Optical Subcarrier Synchronization Using DSP-Based Clock Locking
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Solution Overview
Problem
Optical system components face challenges in processing multiplexed subcarriers due to differing frequency rates, leading to improper processing and potential interference during data transmission.
Innovation Solution
Implementing a technique where the optical system and leaf systems use coherent detection and digital signal processing to synchronize clock frequencies, allowing each leaf system to adjust and lock onto the correct transmit frequency of incoming subcarriers, preventing spectral overlap and enabling proper demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If each subcarrier is transmitted at its own respective frequency rate, then frequency multiplexing capacity is improved, but processing accuracy deteriorates due to frequency misalignment
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the sampling frequency and clock rates at receiving components to match the actual transmit frequencies of incoming subcarriers. The receiving component detects frequency offsets and modifies its operating parameters (sampling rate, clock frequency) to align with the transmitted signal parameters, thereby maintaining processing accuracy despite frequency variations in multiplexed subcarriers.
2Device complexity
If clock frequencies are not synchronized, then system complexity is reduced, but data transmission reliability deteriorates due to spectral overlap and interference
Solution Approach 1:
The patent implements feedback mechanisms where receiving components continuously monitor the frequency of incoming subcarriers and generate control signals to adjust their clock frequencies accordingly. This closed-loop feedback system detects frequency offsets, computes correction values, and applies real-time adjustments to maintain synchronization, ensuring reliable data transmission without requiring complex pre-synchronization infrastructure.
Solution Approach 2:
The patent applies preliminary action by performing frequency detection and clock adjustment at the receiving end before data processing occurs. The receiving component proactively detects frequency offsets in incoming subcarriers and adjusts its sampling clock in advance, ensuring that subsequent data processing operations are performed on properly synchronized signals, thereby preventing spectral overlap and interference.
3Object-affected harmful factors
If frequency locking is implemented, then spectral overlap is prevented, but processing time increases due to iterative frequency detection and adjustment
Solution Approach 1:
The patent applies partial action by implementing frequency locking only for the specific subcarrier being processed at each receiving component. Instead of synchronizing all components to a single master clock, each component performs frequency detection and adjustment only for its assigned subcarrier, reducing overall processing time while still preventing spectral overlap through targeted frequency alignment.
Data Source
AI summary
Methods, systems, transceivers, and apparatus are included for clock synchronizing an optical system and multiple leaf systems. In some implementations, a transceiver includes a receiver and a transmitter. The receiver includes an optical hybrid circuit operable to receive a first modulated optical signal and local oscillator light and to supply optical mixing products based on the first modulated optical signal and the local oscillator light. A photodiode circuit operable to supply an electrical signal based on the optical mixing products. An analog-to-digital conversion circuitry operable to supply digital signals based on the electrical signal. A digital signal processor operable to generate a supply signal based on the digital signals and provide the supply signal to a reference clock circuit for generating a clock signal. The transmitter is operable to output a second modulated optical signal that includes a timing of data based on the clock signal.