Matsushita Electric Industrial Co., Ltd.

Nippon Telegraph and Telephone Corporation

Seiichiro Kawashima

Masaru Fuse

Jun Ohya

Kuniaki Utsumi

Koji Kikushima

The signal converter of the present invention receives a multichannel video signal and converts the video signal into a microwave signal, the phase of which has been modulated with the video signal. The signal converter includes: a laser light source; a modulating section for modulating the phase of output light of the laser light source with the multichannel video signal and modulating the intensity of the output light with the microwave signal; and a light receiver for receiving the output light modulated by the modulating section and for outputting the microwave signal, the phase of which has been modulated with the multichannel video signal.

Signal converter, optical transmitter and optical fiber transmission system

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.

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Kanagawa, Japan

Seiichiro Kawashima