Coherent Receiver Noise Characterization via Signal Power Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional methods for measuring optical signal-to-noise ratio (OSNR) in coherent optical receivers are inaccurate due to the inclusion of receiver noise, which becomes a significant percentage of total noise at higher OSNR values, making previous estimation techniques unreliable.
Innovation Solution
The method involves varying the input signal power level to an optical receiver to isolate receiver noise from amplified spontaneous emission (ASE) noise, allowing for a more accurate assessment of optical link quality by characterizing components such as Shot noise, Relative Intensity Noise, and thermal noise, and using a digital signal processor to derive a precise OSNR estimate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional OSNR measurement methods are used in coherent optical receivers, then the measurement process is simple, but the measurement precision deteriorates due to inclusion of receiver noise
Solution Approach 1:
The patent segments the total noise into distinct components: ASE noise and receiver noise. By measuring total noise at two different signal power levels and subtracting the receiver noise component (which remains constant), the method isolates the ASE noise contribution to calculate accurate OSNR. This segmentation approach resolves the contradiction by enabling precise measurement through systematic noise decomposition.
Solution Approach 2:
The patent performs preliminary characterization of receiver noise by measuring the noise floor at a first signal power level before proceeding to OSNR calculation. This preliminary measurement of receiver noise components (shot noise, thermal noise, RIN) is stored and subsequently used to correct the OSNR measurement, eliminating the need for complex real-time separation and simplifying the overall measurement process while maintaining high precision.
2Measurement precision
If signal power level is varied to separate noise components, then OSNR measurement accuracy improves, but measurement time increases
Solution Approach 1:
The patent performs receiver noise characterization as a preliminary action during system setup or calibration phases. The measured receiver noise parameters are stored and reused for subsequent OSNR measurements, eliminating the need to repeatedly vary signal power levels for each measurement. This approach achieves high measurement precision while minimizing measurement time for actual OSNR assessments.
Solution Approach 2:
The patent measures total noise at two different signal power levels to fully characterize and separate noise components. While this requires additional measurement points compared to single-level methods, it provides complete noise decomposition enabling accurate OSNR calculation. The excessive measurement action (two power levels) ensures precise separation of ASE and receiver noise contributions.
Data Source
AI summary
Optical signal to noise ratios that more accurately characterize optical link noise are determined. As noise induced by an optical receiver does not generally vary with an input optical signal power, a power of an incoming optical signal is varied at the receiver. A resulting variation in noise measure represents a variation in link noise and does not include any variation caused by receiver noise, as receiver noise does not generally vary with optical signal power. Thus, the contribution of optical link noise can be discerned from other noise induced by the receiver itself. A more accurate characterization of optical link performance is thus provided.