Optical Demodulator for Mixed Carrier Signal Separation
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Solution Overview
Problem
Current optical data transmission systems face challenges in achieving high spectral bandwidth efficiency while maintaining low complexity, as they require expensive components and suffer from signal quality degradation due to fiber impairments like filter distortions and chromatic dispersion, necessitating complex systems and separate filters for each channel.
Innovation Solution
A method and system that transmit and receive modulated signals using mixed carrier frequencies, allowing for simple signal separation with a single optical demodulator and electrical-optical converter, and utilizing orthogonal signals to transmit within a narrow optical channel, reducing the need for multiple filters and converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wavelength division systems split high data rate signals into multiple signals with lower data rates, then signal quality is improved by overcoming impairments scaling with data rate, but device complexity increases due to necessary filters and different demodulators for each channel
Solution Approach 1:
The patent combines multiple wavelength channels into a single composite signal that is transmitted through one optical fiber. At the receiver, a single demodulator processes all channels by exploiting the periodic transfer function of a delay interferometer, eliminating the need for separate filters and demodulators for each channel while maintaining signal quality
Solution Approach 2:
A single delay interferometer with periodic transfer function serves multiple wavelength channels simultaneously. The interferometer's periodic response allows it to demodulate multiple channels using the same device, making it a universal demodulator that replaces multiple channel-specific demodulators
2Reliability
If orthogonal frequency-diversity modulation OFDM or polarisation multiplex diversity are used to reduce channel symbol rate and overcome impairments, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple modulation channels into a single wavelength signal that carries multiple data streams. By using orthogonal signaling within a single wavelength and a single demodulator, it achieves diversity without requiring multiple separate transmission paths or complex multiplexing hardware
3Productivity
If high data rates are transmitted through optical channels, then productivity is improved, but device complexity increases due to requirement of high bandwidths and expensive components
Solution Approach 1:
The patent segments the high data rate signal into multiple lower-rate wavelength channels that are combined and transmitted together. Each channel operates at a lower symbol rate, allowing the use of simpler, less expensive components while achieving high aggregate data rates through the combined channels
Solution Approach 2:
The patent changes the operating parameters by using multiple wavelengths with lower individual data rates instead of a single high data rate wavelength. This parameter change allows the system to achieve high total bandwidth while using components designed for lower, more manageable data rates
Data Source
Figure 1~3
Figure 4~5
AI summary
The arrangement includes a transmitter (1-6) with two optical sources (1, 2) generating two optical carrier signals (L1, L2) having different frequencies. The optical carrier signals (L1, L2) are combined and divided in a first coupler (2) and fed to carrier signal inputs of two modulators (4, 5). The mixed carrier signals (L1 + jL2, jL1 + L2) are separately modulated by two modulation signals (a(t)) and (b(t)) and the modulated signals ((A1 +jA2), (jB1 +B2)) are combined in a first combiner and emitted as transmission signal (X(t)). Only on demodulator is necessary to regain the modulation signals (a(t), b(t)).