Optical Filter Assembly for RIN Reduction in Communication Signals
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Solution Overview
Problem
Existing systems for optically filtering communication signals using a pair of optical filters face challenges such as relative intensity noise (RIN) reduction, complex calibration, and significant space and power consumption.
Innovation Solution
An optical filter assembly that splits an optical beam into two complementary modulated beams, using a single optical filter to filter the beams for a target frequency band and balanced detectors to convert and subtract noise, thereby reducing RIN and improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pair of optical filters is used to suppress RIN, then the signal to noise ratio is improved, but the device complexity and calibration difficulty increase
Solution Approach 1:
The patent combines the functions of two separate optical filters into a single optical filter. The single filter is configured to receive both a first optical signal and a second optical signal, and simultaneously output a first filtered optical signal and a second filtered optical signal. This merging approach maintains the RIN suppression capability while reducing device complexity and eliminating the need for complex balancing and tuning between multiple filters.
2Reliability
If a pair of optical filters is used to suppress RIN, then the signal to noise ratio is improved, but the space occupation and power consumption increase
Solution Approach 1:
The patent merges multiple optical filter functions into a single optical filter device, which directly reduces the number of components, occupied space, and power consumption. The single filter performs the work of multiple filters while consuming less power and occupying less space, thereby resolving the contradiction between reliability improvement and energy/space consumption.
3Reliability
If a pair of optical filters is used to suppress RIN, then the signal to noise ratio is improved, but the calibration and tuning process becomes complex
Solution Approach 1:
The patent simplifies the calibration process by combining multiple filter functions into a single optical filter. This eliminates the need for complex balancing and tuning between multiple filters, making the system easier to operate and maintain while preserving the signal to noise ratio improvement.
4Productivity
If optical filtering is applied to broadband signals, then multiple narrowband signals can be separated, but relative intensity noise is introduced
Solution Approach 1:
The patent uses a single optical filter to simultaneously process multiple optical signals, maintaining the signal separation capability while reducing the introduction of relative intensity noise. The unified filter approach provides more consistent filtering performance across multiple signals compared to using separate filters.
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
The solution effectively reduces RIN, simplifies calibration, and reduces the cost, power consumption, and space requirements compared to conventional systems, while maintaining or improving signal quality.
Implementation Method 1
an optical filter configured to filter the modulated optical beams for a target frequency band
Implementation Method 2
balanced detectors configured to convert the filtered optical beams to electrical signals and subtract noise from the electrical signals
Data Source
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AI summary
There is provided a method and apparatus for optically filtering a communication signal. More specifically, in one embodiment, there is provided an apparatus comprising an optical filter having first and second input ports and first and second output ports, the optical filter being configured to transmit light in a target frequency range to the first output port in response to receiving light at the first input port and being configured to transmit light in the target frequency range to the second input port in response to receiving light at the second output port, and first and second photodiodes, the first diode being located to be illuminated by light from the first output port and the second photodiode being located to be illuminated by light from the second input port.