The Furukawa Electric Co., Ltd.

Matsue Murata

Toshiya Hikami

Shoichi Negami

Shigeaki Nishikawa

Hiromi Ogawa

External modulator for optical communication

There is provided a method for modulating the polarization of light that allows detection of any modulated output regardless if the optical analyzers are rigidly held in place. According to a first aspect of the invention, a method for receiving light with a modulated polarization comprises steps of dividing the light being propagated through an optical fiber 1 with a polarization modulated in accordance with a modulation signal into three branched beams, causing one of the branched beams of light with a modulated polarization to pass through a .pi./2 phase corrector 2 and a first optical analyzer 3a and causing the remaining branched beams of light to respectively pass through second and third optical analyzers 3b and 3c without passing through any .pi./2 phase correctors before in order to receive light with a modualted intensity from the optical analyzers 3a, 3b and 3c. According to a second aspect of the invention, an apparatus for receiving light with a modulated plane is provided, said second optical analyzer 3b and said third optical analyzer 3c forming an angle of 49.degree. therebetween.

Method and apparatus for receiving light with a modulated polarization

There is provided an optical external modulator that can modulate the polarization of incident light without regulating the state of polarization of the light entering the modulator. Such a modulator can be suitably incorporated into an optical telecommunications system. An optical external modulator according to the invention comprises a substrate 1, an optical transmission line 7, a polarization modulating section 11 and a phase changing section 8 for changing the state of polarization of the light passing through the optical transmission line by applying stress to the optical transmission line 7 as a function of a modulation signal given to the modulator such that the phase difference between the X-component and the Y-component of the light being propagated through the optical transmission line 7 is shifted by (2m-1)*.pi./2 (m is a positive integer).

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Tokyo, Japan

Matsue Murata