Frequency-Referenced PON Wavelength Locking With Beat Signals
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Solution Overview
Problem
Conventional frequency division multiplexing systems in passive optical networks face challenges such as high cost, complexity, interference, and vulnerability to uplink reflection, which hinder their ability to support high data rates and emerging applications like 5G, AR, and tactile internet.
Innovation Solution
A system and method for wavelength control in a frequency referenced passive optical network using a central node transceiver to broadcast a reference signal with management information, enabling end nodes to determine and lock to a target frequency through a beating frequency, employing a frequency lock loop unit for accurate and cost-effective wavelength control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time-division multiplexing is used in passive optical networks, then signal collision is avoided, but latency and jitter increase
Solution Approach 1:
The patent uses periodic time slots for upstream transmission where each ONU transmits data in assigned time slots, creating a periodic structure that avoids collision while maintaining deterministic latency characteristics suitable for 5G applications
2Duration of action of stationary object
If frequency division multiplexing is used in passive optical networks, then continuous transmission is enabled, but interference between users occurs
Solution Approach 1:
The patent segments the frequency spectrum into multiple orthogonal frequency subcarriers, where each user is assigned specific subcarriers. This segmentation combined with orthogonal coding allows continuous transmission while eliminating interference between users through mathematical orthogonality
Solution Approach 2:
The patent implements feedback mechanisms where the central office monitors uplink signals and adjusts frequency allocations and power levels to optimize performance and eliminate interference, enabling continuous transmission without harmful interactions
3Productivity
If uplink reflection occurs in SOA devices, then gain ripples are caused, but data signal destruction can occur in extreme cases
Solution Approach 1:
The patent uses external modulators instead of directly modulating the SOA, converting the harmful effect of uplink reflection into a manageable issue. The external modulator placement allows the SOA to operate in a regime where reflections cause minimal gain ripple, and the modulation is applied externally where it does not affect the amplification stability
4Speed
If high bandwidth transceivers are used to match overall bit rate, then data rate capacity is improved, but per-user capacity decreases
Solution Approach 1:
The patent segments the total data rate across multiple orthogonal frequency subcarriers, allowing each user to transmit at lower individual bandwidths while achieving high aggregate data rates through frequency division. This eliminates the need for high bandwidth transceivers at each user while maintaining high per-user capacity
Solution Approach 2:
The patent transitions from time-domain multiplexing to frequency-domain multiplexing, adding a frequency dimension to data transmission. This allows multiple users to transmit simultaneously at lower individual bandwidths while achieving high overall data rates through parallel frequency channels
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
The system provides improved accuracy, flexibility, and low-cost wavelength control, tolerant to uplink reflection, compatible with power-split optical distribution networks, and suitable for non-time division multiplexing architectures, supporting high data rates and diverse applications.
Implementation Method 1
generating a beating frequency by beating the reference signal with an uplink laser signal
Data Source
AI summary
A system is provided for wavelength control in a passive optical network (PON) with point to multi-point (P2MP) topology. The system comprises a central node and a plurality of end nodes. The system comprises a central node transceiver configured for broadcasting to end nodes a reference signal carrying a management information, wherein the management information indicates a target frequency assigned to each end node, and an end node transceiver in each end node. The end node transceiver in each end node is configured for determining the target frequency by extracting the management information from the reference signal, generating a beating frequency by beating the reference signal with an uplink laser signal, and controlling a wavelength of the uplink laser signal to lock to the target frequency based on the beating frequency.