Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1993-05-13
1995-12-05
Boudreau, Leo H.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359189, H04B 1006
Patent
active
054734630
ABSTRACT:
In known coherent optical receivers with two detectors, optical 90.degree. hydrids have a throughput .ltoreq.25%. Theoretical analysis shows that a higher throughput, up to a maximum of approximately 29.3%, is possible. The invention provides such a 90.degree. hybrid (30) of the polarisation type. In an optical hybrid (3) having a structure known per se, i.e. polarisation controllers (38, 39) at the inputs (40 and 41) of a power coupler (42), and polarisers (45, 46) at the outputs (43 and 44) thereof, the polarisation controllers and the polarisers are put into such positions, that the points on the Poincare sphere, which correspond to those positions, comply with two conditions which guarantee a 90.degree. phase difference and the higher throughput. For example, the positions correspond to points which represent positions in which the polarisation controllers produce mutually opposite elliptical polarisations at an angle .alpha. and the polarisers are placed linearly at angles .alpha. and -.alpha., and .alpha.=32.8.degree..
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Boudreau Leo H.
Koninklijke PTT Nederland N.V.
Mehta Bhavesh
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