Bi-Directional Optical Link with Pulsed Beacon Channel Separation
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Solution Overview
Problem
Current communication systems between ground stations and deep-space satellites face challenges in maintaining robust communication over long distances, particularly in separating optical uplink and downlink channels due to significant power level differences, which complicates channel separation and increases noise interference.
Innovation Solution
A bi-directional laser communication system employing pulsed high-power lasers for beacon signals and active channel separation, where the downlink transmitter is inhibited or deflected during beacon pulse arrival to prevent scattered light interference, allowing independent optimization of link budgets and using modulation schemes like PPM to enhance signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high optical power is transmitted on the downlink to ensure detectable signal at ground terminal, then signal energy at receiver is improved, but channel separation becomes difficult due to huge power level differences between uplink and downlink
Solution Approach 1:
The patent applies periodic action by using pulsed laser transmission instead of continuous wave transmission. The downlink transmits optical signals in periodic pulses, and the uplink beacon transmission is synchronized to occur during the intervals between downlink pulses. This temporal separation allows the ground terminal to receive uplink beacons without interference from downlink transmissions, and allows the space terminal to transmit uplink beacons without being overwhelmed by scattered downlink light, thereby solving the channel separation problem while maintaining reliable communication
2Power
If narrow pulse duration is used to increase bandwidth, then electrical signal power increases by square law, but electrical noise power increases linearly with bandwidth
Solution Approach 1:
The patent applies parameter changes by optimizing the pulse duration and repetition rate of the laser transmission. By using very narrow pulse durations (on the order of nanoseconds or picoseconds) at high repetition rates, the system exploits the square-law relationship where electrical signal power is proportional to the square of the optical power, while the noise power only increases linearly with bandwidth. This parameter optimization allows the signal-to-noise ratio to improve significantly, enabling reliable detection of extremely weak optical signals from deep space
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 reliable and robust communication over long distances by ensuring clear channel separation and increasing the signal-to-noise ratio, effectively addressing the limitations of existing RF technologies in deep-space communication.
Implementation Method 1
Due to the physical effect during opto-electrical power conversion, an increase dPopt in optical power results in an increase of the current dIel at the output of an optical detector
Implementation Method 2
The first transceiver comprises a first transmitter with a pulsed high-power laser source for transmitting optical beacon pulses
Implementation Method 3
prevent with a certain degree of certainty said high energy laser signals from being transmitted into said second optical channel whenever said optical beacon pulses are expected to arrive
Data Source
AI summary
Bi-directional laser communications system comprising a first transceiver and a second transceiver for establishing two optical channels there between. The first transceiver comprises a first transmitter with a pulsed high-power laser source for transmitting a pulsed beacon laser signal into a first of said optical channels. The second transceiver comprises a receiver with an optical antenna for receiving said pulsed beacon laser signal, said second transceiver and/or a receiving optic of said second transceiver being adjustable so that it can be adjusted with respect to said pulsed beacon laser signal. The second transceiver further comprises a second transmitter with a laser for transmitting a high energy laser signal into a second of said optical channels, and means for a separation of said first optical channel and said second optical channel. These means prevent the high energy laser signals from being transmitted into said second optical channel whenever said pulsed beacon laser signal is expected to arrive through said first optical channel.