Passive Optical Network Upstream RF Signal Transport
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Solution Overview
Problem
Current point-to-multipoint passive optical network systems are unable to effectively transport upstream RF signals generated by devices like set top boxes and cable modems while simultaneously supporting downstream RF video and bi-directional base-band services, limiting the provision of advanced services such as Video on Demand and Network Digital Video Recorder.
Innovation Solution
The system employs a node operating at optical wavelength λ4 to transmit upstream RF signals, which are de-multiplexed at the central office and routed to an RF Optical Receiver, while also providing bi-directional base-band services, using a configuration that allows four wavelengths to coexist on the PON between the hub and customer premises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a three-wavelength ONU is used to provide downstream RF service, then the system can deliver RF video channels, but it cannot transport upstream RF signals from set top boxes and cable modems
Solution Approach 1:
The patent applies multi-functionality by enabling the ONU to operate at four wavelengths instead of three, allowing it to simultaneously handle downstream RF services (wavelengths λ1 and λ3) and upstream RF signals (wavelength λ4), while maintaining base-band services (wavelength λ2). This universal configuration resolves the limitation where three-wavelength ONUs could only provide downstream RF but not upstream RF transport.
Solution Approach 2:
The patent introduces another dimension by adding a fourth wavelength λ4 to the existing three-wavelength system. This dimensional expansion in the wavelength domain allows the system to accommodate upstream RF signals without interfering with the existing downstream RF and base-band services, effectively resolving the functional limitation through spectral dimensionality.
2Adaptability or versatility
If upstream RF signals are added to the PON system, then advanced video services can be provided, but signal collision and interference occur with existing wavelengths
Solution Approach 1:
The patent applies parameter changes by introducing a new wavelength parameter λ4 for upstream RF signals, distinct from the existing wavelengths λ1, λ2, and λ3. This parameter differentiation in the optical spectrum ensures that upstream RF signals do not collide or interfere with downstream RF video channels or base-band data services, maintaining signal integrity while enabling advanced video services.
Solution Approach 2:
The patent segments the optical spectrum into four distinct wavelength channels, assigning specific functions to each: λ1 and λ3 for downstream RF, λ2 for upstream base-band, and λ4 for upstream RF. This segmentation prevents signal collision by spatially separating different signal types in the wavelength domain, ensuring reliable simultaneous operation of multiple services.
3Productivity
If four wavelengths are used to coexist on the PON, then simultaneous transport of multiple services is achieved, but system complexity increases
Solution Approach 1:
The patent merges multiple service functions into a unified four-wavelength PON architecture, where downstream RF video, upstream base-band data, and upstream RF signals all coexist on the same physical infrastructure. By combining these services with coordinated wavelength assignment and WDM multiplexing, the system achieves high productivity through simultaneous service delivery while managing complexity through integrated wavelength coordination.
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 configuration enables the simultaneous transport of upstream RF signals and downstream RF video and bi-directional base-band services, overcoming the limitations of existing systems and allowing for the provision of advanced video services.
Implementation Method 1
A Wavelength Division Multiplexer (WDM) is typically used to separate the optical wavelengths
Implementation Method 2
The Optical Transmitter transmits data downstream to the ONUs on an optical wavelength
Implementation Method 3
The Optical Receiver receives data upstream on an optical wavelength from the ONUs
Implementation Method 4
an Optical Line Terminal (OLT) or Optical Line Termination (OLT) connected via fiber to a 1:n passive optical splitter
Implementation Method 5
This RF frequency band comprising analog and digital channels is modulated into an optical carrier at wavelength λ3 and inserted into the PON using a WDM
Implementation Method 6
At the subscriber side, the wavelength is separated using a WDM and converted into RF for distribution within the customer premises
Data Source
AI summary
A system for providing bi-directional RF services over a point-to-multipoint Passive Optical Network (PON). A system that can transport upstream RF signals generated by devices such as a set top box or a cable modem, through a passive Optical Network while simultaneously supporting downstream RF video and bi-directional base-band services on the PON.