Coherent optical receiver testing
AssigneeElenion Technologies, LLC
InventorsBernd-Harald Horst Jurgen Rohde, Erich Gottwald
Life of this patent
Estimating the term…
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.
Claims20
A method for measuring a group delay variation (GDV) for a coherent optical receiver (COR) comprising first and second optical signal (OS) ports, a local oscillator (LO) port, and one or more output ports, the method comprising:
- a) providing first light into the first OS port and the LO port of the COR, wherein the first light is modulated in amplitude at a first modulation frequency F1 and a second modulation frequency F2>F1 in a phase locked manner;
- b) providing second light that is coherent with the first light and is shifted in optical frequency from the first light by a frequency shift f<F1 into the second OS port and the LO port of the COR;
- c) obtaining, from an output COR signal received from the one or more output ports of the COR, a first time-domain trace corresponding to a frequency component of the output signal at a first shifted modulation frequency (F1+f) or (F1−f), and a second time-domain trace corresponding to a frequency component of the output signal at a second shifted modulation frequency (F2+f) or (F2−f);
- d) determining a phase shift between the first and second time-domain traces;
- and
- e) computing the GDV based on the phase shift.
An apparatus for measuring a group delay variation (GDV) for a coherent optical receiver (COR), the COR comprising an optical signal (OS) port, a local oscillator (LO) port, and one or more output ports, the apparatus comprising:
- one or more coherent light sources configured to provide first and second lights with an optical frequency shift f therebetween;
- first and second output optical ports for coupling one of the first and second lights into a local oscillator (LO) input port of the COR and the other of the first and second lights into an optical signal port of the COR;
- an optical modulator disposed to modulate the first light simultaneously at a first modulation frequency F1>f and a second modulation frequency F2>F1 in a phase-locked manner;
- an electrical signal recorder configured to receive a first output COR signal from the one or more output ports of the COR and to record a duration thereof;
- and
- a controller coupled to the electrical signal recorder and configured to obtain, from the duration of the first output COR signal, a first time-domain trace corresponding to a frequency component of the first output COR signal at a first shifted modulation frequency (F1+f) or (F1−f) and a second time-domain trace corresponding to a frequency component of the first output COR signal at a second shifted modulation frequency (F2+f) or (F2−f), to determine a phase shift between the first and second time-domain trances, and to compute the GDV based on the phase shift.
A method for measuring a GDV of a coherent optical receiver (COR), the COR comprising an optical signal (OS) port, a local oscillator (LO) port, and one or more output ports, the method comprising:
- splitting light from a coherent light source into first and second lights;
- frequency shifting one of the first or second lights by a frequency shift f,
- modulating the first light in amplitude at a first modulation frequency F1 that is greater than f and a second modulation frequency F2 in a phase-locked manner, wherein F2>F1>f,
- providing one of the first and second lights into a signal port of the COR, and the other of the first and second lights into a local oscillator (LO) port of the COR;
- obtaining, from an output COR signal received from the one or more output ports of the COR, a first time-domain trace corresponding to a frequency component of the output signal at a first shifted modulation frequency (F1+f) or (F1−f), and a second time-domain trace corresponding to a frequency component of the output signal at a second shifted modulation frequency (F2+f) or (F2−f);
- determining a phase shift between the first and second time-domain traces;
- and
- computing the GDV based on the phase shift.
Dependencies are inferred from the claim text.