Digital Optical Transmitter for Narrowcast Signal Capacity
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Solution Overview
Problem
The existing overlay system architecture is inadequate to meet the growing demand for narrowcast services due to limitations in the number of narrowcast channels and fiber capacity, leading to increased costs and inefficiencies in signal level management.
Innovation Solution
The system re-digitizes narrowcast analog signals after QAM modulation and upconversion, replacing analog narrowcast transmitters with digital ones, allowing for increased narrowcast channels without requiring additional amplifiers or costly fiber upgrades, and independently managing signal levels for cost-effective expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If analog narrowcast transmitters are used in the overlay system, then the system can deliver narrowcast services, but the number of narrowcast channels is limited and fiber capacity is insufficient
Solution Approach 1:
The patent replaces the analog narrowcast transmitter system with a digital signal processing system. Specifically, it uses a digitizer to convert analog RF signals to digital baseband signals, then uses digital signal processing to generate multiple narrowcast channels. This substitution of analog mechanical/electrical systems with digital systems enables increased channel capacity without requiring additional fiber infrastructure.
Solution Approach 2:
The patent changes the signal representation from analog continuous signals to digital discrete signals. By converting the narrowcast signals to digital baseband signals and processing them in the digital domain, the system can multiplex multiple channels more efficiently. This parameter change from analog to digital domain enables increased adaptability and number of narrowcast channels within the existing fiber capacity.
2Adaptability or versatility
If additional amplifiers are installed to increase narrowcast capacity, then more channels can be supported, but the cost increases significantly
Solution Approach 1:
The patent creates digital copies of the baseband signal to generate multiple narrowcast channels. Instead of using additional physical amplifiers to increase capacity, the system digitally processes and replicates the signal in the digital domain, then modulates multiple channels onto the existing fiber infrastructure. This copying approach in the digital domain is cost-effective compared to adding physical amplifiers.
Solution Approach 2:
The patent substitutes the mechanical approach of adding amplifiers with a digital signal processing approach. By using digitizers and digital signal processors, the system can increase channel capacity through software-based signal generation and multiplexing, eliminating the need for costly hardware amplifiers and reducing overall system cost.
3Productivity
If the overlay system is expanded to meet growing narrowcast demand, then service capacity increases, but signal level management becomes more complex and costly
Solution Approach 1:
The patent replaces analog signal level management with digital signal processing. The digitizer converts analog RF signals to digital baseband signals, where signal levels can be precisely controlled through digital processing. This substitution eliminates the complexity of managing multiple analog signal levels and provides more straightforward digital control mechanisms.
Solution Approach 2:
The patent introduces a digitizer as an intermediary device between the analog RF domain and the digital processing domain. This digitizer serves as a mediator that converts analog signals to digital form, enabling simplified digital signal level management. The digital baseband processing then provides precise and flexible control over signal levels without the complexity of analog level management.
Data Source
AI summary
Methods and apparatuses are provided to modify existing overlay system architectures in a cost effective manner to meet the growing demand for narrowcast services and to position the existing overlay systems for additional future modifications. The implementations of the improved overlay system of this disclosure re-digitize narrowcast analog signals after they have been QAM modulated and upconverted to RF frequencies and replace the analog narrowcast transmitters with digital narrowcast transmitters. In the fiber nodes, the received narrowcast signals are converted back to analog signals and combined with analog broadcast signals for transmission to the service groups.