Optical hybrid with 3.times.3 coupling device
AssigneeKoninklijke PTT Nederland N.V.
InventorsMattijs O. van Deventer, Johannes J. G. M. van Der Tol
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Abstract
In known coherent optical receivers comprising two detectors, optical 90.degree. hybrids have a `throughput` .ltoreq.25%. Theoretical analysis reveals that a higher `throughput` of up to a maximum of approximately 29.3% is possible. The invention provides such a 90.degree. hybrid (30) of the coupler type with the aid of a 2.times.2 port which is based on a loss-free 3.times.3 directional coupler having the maximum throughput ratios between two of the inputs (31/39, 32/40) and two of the outputs (39/34, 40/35) and the 90.degree. phase difference between said two outputs, the third input and the third output not being used. An integrated version employing indium phosphide is described.
Claims13
Optical hybrid having a first and a second input port, respectively, for launching a first and a second light signal, and having a first and a second output port, respectively, for coupling out a first and a second output signal, the output signals including, respectively, a first and a second coherent product of each of the input signals, with a mutual phase difference of approximately 90.degree., characterized in that the hybrid comprises a 3.times.3 coupling device of three coupling waveguides having three inputs and three outputs, two of the inputs forming the input ports, and two of the outputs forming the output ports, the power throughput of each of the input ports to each of the output ports being greater than 25%.
Coherent optical receiver comprising an optical local oscillator, an optical hybrid having two input ports for launching matched signals and a number n.gtoreq.2 of output ports for coupling out coherent products, differing in phase, of the two launched signals, and detection means for detecting the coherent products and delivering two output signals differing mutually in phase by 90.degree., characterized in that the detection means comprise only two photodetectors, each coupled to one of the output ports of the optical hybrid, and in that the power throughput of each of the input ports of the optical hybrid to each of the output ports coupled to the photodetectors is greater than 25%.
Coherent optical receiver comprising an optical local oscillator, an optical hybrid having two input ports for launching matched signals and a number n.gtoreq.2 of output ports for coupling out coherent products, differing in phase, of the two launched signals, and detection means for detecting the coherent products and delivering two output signals differing mutually in phase by 90.degree., characterized in that
- said optical hybrid comprises a 3.times.3 coupling device of three coupling waveguides having three inputs and three outputs, two of the inputs forming the input ports, and two of the outputs forming two of the output ports, the power throughput of each of the input ports to each of the output ports being greater than 25%, and in that
- the detection means comprise only two photodetectors, each coupled to one of the output ports of the optical hybrid.
Dependencies are inferred from the claim text.