WDM-PON Tunable Laser Initialization via Optical Layer Channel
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Solution Overview
Problem
Current WDM-PON systems face challenges in automatically tuning ONT laser transmitters to specific wavelengths for upstream communication, with existing solutions being protocol-specific, power-intensive, and slow, and risking interference with other ONTs due to inadequate wavelength splitter isolation.
Innovation Solution
The system employs an OLT and ONT with a Laser shutdown function and Signal detect function to establish a communications channel, allowing the OLT controller to generate and transmit laser set-up information via wavelength splitters, enabling the ONT controller to automatically tune the ONT laser transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If higher layer communications are used to carry control information for wavelength tuning, then wavelength tuning functionality is achieved, but the solution becomes protocol-specific and cannot be used when Ethernet functionality or other layer 2 protocols are not present
Solution Approach 1:
The patent introduces an optical layer intermediary mechanism using the OLT's laser shutdown function and ONT's signal detect function as a mediator to establish a communication channel. This intermediary operates at the optical layer (layer 1) rather than depending on higher layer protocols, enabling wavelength tuning information to be transmitted without requiring Ethernet or other layer 2 protocols, thus achieving protocol independence while maintaining functionality
Solution Approach 2:
The patent replaces the mechanical/software-based higher layer communication system with an optical-based layer 1 communication mechanism. By substituting the electronic protocol-dependent communication with optical signal detection and laser shutdown functions, the system eliminates dependency on Ethernet or other layer 2 protocols while achieving the same wavelength tuning control objective
2Measurement precision
If the ONT laser transmitter tests every US wavelength to find the correct one, then wavelength tuning is achieved, but the process consumes high power and takes quite long time (e.g., 1 minute)
Solution Approach 1:
The patent applies preliminary action by having the OLT pre-determine and transmit the correct upstream wavelength information to the ONT before the ONT begins transmission. Instead of the ONT randomly testing wavelengths, the OLT controller calculates the appropriate wavelength based on system configuration and communicates it to the ONT in advance through the optical layer communication channel, allowing the ONT to directly tune to the correct wavelength without time-consuming trial and error
Solution Approach 2:
The patent implements a feedback mechanism where the OLT controller receives information about the ONT's downstream wavelength and calculates the corresponding upstream wavelength, then feeds back this wavelength information to the ONT through the optical communication channel. This feedback loop enables the ONT to accurately determine the required upstream wavelength without random testing, significantly reducing tuning time while maintaining wavelength accuracy
3Measurement precision
If the ONT laser transmitter tests every US wavelength, then wavelength tuning is achieved, but it risks corrupting the US communications of other ONTs if the isolation of the AWG wavelength splitter is inadequate
Solution Approach 1:
The patent applies preliminary action by having the OLT pre-calculate and communicate the correct upstream wavelength to each ONT before transmission begins. This eliminates the need for ONTs to test multiple wavelengths, preventing any potential interference to other ONTs that might occur during wavelength scanning or testing, while still achieving accurate wavelength configuration
Solution Approach 2:
The patent extracts the wavelength determination function from the ONT side and relocates it to the OLT side. The OLT controller performs the wavelength calculation and information transmission, removing the need for the ONT to engage in wavelength testing that could cause interference. This extraction of the tuning control function eliminates the harmful interference effect while maintaining wavelength accuracy
Data Source
AI summary
A wavelength-multiplexed passive optical network (WDM-PON) and a method are described herein for setting-up (e.g., wavelength tuning, power tuning) an ONT laser by establishing a communications channel on an optical layer between an optical line terminal (OLT) and an optical network termination (ONT). The communications channel is established by utilizing the OLT's laser shutdown function and the ONT's signal detection function.