Time Synchronization System Using Wavelength Division on Two-Core Fibers
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Solution Overview
Problem
Existing time synchronization methods using one-core bidirectional optical fibers are inefficient and costly, especially when applied between communication apparatuses already depleted of core wires, and they struggle to maintain synchronization due to fluctuations in optical fiber characteristics and length.
Innovation Solution
A two-core bidirectional time synchronization system that transmits and receives pulse signals of different wavelengths through separate optical fibers, allowing for the calculation and correction of propagation delays to ensure synchronized timing, even with fluctuations in optical characteristics and fiber length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If one-core bidirectional optical fiber is used for time synchronization, then time synchronization accuracy is improved, but device complexity and cost increase due to occupying an existing optical fiber
Solution Approach 1:
The patent divides the time synchronization function into separate forward and backward transmission paths using two different wavelengths (λ1 and λ2) on the same optical fiber. By segmenting the synchronization process into distinct wavelength channels, the system achieves accurate one-way delay measurement without occupying additional physical fiber cores, thus resolving the contradiction between synchronization accuracy and device complexity.
Solution Approach 2:
The patent transitions from spatial segmentation (using separate fiber cores) to spectral segmentation (using different wavelengths) for bidirectional time synchronization. This dimensional change from spatial to spectral domain allows simultaneous forward and backward synchronization signals to coexist on the same optical fiber without interference, eliminating the need to occupy additional fiber resources while maintaining high synchronization accuracy.
2Measurement precision
If optical fiber characteristics fluctuate due to environmental changes, then propagation delay varies, but synchronization accuracy is maintained through delay correction
Solution Approach 1:
The patent implements a feedback mechanism where the second communication apparatus measures the actual propagation delay of synchronization signals traveling through the optical fiber and sends delay correction information back to the first apparatus. This closed-loop feedback system continuously compensates for propagation delay variations caused by environmental changes in optical fiber characteristics, maintaining synchronization accuracy despite fiber instability.
Solution Approach 2:
The patent performs preliminary measurement of propagation delay using test synchronization signals before actual time synchronization operations. By pre-characterizing the optical fiber's propagation properties and storing this information for later compensation, the system proactively prepares for and mitigates the effects of environmental fluctuations on fiber characteristics, ensuring stable synchronization performance.
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 approach enables accurate and cost-effective time synchronization between communication apparatuses using existing two-core optical fibers, reducing the need for additional infrastructure and maintaining synchronization despite changes in optical fiber characteristics and length.
Implementation Method 1
a first pulse signal of a first wavelength and a second pulse signal of a second wavelength different from the first wavelength to the second communication apparatus through the first optical fiber
Implementation Method 2
calculate a propagation delay amount in the first optical fiber from a proportional relationship between a propagation delay time difference between the first pulse signal and the fourth pulse signal
Data Source
AI summary
[Problem] To synchronize timings of transmitting and receiving a pulse signal (1 PPS signal) at a constant interval between communication apparatuses even in a case where an optical fiber connecting the communication apparatuses fluctuates in an optical characteristic and an optical fiber length.[Solution] The time synchronization system 20 transmits and receives a pulse signal at a constant interval between a local apparatus L (apparatus L) and a remote apparatus R (apparatus R) connected through the two-core bidirectional optical fibers F1 and F2 to synchronize time. A propagation delay amount τ1 in the fiber F1 is calculated, from a proportional relationship between T1 and T2 and a proportional relationship of τud and τ1, where T1 represents a propagation delay time difference between a pulse signals P1 and P4 of an identical wavelength λ1 returned after transmitting a pulse signal P1 of wavelength λ1 and a pulse signal P2 of wavelength λ2 different from λ1 to the remote apparatus R, T2 represents a propagation delay time difference between the pulse signal P1 of wavelength λ1 and a pulse signal P3 of wavelength λ2, and τud represents the round-trip delay time between the apparatuses L and R. The pulse signals P1 and P2 are transmitted with a time difference td corresponding to a difference between the current and last calculated propagation delay amounts τ1 being set so that the difference is zero.