초록 ▼

Device for optical heterodyne detection of an optical signal beam and an optical transmission system provided with such a device. An optical heterodyne detection device is described in which with the aid of three controllable elements (A, B and C), to influence the state of polarization and having a

Device for optical heterodyne detection of an optical signal beam and an optical transmission system provided with such a device. An optical heterodyne detection device is described in which with the aid of three controllable elements (A, B and C), to influence the state of polarization and having a limited control range, such as Faraday rotators or birefringent electro-optical crystals, the state of polarization of radiation originating from a local oscillator (30) is made to correspond to the signal beam transmitted through a long-distance transmission fibre (10).

대표청구항 ▼

A device for optical heterodyne detection of an input signal in the form of an optical beam of radiation having a varying state of polarization, such device comprising: a. a local oscillator for generating a polarized beam of radiation having a state of polarization; b. means for combining said loca

A device for optical heterodyne detection of an input signal in the form of an optical beam of radiation having a varying state of polarization, such device comprising: a. a local oscillator for generating a polarized beam of radiation having a state of polarization; b. means for combining said local oscillator radiation with said input signal radiation to form a beam of combined radiation which includes said input signal radiation; c. an electro-optical converter for converting said beam of combined radiation into an electrical signal, so that the device achieves non-diversity detection of said input signal; d. a plurality of not more than three controllable polarization influencing elements respectively coupled to the local oscillator radiation and/or the input signal radiation to influence the polarization state of such radiation, each such element having a limited control range of such polarization influencing effect, the control range limitations being such that none of said elements can influence the polarization state of the input signal radiation over any endless variation of such polarization state in any direction; and e. means for deriving from said electrical signal a plurality of control signals for controlling said polarization influencing elements so that any one of said elements is gradually readjustable within its control range, during which readjustment the polarization influence of said one element changes and the others of said elements provide a degree of polarization influence which continuously compensates for the changing polarization influence of said one element; whereby the polarization state of said input signal radiation included in said combined beam is continuously controlled relative to the polarization state of said local oscillator radiation despite the limited control ranges of said polarization influencing elements.