Optical Transfer Function Separation Using Frequency Offsets
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Solution Overview
Problem
Existing methods for estimating transfer functions in transmitter-receivers require additional noise sources and multiple processing steps, and struggle to separate phase characteristics effectively.
Innovation Solution
A method that calculates a composite transfer function combining transmission and reception functions based on frequency offsets, allowing separation into individual transfer functions using amplitude and phase characteristics dependent on these offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a white noise source different from the transmitter-receiver is used to obtain a temporary reception-side transfer function, then the reception-side transfer function can be estimated, but the number of processing steps is increased
Solution Approach 1:
The invention extracts and utilizes the known signal sequence that is already available in the transmission-reception system. Instead of introducing a separate white noise source, the method extracts the known signal sequence from the transmitted signal and uses it to directly estimate both transmission and reception transfer functions, thereby eliminating unnecessary processing steps while maintaining estimation accuracy
Solution Approach 2:
The known signal sequence serves multiple functions: it is used to estimate both the transmission transfer function and the reception transfer function simultaneously. This multi-functional approach replaces the conventional two-step process (first estimating reception transfer function with white noise, then using that result for transmission function estimation), reducing overall processing complexity
2Measurement precision
If averaging the transfer functions when changing the frequency offset is used to reduce mixing of phase characteristics, then phase characteristics separation is improved, but it is difficult to completely separate the phase characteristics depending on the phase characteristics on the receiver side
Solution Approach 1:
The invention segments the transfer function estimation process into independent estimation of transmission and reception transfer functions using the known signal sequence. By dividing the estimation into separate components that can be independently calculated, the method achieves complete separation of phase characteristics without relying on averaging techniques that may fail to completely separate characteristics depending on receiver side phase characteristics
Data Source
AI summary
A transfer function estimation device includes a composite transfer function calculation unit that calculates a composite transfer function which is obtained by combining a transmission transfer function that affects a signal transmitted by an optical transmitter and a reception transfer function that affects a signal received by an optical receiver in each of frequency offsets that are differences between a frequency of a carrier wave input to an optical modulation unit in the optical transmitter and a frequency of a carrier wave input to an optical demodulation unit in the optical receiver based on a signal transmitted by the optical transmitter and a signal received by the optical receiver, and a transfer function separation unit that calculates the transmission transfer function and the reception transfer function from the composite transfer function based on dependency of the composite transfer function on the frequency offset.