily constitute an optical system and to attain the reception of high sensitivity by providing at least two light receiving devices and monitoring a polarizing condition in an electric signal step. CONSTITUTION:A signal light is given through a polarization operating device 20 to a mixing circuit 21 and a local oscillating light is outputted from an optical local oscillating circuit 22 and given to the mixing circuit 21. Here, the signal light and local oscillating light are multiplexed. After that, the multiplexed light is separated to two orthogonal polarizing components by using a polarization separating device 23 and heterodyne detection is executed respectively by light receiving devices 24 and 25. Then, an intermediate frequency signal is obtained. The intermediate frequency signal outputted from the light receiving devices 24 and 25 is given to a 90 deg. hybrid coupler 26 and an output signal from an output port P4 is demodulated up to a demodulator 27 and outputted. A polarization control circuit 29 outputs control signals A and B based on signals (a) and (b) and drives the polarization operating device 20 and the polarizing condition of the signal light is suitably controlled. Thus, the optical system can be easily constituted to monitor the polarizing condition and the reception of high sensitivity can be executed.

2. 发明专利

JPH02140006A DC COUPLING TYPE PHOTODETECTOR 失效
公开(公告)号：JPH02140006A
公开(公告)日：1990-05-29
申请号：JP29107288
申请日：1988-11-19
申请人： FUJITSU LTD
发明人： SHIMIZU TETSUYA , CHIKAMA TERUMI , WATANABE SHIGEKI , ONODA YOSHITO , NAITO TAKAO
IPC分类号： H04B10/60 , H03F3/58 , H03F3/60 , H04B10/40 , H04B10/50 , H04B10/54 , H04B10/61
摘要： PURPOSE:To improve the standing wave ratio by coupling a signal output terminal of a photodetector to an input terminal of a distribution type or travelling wave type amplifier in terms of DC. CONSTITUTION:A bias resistor R8 is added to a photodetector 11, a resistor Rd is connected to a gate of a FET 13 and a resistor Rg is connected to the drain to take matching with the input side filter. Thus, an inductance 14 and a capacitive susceptance of the FET 13 constitute a constant K type filter even in the input and output side and the filters are connected in multi-state. Thus, the broad band characteristic of the photodetector is realized.

3. 发明专利

JPS6461735A ARRANGEMENT STRUCTURE OF PROGRESSIVE WAVE TYPE OPTICAL AMPLIFIER 失效
公开(公告)号：JPS6461735A
公开(公告)日：1989-03-08
申请号：JP21891687
申请日：1987-09-01
申请人： FUJITSU LTD
发明人： ONODA YOSHITO , CHIKAMA TERUMI , SHIMIZU TETSUYA , NAITO TAKAO
IPC分类号： H01S3/10 , G02F1/35 , H04B10/293 , H04B10/40 , H04B10/50 , H04B10/60
摘要： PURPOSE:To obtain a constant gain irrelevantly to the plane of polarization of light to be amplified by cascading progressive wave type optical amplifiers on the optical axis of the light to be amplified and amplifying TE- and TM- mode polarized wave components individually. CONSTITUTION:A progressive wave type optical amplifier 2 with an active layer 4 and a progressive wave type optical amplifier 6 with an active layer 8 are arranged on the optical axis OA in right-angle relation. Incident light is amplified by the amplifier 2 and projected having amplitudes GAcostheta and alphaGAsintheta. Then the TE-mode polarized component of the projection light of the amplifier 2 is amplified as the TM-mode polarized component by the amplifier 6 and the (y)-directional amplitude of its projection light is alphaG Acostheta. Further, the TM-mode polarized wave component of the projection light of the amplifier 2 is amplified as the TE-mode polarized wave component by the amplifier 6 and the (x)-directional component of the projection light is alphaG Asintheta. The gains of the (x)- and (y)-directional components are equal to alphaG and do not depend upon theta.

4. 发明专利

JPH0352341A RECEIVER FOR COHERENT OPTICAL COMMUNICATION 失效
公开(公告)号：JPH0352341A
公开(公告)日：1991-03-06
申请号：JP18590689
申请日：1989-07-20
申请人： FUJITSU LTD
发明人： NAITO TAKAO , CHIKAMA TERUMI , WATANABE SHIGEKI , SHIMIZU TETSUYA , ONODA YOSHITO
IPC分类号： H04B10/516 , H04B10/07 , H04B10/2513 , H04B10/61
摘要： PURPOSE:To improve the transmission speed by multiplying respectively a signal from an oscillation circuit and a signal from a photodetector, outputting the product from an electric 90 deg. hybrid circuit, retarding the signal in response to the frequency to compensate electric dispersion. CONSTITUTION:When a received signal light is inputted to an optical 90 deg. hybrid circuit 4, the signal light is bisected and synthesized with a local light having the phase difference of 90 deg. respectively and the synthesized light is led respectively to photodetectors 6, 8. After a signal from the photodetectors 6, 8 and a signal from an oscillation circuit 10 oscillated at a prescribed frequency are multiplied with mixers 12, 14, the result is outputted via an electric 90 deg. hybrid circuit 16. Thus, a signal in nearly a //base band is up-converted into an intermediate frequency band again, the dispersion of an optical fiber is compensated and then compensated again to obtain a base band signal. Thus, the transmission speed is improved.

5. 发明专利

JPH02933A OPTICAL AMPLIFIER 失效
公开(公告)号：JPH02933A
公开(公告)日：1990-01-05
申请号：JP4979689
申请日：1989-03-03
申请人： FUJITSU LTD
发明人： ONODA YOSHITO , CHIKAMA TERUMI , SHIMIZU TETSUYA , NAITO TAKAO
IPC分类号： G02F1/35
摘要： PURPOSE:To increase the gain of the optical amplifier constituted by using a single progressive wave type optical amplifier by propagating light reciprocally in the progressive wave type optical modulator and amplifying the light twice. CONSTITUTION:Light which passes through a polarized light separating means 1, the progressive wave type optical amplifier 2, and a polarization plane rotating means 3 in this order is reflected by a reflecting mirror 4 and light which passes through a polarization plane rotating means 3 and the progressive wave type optical amplifier 2 in this order is outputted through the polarized wave separating means 1 through an optical path different from the incident light. The light, therefore, travels in the progressive wave type optical amplifier 2 reciprocally, so the light is amplified twice and the gain is increased. Consequently, the gain of the optical amplifier constituted by using the single progressive wave type optical amplifier can be increased.

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