Digital Radio-Over-Fiber Transmission for Remote RF Amplification
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Solution Overview
Problem
The quality of optical transmission in radio-over-fiber systems is compromised by noise, non-linearities, and attenuation, leading to high losses and the need for sophisticated modulation techniques and costly equipment, especially when transmitting analogue radio frequency signals over wide distances.
Innovation Solution
Transmitting data signals digitally over optical connections to remote amplification stages, where they are converted back to analogue signals for amplification using mature analogue amplifiers, thereby reducing signal degradation and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analogue radio frequency signals are transmitted over optical fibers, then signal transmission is achieved, but transmission quality deteriorates due to noise, non-linearities, and attenuation
Solution Approach 1:
The patent changes the fundamental parameter of signal representation from analogue to digital domain. By converting analogue radio frequency signals into digital baseband signals for optical transmission, the system transforms the signal characteristics to be immune to optical fiber impairments like noise, non-linearities, and attenuation, thereby resolving the transmission quality deterioration issue
Solution Approach 2:
The patent replaces the traditional analogue radio frequency transmission mechanism with a digital baseband transmission mechanism over optical fibers. This substitution eliminates the direct interaction between analogue RF signals and optical fiber impairments, as the digital signals are processed in the baseband domain and only converted to RF at the receiving end
2Ease of manufacture
If intensity modulation and direct detection is used for optical transmission, then transmission simplicity is achieved, but costly modulators and modulator drivers are required
Solution Approach 1:
The patent changes the modulation parameter from intensity modulation of analogue RF signals to digital baseband modulation. By transmitting digital signals in the baseband domain, the system can use simpler optical modulators that do not require expensive RF modulator drivers, as the modulation is performed on digital baseband signals rather than analogue RF signals
Solution Approach 2:
The patent extracts the modulation function from the optical transmission path and moves it to the digital baseband processing domain. This separation allows the optical modulators to operate with simpler, less expensive components while the complex modulation logic is handled in the digital domain where it is more efficient
3Extent of automation
If double side band modulation is used, then modulation is achieved, but chromatic dispersion causes frequency and length dependent suppression of radio frequency power
Solution Approach 1:
The patent changes the fundamental parameter of signal domain from analogue RF to digital baseband. By performing modulation in the digital baseband domain and only converting to RF after optical transmission, the system eliminates chromatic dispersion effects that plague analogue RF modulation, as digital baseband signals are much less susceptible to dispersion-induced frequency and length dependent suppression
Solution Approach 2:
The patent performs all necessary modulation and signal processing actions in advance in the digital baseband domain before optical transmission. This preliminary digital modulation avoids the problems of analogue RF modulation subject to chromatic dispersion, as the signal is already fully modulated in the baseband domain and simply transported optically without further RF modulation
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
This method enables low-loss, high-quality transmission of radio signals across wide distances using digital data transmission and conventional analogue amplifiers, improving reliability and reducing electronic efforts.
Implementation Method 1
converting electrical digital data signals into optical digital data signals
Implementation Method 2
converting the optical digital data signals back into electrical digital data signals
Implementation Method 3
conversion into an analogue radio frequency signal may be performed by a suitable reconstruction filter
Data Source
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AI summary
The invention concerns a method for transmission of data signals from a transmitting device (BS) to a receiving device (RAH1), wherein said data signals are transmitted over an optical connection (OF1) from the transmitting device (BS) to the receiving device (RAH1), electrical data signals are digitally modulated in the transmitting device (BS) resulting in electrical digital data signals, the electrical digital data signals are converted into optical digital data signals in the transmitting device (BS), the optical digital data signals are converted into electrical digital data signals in the receiving device (RAH1), the electrical digital data signals are converted into electrical analogue data signals in the receiving device (RAH1), and said electrical analogue data signals are amplified in an analogue radio frequency power amplifier (PA), a transmitting device and a receiving device therefor.