Tunable Optical Filter OSNR Measurement
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Solution Overview
Problem
In optical communication systems, the superposition of secondary signals onto main signal light for monitoring purposes can lead to fluctuations, which deteriorate the accuracy of optical signal-to-noise ratio (OSNR) measurement.
Innovation Solution
An optical communication system is designed with an optical transmitter and receiver that include a drive signal generator, optical modulator, tunable optical filter, photodetector, filter controller, superimposed signal detector, and OSNR calculator. The system uses a predetermined superposition pattern with superimposed and non-superimposed periods to control the center transmittance frequency of the tunable optical filter, allowing for accurate detection of secondary signals and OSNR calculation during specific periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second signal is superimposed to the first signal for monitoring purposes, then the functionality of the optical communication system is improved, but the measurement accuracy of optical signal-to-noise ratio is deteriorated
Solution Approach 1:
The patent applies periodic action by dividing the signal transmission into alternating superimposed periods and non-superimposed periods. During non-superimposed periods, the second signal is not superimposed, allowing for accurate OSNR measurement. During superimposed periods, the second signal is present for monitoring purposes. This periodic switching resolves the contradiction by separating the two functions in time.
Solution Approach 2:
The patent segments the signal transmission into distinct time intervals: superimposed periods where the second signal is present for monitoring, and non-superimposed periods where only the first signal is transmitted for accurate OSNR measurement. This temporal segmentation allows both monitoring functionality and measurement accuracy to be achieved in different segments of the overall transmission.
2Reliability
If continuous monitoring of the second signal is performed, then the reliability of detection is improved, but the complexity of timing synchronization increases
Solution Approach 1:
The patent uses periodic action by establishing a predetermined superposition pattern with regular superimposed and non-superimposed periods. The optical receiver is configured to detect the second signal during superimposed periods and measure OSNR during non-superimposed periods according to this predetermined pattern. This periodic structure simplifies timing synchronization compared to continuous monitoring, as the receiver only needs to synchronize to the periodic pattern rather than continuously track the signal.
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
This approach enhances the reliability of detecting secondary signals and improves the accuracy of OSNR measurement by selectively controlling the detection and measurement timing based on a predetermined superimposition pattern, reducing the need for complex timing synchronization and improving real-time monitoring performance.
Implementation Method 1
The photodetector may be configured to convert light having passed through the tunable optical filter into an electrical signal
Data Source
AI summary
An optical receiver receives signal light obtained by superimposing a second signal to a first signal according to a predetermined superimposition pattern. In the optical receiver, a tunable optical filter allows a part of a spectrum of the received light to pass, and a photodetector converts the transmission light into an electrical signal. A filter controller controls a center transmittance frequency of the tunable optical filter in response to a superimposed period and a non-superimposed period of the second signal identified based on the electrical signal. A superimposed signal detector detects the second signal based on the electrical signal obtained in response to the control of the tunable optical filter during the superimposed period. An optical signal-to-noise ratio (OSNR) calculator calculates an OSNR of the signal light based on the electrical signal obtained in response to the control of the tunable optical filter during the non-superimposed period.