Spectrum-Sliced WDM-PON Using Broad-Spectrum Source
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Solution Overview
Problem
Conventional WDM-based optical networks are costly due to the need for wavelength-controlled narrow-spectrum light sources, such as DFB laser diodes, at each optical network unit (ONU), and suffer from low security and scalability issues due to broadcasted downstream signals and complex TDMA protocols.
Innovation Solution
A bidirectional spectrally-sliced WDM-PON system using passive devices like arrayed-waveguide gratings and broad-spectrum sources, which slice and route downstream and upstream signals in specific wavelength channels, reducing the need for precise wavelength control and enabling independent channel operation for each ONU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wavelength-controlled narrow-spectrum light sources (DFB laser diodes) are used at each ONU, then WDM-based optical networks can provide dedicated wavelength channels, but the system cost increases significantly
Solution Approach 1:
The patent uses a single broad-spectrum light source at the OLT to generate all wavelength channels, which are then copied and distributed to multiple ONUs through wavelength-selective switches. Each ONU receives a copy of the appropriate wavelength channel without needing its own narrow-spectrum laser, significantly reducing system cost while maintaining dedicated channel functionality
Solution Approach 2:
The broad-spectrum light source performs multiple functions by generating all required wavelength channels simultaneously. A single device replaces multiple narrow-spectrum lasers, and the wavelength-selective switch routes different wavelength copies to different ONUs, achieving multi-functionality that reduces overall system complexity and cost
2Reliability
If wavelength-specific precision-controlled narrow-spectrum light sources are installed at large numbers of ONUs, then dedicated wavelength channels are provided, but installation and maintenance complexity increases
Solution Approach 1:
Instead of installing precision-controlled narrow-spectrum lasers at each ONU, the system generates one broad-spectrum signal and creates wavelength-specific copies at the OLT. These copies are distributed through the network, eliminating the need for complex wavelength control and temperature stabilization mechanisms at remote ONU locations
Solution Approach 2:
The wavelength-selective switch acts as an intermediary that performs wavelength routing and copying functions centrally at the OLT. This mediator device handles all wavelength control complexity in one location rather than distributing it across multiple ONUs, simplifying installation and maintenance
3Adaptability or versatility
If TDM-PON uses optical power splitter and broadcasted downstream signals, then point-to-multipoint architecture is achieved, but security is compromised
Solution Approach 1:
The patent segments the broadcast downstream signal into multiple wavelength-specific channels using wavelength division multiplexing. Each ONU receives only its assigned wavelength channel through wavelength-selective filtering, preventing other users from accessing or intercepting other channels' data, thus maintaining security while preserving point-to-multipoint architecture
Solution Approach 2:
Each wavelength channel is assigned to a specific ONU with unique local quality characteristics (specific wavelength). This wavelength-specific assignment ensures that each user's data is confined to its own spectral channel, providing security through spectral isolation while maintaining the ability to serve multiple users simultaneously
4Productivity
If TDM-PON uses TDMA protocols for upstream reception, then bandwidth sharing is achieved, but protocol complexity increases
Solution Approach 1:
The patent moves from time-division multiplexing (TDMA) in the time domain to wavelength-division multiplexing in the spectral domain. Each ONU is assigned a specific wavelength channel for upstream communication, eliminating the need for complex TDMA synchronization and timing protocols while maintaining efficient bandwidth sharing through spectral allocation
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 solution provides a cost-effective, secure, and scalable optical communication system with symmetrical bandwidth for both downstream and upstream data, reducing maintenance costs and allowing flexible protocol adaptation and bandwidth upgrades.
Implementation Method 1
The wavelength filter includes a plurality of first branching ports each associated with a specific wavelength channel
Implementation Method 2
a bidirectional amplifier configured to receive the downstream spectrum-sliced signal from the first common port and to send an amplified downstream spectrum-sliced signal to a remote node
Data Source
AI summary
An optical communication system includes a first wavelength filter, a bidirectional amplifier, and a second wavelength filter. The first wavelength filter can receive a downstream broad-spectrum signal and output a downstream spectrum-sliced signal in response to the downstream broad-spectrum signal. The bidirectional amplifier can amplify the downstream spectrum-sliced signal. The second wavelength filter can receive the amplified downstream spectrum-sliced signal from the bidirectional amplifier and route the amplified downstream spectrum-sliced signal. The second wavelength filter can also output an upstream spectrum-sliced signal in response to an upstream broad-spectrum signal. The bidirectional amplifier can amplify the upstream spectrum-sliced signal to product an amplified upstream spectrum-sliced signal that is subsequently routed by the first wavelength filter.