Optical Coherent Transponder Skew Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring in-phase/quadrature skew in optical coherent transponders are not accurate for complex modulation formats and require expensive equipment, such as Optical Modulation Analyzers.
Innovation Solution
A method and system using an Optical Spectrum Analyzer to measure optical power for harmonics of optical signals, comparing the measurements to a mapping of optical power to known skew values, and determining the skew, which can be more sensitive on either the higher or lower frequency side of the spectrum, allowing for more accurate and cost-effective skew measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive Optical Modulation Analyzers are used for skew measurement, then measurement equipment capability is improved, but cost increases significantly
Solution Approach 1:
The patent replaces expensive Optical Modulation Analyzers with a low-cost Optical Spectrum Analyzer combined with a simple processing system. The OSA is a standard, widely available instrument that is much cheaper than specialized OMA equipment, while the processing logic uses basic mathematical operations on spectral measurements to derive skew values with sufficient accuracy for practical applications.
Solution Approach 2:
The patent substitutes complex specialized measurement hardware with a simpler optical measurement system followed by computational processing. Instead of using dedicated skew measurement circuits or complex modulation analysis hardware, the system uses standard optical spectrum analysis combined with mathematical processing of the spectral data to determine skew, replacing specialized mechanical/electrical measurement systems with an optical-computational hybrid approach.
2Ease of operation
If existing skew measurement techniques are used, then measurement capability is provided, but accuracy for complex modulation formats deteriorates
Solution Approach 1:
The patent changes the measurement parameter from time-domain or phase-domain analysis to frequency-domain power ratio analysis. By measuring the ratio of optical powers at different frequency offsets from the carrier and using the relationship between these power ratios and skew values, the system achieves accurate skew measurement for complex modulation formats. The method involves measuring optical power at the carrier frequency and at offset frequencies, then calculating skew from the power ratio using established relationships.
Data Source
AI summary
Systems and methods for measuring the in-phase/quadrature (I/Q) skew of optical signals. The method may be used to characterize the I/Q skew of optical signals transmitted by optical coherent transponders in complex modulation formats. The method may include providing an input signal to a transponder to produce a periodic (and generally sinusoidal) output signal, providing the output signal to a test system including an optical spectrum analyzer, measuring the optical power of a first harmonic of the signal, and comparing the measured optical power to calibration data to determine the I/Q skew. The optical power may be analyzed in a portion of the spectrum where sensitivity of the power to changes in skew is highest. The calibration data may map previously-obtained optical power measurements to corresponding known skew amounts. The system may provide more accurate skew measurements using less expensive equipment than existing skew measurement methods.