Coherent Optical Receiver Performance Measurement Apparatus
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Solution Overview
Problem
Current methods are inadequate for accurately measuring the performance indices, such as bandwidth and common mode rejection ratio, of coherent optical receivers, especially when a 90-degree optical hybrid is connected, as they are designed for balanced optical receivers and not coherent optical receivers.
Innovation Solution
An apparatus comprising a beam splitter, optical modulators, polarization controllers, a variable optical delay line, and a network analyzer is used to generate and control optical signals with specific phase and intensity conditions, allowing for direct measurement of bandwidth and common mode rejection ratio of coherent optical receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods for balanced optical receivers are used on coherent optical receivers, then the measurement process becomes complicated and inaccurate, but the existing methods are simpler to implement for balanced receivers
Solution Approach 1:
The patent introduces a 90-degree optical hybrid as an intermediary component that transforms the measurement problem. By converting the coherent optical receiver measurement into equivalent balanced receiver measurements through the optical hybrid, the system achieves accurate measurement of coherent receivers using modified balanced receiver measurement techniques, thus resolving the contradiction between measurement accuracy and device complexity
Solution Approach 2:
The patent changes the measurement parameters by introducing specific test signals with controlled phase relationships (0-degree and 90-degree phase shifts) and using the optical hybrid to manipulate these parameters. This allows the measurement system to extract coherent receiver performance metrics through parameter transformation rather than direct measurement, improving accuracy without proportionally increasing complexity
2Ease of operation
If direct measurement of common mode rejection ratio is attempted using phase modulation and maximum value assumptions, then the measurement can be performed, but the measurement accuracy is limited
Solution Approach 1:
The patent implements a feedback mechanism where the measurement system iteratively adjusts the test signals and measures the output to calculate the common mode rejection ratio. By using the measured results to refine subsequent measurements and applying mathematical processing to eliminate assumptions about maximum values, the system achieves both ease of operation and high measurement precision
Solution Approach 2:
The patent performs preliminary calibration and signal setup actions before the actual measurement. The optical hybrid and test signal generators are pre-configured with specific phase relationships, and the system performs initial characterization to establish baseline measurements. This preliminary action eliminates the need for assumptions during the actual measurement process, improving accuracy while maintaining operational simplicity
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 accurate measurement of bandwidth and common mode rejection ratio, improving the assessment of coherent optical receiver performance beyond what is possible with traditional methods.
Implementation Method 1
a beam splitter for dividing a light signal from a light source into two paths having equal intensity
Implementation Method 2
a first optical modulator for modulating an optical signal in the first path with a first control signal and a second optical modulator for modulating an optical signal in the second path with a second control signal
Implementation Method 3
a first polarization controller for controlling a polarization state of a modulated optical signal in the first path and a second polarization controller for controlling a polarization state of a modulated optical signal in the second path
Implementation Method 4
a variable optical delay line for controlling a time delay of a modulated optical signal in the second path
Implementation Method 5
a coherent optical receiver for receiving the modulated optical signals from the first and second paths
Data Source
AI summary
An apparatus for measuring performance of a coherent optical receiver includes a beam splitter splitting light into first and second paths, a first optical modulator modulating the first path light, a variable optical attenuator controlling an optical power of the first optical modulator, a first polarization controller transmitting a signal controlling polarization of an output of the variable optical attenuator to the coherent optical receiver, a second optical modulator modulating the second path light, a variable optical delay line delaying time of an output of the second optical modulator, a second polarization controller transmitting a signal controlling polarization of an output of the variable optical delay line to the coherent optical receiver, a network analyzer measuring performance of the coherent optical receiver and controlling the optical modulators, and a controller transmitting a control signal to the optical modulators.