Optical Delay Phase-Noise Measurement with Laser Wavelength Tuning
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Solution Overview
Problem
Existing methods for measuring phase noise in high-frequency signals using optical delay branches have a lower limit of applicability above 10 GHz, and stabilizing phase shift in optical fibers is challenging due to environmental influences.
Innovation Solution
Adjusting the laser wavelength to change the phase shift in optical fibers, rather than relying on mechanical adjustments of optical fiber length or chromatic dispersion, to achieve the desired quadrature condition in the mixer, using a feedback loop to maintain the DC component at zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical adjustments of optical fiber length or chromatic dispersion are used to achieve quadrature condition, then phase shift can be adjusted, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical adjustment mechanisms (optical fiber length adjustment, chromatic dispersion adjustment) with electrical control of laser wavelength. By varying the laser wavelength through temperature or current control, the phase shift is adjusted electrically without any mechanical moving parts, thereby simplifying the device structure and reducing complexity.
Solution Approach 2:
The patent changes the operating parameter of the laser (wavelength) to achieve phase adjustment. By controlling the laser wavelength through temperature or supply current, the phase shift in the optical fiber is varied, providing a simple and effective method to achieve quadrature condition without mechanical adjustments.
2Ease of operation
If optical fiber length is changed to adjust phase shift, then quadrature condition can be achieved, but environmental stability deteriorates
Solution Approach 1:
Instead of changing the physical length of the optical fiber (which is sensitive to environmental factors), the patent changes the laser wavelength parameter to achieve phase adjustment. This approach maintains the optical fiber length constant, thereby improving environmental stability while still allowing phase tuning through wavelength control.
Solution Approach 2:
The patent replaces mechanical/physical adjustments (fiber length change) with electrical/optical control (laser wavelength modulation). This substitution eliminates the need to physically alter the optical fiber, which would be susceptible to environmental influences, and instead uses controlled wavelength variation that is more stable and reversible.
3Manufacturing precision
If expensive mechanical adjustment components are used, then precise phase control is achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive mechanical adjustment components with a cost-effective electrical control system for the laser. By using temperature or current control circuits to adjust the laser wavelength, precise phase control is achieved without the need for costly mechanical actuators, positioners, or variable optical attenuators.
Solution Approach 2:
The patent achieves precise phase control by varying the laser operating parameters (temperature, current, wavelength) rather than using expensive mechanical components. This parameter-based control approach is both precise and cost-effective, as it utilizes standard electronic control circuits instead of specialized mechanical adjustment mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables phase noise measurement down to the MHz range with lower costs and simpler control circuits, overcoming environmental instability issues and extending the measurement range without the need for expensive mechanical adjustments.
Implementation Method 1
setting the phase in the optical branch by means of setting the wavelength of the laser, which, through the chromatic dispersion in at least one optical fibre, preferably in two optical fibres, causes the desired phase shift
Implementation Method 2
the laser wavelength increases very linearly with increasing temperature
Data Source
Figure 1
AI summary
The present invention relates to a method of measuring phase noise on a mixer or phase detector in a device for measuring the phase noise of a high-frequency signal by means of at least one optical delay unit. Provided are a first delay branch (I), comprising a first optical fibre (8'), which comprises a length (L') with a chromatic dispersion (D') and refraction index (n'), and a second delay branch (II), comprising a second optical fibre (8"), which comprises a length (L") with a chromatic dispersion (D") and refraction index (n").