Photonic-based cross-correlation homodyne detection with low phase noise

• US 8,155,913 B2
• Filed: 11/13/2008
• Issued: 04/10/2012
• Est. Priority Date: 11/13/2007
• Status: Active Grant

• Current Assignee: Oewaves Incorporated
• Original Assignee: Oewaves Incorporated
• Inventors: Eliyahu, Danny, Morozov, Nikolai, Maleki, Lute
• Primary Examiner(s): Lau, Tung S
• Application Number:
  US12/270,845
• Publication Number:
  US 20090208205A1
• Time in Patent Office: 1,244 Days
• Field of Search: 702/117
• US Class Current: 702/117
• CPC Class Codes: G01R 31/2824 testing of oscillators or resonators
• CPC Class Codes: H04B 10/61 Coherent receivers
• CPC Class Codes: H04B 10/63 Homodyne , i.e. coherent receivers where the local oscillator is locked in frequency and phase to the carrier signal

Abstract

In one aspect, this document provides an implementation of a system for characterizing an oscillator. This system includes an input port that receives an oscillation signal from an oscillator under test; an input port signal splitter that splits the received oscillation signal into a first oscillation signal and a second oscillation signal; a first photonic signal processing branch circuit that processes the first oscillation signal to produce a first branch output signal; a second photonic signal processing branch circuit that processes the second oscillation signal to produce a second branch output signal; a dual channel signal analyzer that receives the first and second branch output signals to measure noise in the received oscillation signal; and a computer controller that controls the first and second photonic signal processing branch circuits and the dual channel signal analyzer to control measurements of the noise in the received oscillation signal.

Claims

1. A system for characterizing an oscillator, comprising:

an input port that receives an electrical oscillation signal from an oscillator under test;

an input port signal splitter that splits the received electrical oscillation signal into a first electrical oscillation signal and a second electrical oscillation signal;

a first photonic signal processing branch circuit that coverts the first electrical oscillation signal into a first optical signal carrying the first electrical oscillation signal and processes the first optical signal to produce a first electrical branch output signal;

a second photonic signal processing branch circuit that coverts the second electrical oscillation signal into a second optical signal carrying the second electrical oscillation signal and processes the second optical signal to produce a second electrical branch output signal;

a dual channel signal analyzer that receives the first and second electrical branch output signals to measure noise in the received electrical oscillation signal; and

a computer controller that controls the first and second photonic signal processing branch circuits and the dual channel signal analyzer to control measurements of the noise in the received electrical oscillation signal.

2. The system as in claim 1, wherein:

the first photonic signal processing branch circuit comprises;

a first signal splitter to splits the first oscillation signal into a first branch signal and a second branch signal;

a photonic branch that receives the first branch signal and comprises a laser that produces a laser beam, an optical modulator that modulates the laser beam in response to the first branch signal to produce a modulated laser beam that carries the first branch signal, an optical delay unit that transmits the modulated laser beam to produce a delay in the modulated laser beam, and an optical detector that converts the modulated laser beam into a detector signal;

an electrical branch that receives the second branch signal and comprises a voltage controlled phase shifter that receives the second branch signal and to changes a phase of the second branch signal to produce an output signal; and

a signal mixer that mixes the detector signal and the output signal to produce the first branch output signal.

3. The system as in claim 2, wherein:

the optical delay unit comprises a fiber delay line.

4. The system as in claim 2, wherein:

the voltage controlled phase shifter is under a control of the computer controller.

5. The system as in claim 4, wherein:

the computer controller controls the voltage controlled phase shifter to set a phase of the signal mixer at a quadrature condition.

6. A system for characterizing an oscillator, comprising:

an input port that receives an oscillation signal from an oscillator under test;

an input port signal splitter that splits the received oscillation signal into a first oscillation signal and a second oscillation signal;

a signal splitter to splits the first oscillation signal into a first branch signal and a second branch signal;

a first branch circuit that is coupled to the signal splitter to receive the first branch signal and includes a first branch splitter that splits the first branch signal into a first signal and a second signal, a first photonic branch circuit that receives the first signal, a first electrical branch that receives the second signal, and a first signal combiner that combines outputs from the first photonic branch and the first electrical branch to produce a first branch circuit signal,

wherein the first photonic branch circuit includes a first laser that produces a laser beam, a first optical modulator that modulates the laser beam in response to the first signal to produce a modulated laser beam that carries the first signal, a first optical delay unit that transmits the modulated laser beam to produce a delay in the modulated laser beam, and a first optical detector that converts the modulated laser beam into a first detector signal to the first signal combiner, and wherein the first electrical branch receives the second signal and comprises a voltage controlled phase shifter that receives the second signal and to change a phase of the second signal to produce an output signal to the first signal combiner;

a second branch circuit that is coupled to the signal splitter to receive the second branch signal and includes a second branch splitter that splits the second branch signal into a third signal and a fourth signal, a second photonic branch circuit that receives the third signal, a second electrical branch that receives the fourth signal, and a second signal combiner that combines outputs from the second photonic branch and the second electrical branch to produce a second branch circuit signal,

wherein the second photonic branch circuit includes a second laser that produces a laser beam, a second optical modulator that modulates the laser beam in response to the third signal to produce a modulated laser beam that carries the third signal, a second optical delay unit that transmits the modulated laser beam to produce a delay in the modulated laser beam, and a second optical detector that converts the modulated laser beam into a second detector signal to the second signal combiner, and wherein the second electrical branch receives the fourth signal and includes a voltage controlled phase shifter that receives the fourth signal and to change a phase of the fourth signal to produce an output signal to the second signal combiner;

a dual channel signal analyzer that receives the first and second branch circuit signals to measure noise in the received oscillation signal; and

a controller that controls the first and second photonic branch circuits and the dual channel signal analyzer to control measurements of the noise in the received oscillation signal.

7. The system as in claim 6, wherein:

the first or second optical delay unit includes a fiber delay line.

8. The system as in claim 6, wherein:

the voltage controlled phase shifter in the first or second electrical branch is under a control of the controller.

9. The system as in claim 8, wherein:

the controller controls the voltage controlled phase shifter to set a phase of the first or second signal combiner at a quadrature condition.