Bi-Directional Optical Link Timing for Uplink-Downlink Separation
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Solution Overview
Problem
Current deep-space communication systems face challenges in maintaining robust communication over long distances and small signal-to-noise ratios, particularly in separating optical uplink and downlink channels due to significant power level differences, which complicates channel separation and requires careful link budget design.
Innovation Solution
A bi-directional optical communication system employing pulsed high-power lasers for beacon signals and active channel separation techniques, where the downlink transmitter is inhibited or light is deflected during beacon pulse arrival to prevent interference, allowing independent optimization of link budgets and using PPM modulation with error coding for reliable data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If continuous wave lasers are used for downlink transmission, then continuous optical energy is emitted, but scattered light obstructs weak incoming uplink signals
Solution Approach 1:
The patent employs pulsed laser transmission instead of continuous wave lasers. The downlink transmitter emits optical energy in periodic pulses with specific timing, creating time windows where transmission occurs and time windows where reception is possible. This periodic action allows the system to alternate between transmitting downlink signals and receiving uplink beacon signals, eliminating scattered light interference from continuous transmission.
Solution Approach 2:
The system uses preliminary synchronization and timing coordination between ground station and satellite. Before actual communication begins, the system establishes precise timing relationships, allowing each side to predict when the other will transmit or receive. This preliminary action enables the satellite to know exactly when to expect uplink beacon signals and when to suppress downlink transmission, preventing interference.
2Power
If high optical power is transmitted on downlink, then sufficient energy reaches ground terminal, but channel separation becomes difficult due to huge power level difference
Solution Approach 1:
By using pulsed transmission with coordinated timing, the system creates distinct time windows for uplink and downlink operations. During uplink reception windows, the downlink transmitter is suppressed or its light is deflected, allowing the highly sensitive uplink receiver to detect weak beacon signals without being overwhelmed by the much stronger downlink signals transmitted during downlink windows.
Solution Approach 2:
The communication channel is segmented into separate time windows for uplink and downlink operations. Instead of attempting to separate channels spatially or spectrally, the patent divides the temporal domain into distinct segments where only one direction transmits at a time, simplifying the channel separation problem.
3Power
If pulsed high-power lasers are used, then minimum optical energy arrives at receiving terminal, but scattered light from outgoing pulses obstructs weak incoming signals
Solution Approach 1:
The system uses pulsed high-power lasers that emit short, intense bursts of optical energy rather than continuous lower power. These pulses are timed so that during the pulse transmission, the receiver is protected or the pulse timing is coordinated with the other terminal's reception windows. Between pulses, there are time windows when the system can receive weak incoming signals without scattered light interference, allowing both high peak energy transmission and sensitive reception.
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 robust communication over long distances with improved signal-to-noise ratio and effective channel separation, ensuring reliable data transmission even at low signal strengths, overcoming the limitations of existing RF technologies.
Implementation Method 1
a pulsed high-power laser source for transmitting a pulsed beacon laser signal into an optical point-to-point uplink channel
Implementation Method 2
Due to the physical effect during opto-electrical power conversion, an increase dP opt in optical power results in an increase of the current dI el at the output of an optical detector
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~6B
AI summary
Bi-directional laser communications system (10) comprising a first transceiver (20) and a second transceiver (30) for establishing two optical channels (A, B) there between. The first transceiver (20) comprises a first transmitter (T1) with a pulsed high-power laser source (22) for transmitting a pulsed beacon laser signal (50) into a first of said optical channels (A). The second transceiver (30) comprises a receiver (R2) with an optical antenna (31) for receiving said pulsed beacon laser signal (50), said second transceiver (30) and/or a receiving optic (31) of said second transceiver (30) being adjustable so that it can be adjusted with respect to said pulsed beacon laser signal (50). The second transceiver (30) further comprises a second transmitter (T2) with a laser (32) for transmitting a high energy laser signal into a second of said optical channels (B), and means (M2) for a separation of said first optical channel (A) and said second optical channel (B). These means (M2) prevent the high energy laser signals from being transmitted into said second optical channel (B) whenever said pulsed beacon laser signal (50) is expected to arrive through said first optical channel (A).