Coherent optical receiver testing
AssigneeElenion Technologies, LLC
InventorsBernd-Harald Horst Jurgen Rohde, Erich Gottwald
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Abstract
An heterodyne apparatus and method for measuring performance parameters of a coherent optical receiver at RF frequencies is disclosed. Two coherent lights are launched into signal and LO ports of the receiver with an optical frequency offset f. One of the lights is modulated in amplitude at two phase-locked modulation frequencies F1 and F2. COR performance parameters are determined by comparing two frequency components of the COR output. The group delay variation (GDV) information is obtained by comparing phases of two time-domain traces corresponding to frequency components of the COR output signal at the two modulation frequencies shifted by the optical frequency offset f.
Claims7
A method for measuring a characteristic of an optical circuit having an input optical port and an output port, the method comprising:
- a) feeding test light into an input port of an optical modulator having a non-linear electro-optical modulation transfer characteristic;
- b) applying an electrical modulating signal having a substantially sinusoidal waveform of a modulation frequency F1 to the optical modulator, the electrical modulating signal having an amplitude that is sufficient to modulate an optical power of the test light at the first modulation frequency F1 and a second harmonic thereof F2=2F1;
- c) recording a duration of an output signal from the output port of the optical circuit;
- and,
- d) processing the duration of the output signal to obtain therefrom a first signal corresponding to a frequency component of the output signal at or near the modulation frequency F1 and a second signal corresponding to a frequency component of the output signal at or near the second harmonic frequency F2;
- and,
- e) comparing the first signal to the second signal to determine the characteristic of the optical circuit.
An apparatus for measuring a frequency characteristic of an optical circuit having an input optical port and an output port, the apparatus comprising:
- an optical source to generate test light;
- an optical modulator disposed to receive the test light and to output modulated light, the optical modulator having a non-linear electro-optical modulation transfer characteristic;
- an electrical signal generator coupled to the optical modulator and configured to generate an electrical modulating signal having a substantially sinusoidal waveform at a modulation frequency F1 and an amplitude that is sufficient to modulate an optical power of the test light at the first modulation frequency F1 and a second harmonic thereof F2=2F1 when the modulating signal is provided to the optical modulator;
- a signal recorder coupled to the output port of the optical circuit to receive an output signal therefrom and configured to record a duration thereof;
- and,
- a controller coupled to the signal recorder and configured to obtain, from the duration of the output signal, a first signal corresponding to a frequency component of the output signal at or near the modulation frequency F and a second signal corresponding to a frequency component of the output signal at or near a second modulation frequency 2F.
Dependencies are inferred from the claim text.