Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1998-05-18
1999-10-26
Ben, Loha
Optical: systems and elements
Optical modulator
Light wave temporal modulation
359238, G02F 123
Patent
active
059738200
ABSTRACT:
A branch portion 107 branches a modulating signal into two signals in opposite phases. One of them is inputted to an FM laser element 102. The other one is adjusted in propagation delay and in amplitude and then is inputted to an IM suppressing laser element 110. The FM laser element 102 outputs an optical-frequency-modulated signal around a wavelength .lambda.1, whose optical intensity is also modulated. A local light source 104 outputs light at a wavelength .lambda.0, which is different from the oscillation wavelength .lambda.1 of the FM laser element 102 by .DELTA..lambda.. The IM suppressing laser element 110 outputs an optical-intensity-modulated signal. The three lights are combined and inputted to a photodetection portion 106. The photodetection portion 106 applies a heterodyne detection to inputted lights to output an FM modulated signal corresponding to a beat signal of the outputted optical signal from the FM laser element 102 and the outputted light from the local light source 104 at frequency corresponding to the difference .DELTA..lambda. between the original two wavelengths, and also cancels the average-value variation component in the FM modulated signal with an electrical signal produced by square-law detecting the optical-intensity-modulated signal from the IM suppressing laser element 110, thereby producing an ideal FM modulated signal.
REFERENCES:
patent: 4662715 (1987-05-01), Shutterly
patent: 4726644 (1988-02-01), Mathis
patent: 4824201 (1989-04-01), Kazovsky
K. Kikushima et al. "150-km Non-Repeated 60-channel AM-Video Transmission Employing Optical Heterodyne AM/FM Converter", ECOC '95, Th.L.3.1, Brussels, 1995, pp. 1047-1050.
Fuse Masaru
Kawashima Seiichiro
Kikushima Koji
Utsumi Kuniaki
Ben Loha
Matsushita Electric - Industrial Co., Ltd.
Nippon Telegraph and Telephone Corporation
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