Communication by radio waves and optical waveguides
First Claim
1. A transducer for converting a radio signal, via an electrical signal, to an optical signal in a waveguide and vice versa comprising an electroabsorption modulator optically coupled to said waveguide, at least one antenna electrically coupled to said electroabsorption modulator, and an electrical constant-current source coupled to said electroabsorption modulator to bias it.
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Accused Products
Abstract
The invention relates to improvements to full-duplex bi-directional opto-electrical transducers, primarily for use in radio-over-fiber installations, such as remote-antenna installations for cellular radio apparatus. The transducer is of the kind based on an electroabsorption modulator, and the first improvement consists in biasing it by means of a constant-current source rather than conventionally by directly setting a bias voltage. With appropriate selection of the EAM, a preset constant current source is considered adequate, but its setting may be adjusted to operating conditions by a control algorithm if found desirable. A second improvement consists in increasing the effective load impedance of the EAM by using an inductive load that forms a tuned circuit with the internal capacitance of the EAM, resonant at a frequency in the operating range..
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Citations
21 Claims
- 1. A transducer for converting a radio signal, via an electrical signal, to an optical signal in a waveguide and vice versa comprising an electroabsorption modulator optically coupled to said waveguide, at least one antenna electrically coupled to said electroabsorption modulator, and an electrical constant-current source coupled to said electroabsorption modulator to bias it.
- 3. A transducer for converting radio signals, via electrical signals, to optical signals in waveguides and vice versa comprising an electroabsorption modulator having an internal capacitance optically coupled to said waveguide, at least one antenna electrically coupled to said electroabsorption modulator and a load impedance connected to said electroabsorption modulator wherein said load impedance is inductive and forms with said internal capacitance a parallel tuned circuit.
- 11. A method of converting radio signals, via electrical signals, to optical signals in waveguides and vice versa comprising coupling an electroabsorption modulator optically to said waveguide, coupling at least one antenna electrically to said electroabsorption modulator, and biasing said electroabsorption modulator by means of an electrical constant-current source.
- 15. A method of converting radio signals, via electrical signals, to optical signals in waveguides and vice versa comprising optically coupling to said waveguide an electroabsorption modulator having an internal capacitance, electrically coupling at least one antenna to said electroabsorption modulator and connecting an inductive load impedance to said electroabsorption modulator to form with said internal capacitance a parallel tuned circuit.
Specification