Wireless Optical Time Comparison Using Phase-Modulated Antennas
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Solution Overview
Problem
Conventional time comparison systems face challenges in determining a time difference between clocks placed far apart with both low cost and high accuracy, as they either occupy expensive resources like dark fibers or are susceptible to interference.
Innovation Solution
A time comparison system that uses an intermediate station with an optical antenna to transmit and receive optical signals, employing optical complex amplitude modulation and phase modulation to determine the direction and propagation delay of comparative stations, allowing for wireless communication and accurate time difference calculation without dedicated optical fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Optical Time Transfer (OTT) system using optical fiber is used to compare times of clocks far apart, then time comparison accuracy is improved, but running cost increases due to occupying dark fiber resources
Solution Approach 1:
The patent replaces the optical fiber-based mechanical transmission system with a wireless optical communication system. Instead of using physical optical fibers to transmit time signals between clocks, the invention uses wireless optical signals (laser beams) transmitted through the atmosphere or vacuum, eliminating the need for dedicated optical fiber infrastructure and reducing running costs while maintaining time comparison accuracy
Solution Approach 2:
The patent introduces an intermediary wireless optical signal transmission medium between the clocks. Rather than directly connecting clocks through optical fibers, the system uses wireless optical signals as an intermediary carrier to transmit time information, enabling time comparison without occupying expensive dark fiber resources
2Loss of energy
If GPS-CV system is used to compare times of clocks far apart, then running cost is reduced, but measurement reliability deteriorates due to susceptibility to interference waves and disturbance waves
Solution Approach 1:
The patent replaces the radio frequency-based GPS system with an optical wireless communication system. Instead of using electromagnetic radio waves that are susceptible to interference, the invention uses optical signals (laser beams) for time transmission, which are less prone to electromagnetic interference while maintaining low running costs
Solution Approach 2:
The patent changes the fundamental parameter of signal transmission from radio frequency electromagnetic waves to optical frequency electromagnetic waves. This parameter change transitions the system from GPS-CV's vulnerable RF band to the optical band, which offers better resistance to electromagnetic interference and disturbance waves while keeping operational costs low
3Loss of energy
If wireless optical communication is used to compare times of clocks, then running cost is reduced and adaptability is improved, but device complexity increases due to need for optical antennas and modulation systems
Solution Approach 1:
The patent designs the optical antenna system to perform multiple functions: transmitting optical signals, receiving reflected optical signals, and enabling two-way communication. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing device complexity while achieving wireless operation and cost reduction
Solution Approach 2:
The patent implements a system where each clock station equipped with optical antenna can independently transmit and receive optical signals without requiring complex external infrastructure. The stations perform their own time comparison measurements autonomously, reducing the need for complex centralized control systems and lowering overall device complexity
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
Enables the determination of time differences between distant clocks with high accuracy at a low cost, reducing running costs and avoiding interference issues, while operating in environments with electromagnetic noise.
Implementation Method 1
an optical antenna configured to transmit, to the plurality of comparative stations, an optical signal on which a time of the clock is superimposed and to receive reflected light of the optical signal
Implementation Method 2
a reflection unit configured to reflect, in a direction of the intermediate station, an optical signal from the intermediate station received by the optical antenna
Data Source
AI summary
[Problem] To determine a time difference between clocks which, for example, are placed far apart from each other with high accuracy at low cost.[Solution] In a time comparison system 20, an intermediate station 21 disperses a single optical signal 21c in the spatial region using the optical complex amplitude modulation to simultaneously transmit the optical signal 21c to a plurality of comparative stations 22 and 23 apart from each other. The intermediate station 21 transmits the optical signal 21c while changing the transmission angle using phase modulation, performs intensity scanning for the reflected light c1 of the optical signal 21c, and detects the peak intensity to determine the directions of the comparative stations 22 and 23. The reflected light c1 of the optical signal 21c transmitted to the comparative stations 22 and 23 of which the direction have been determined, is detected to determine a round-trip propagation delay time between the intermediate station 21 and each of the comparative stations 22 and 23. The difference calculation unit 25 calculates a sum of time difference between each of times to and tb associated with the comparative stations 22 and 23 and the time tc associated with the intermediate station 21, and the determined propagation delay time to determine time information of each of the comparative stations 22 and 23. Based on the result of subtracting, from the time information of the comparative stations 22, the time information of the comparative stations 23, the time difference between the comparative stations 22 and 23 is determined.