[HN Gopher] Lasers enable satellite internet backbone, might rem... ___________________________________________________________________ Lasers enable satellite internet backbone, might remove need for deep-sea cables Author : wglb Score : 126 points Date : 2023-06-26 13:57 UTC (9 hours ago) (HTM) web link (techxplore.com) (TXT) w3m dump (techxplore.com) | SiempreViernes wrote: | Great for countries that think they can control space, not so | great for those without ASAT capabilities. | deepspace wrote: | FTA: "However, scaling up is not something Leuthold and his team | will be concerning themselves with". | | As an engineer, the words "devil" and "details" come to mind. | NoMoreNicksLeft wrote: | Why is scaling always necessary? Can't we just do this same | thing, but more of and bigger? I mean, that makes it easy- | peasy. | oneplane wrote: | Because 'more and bigger' can be summed up as 'scaling'... | grimgoldgo wrote: | They transmit in near infrared in an environment that is full of | particles, wouldn't this cause light pollution in a spectrum many | animals would be impacted by? | | Also, doesn't this have the issue that anything passing through | the beam cuts off internet? A bird, a kite, a malicious actor, a | dust storm? | ted_dunning wrote: | There won't be any significant light pollution since the beams | are so narrow. | | The problem of interference from clouds and precipitation is | real, but the problem of physical occlusion probably isn't | because the satellites move pretty fast. That would make it | hard to persistently block the beam unless you have something | as big as a storm cloud. | throwway120385 wrote: | This seems like a reasonable question, on its face. I have NIR | illumination on my surveillance cameras and insects are VERY | interested in it. Every night I get at least one bat hanging | out by my camera. I'm fairly certain it's because the camera | attracts insects. | agnosticmantis wrote: | Aren't lasers extremely susceptible to weather conditions? E.g. | when it's raining/snowing/cloudy, can the base station | communicate with a satellite via laser? | looofooo wrote: | No, it is 1550nm Laser. | adrian_b wrote: | The lasers are used only between the Starlink satellites, not | in the uplinks or downlinks. | | While this experiment has demonstrated that it is possible to | compensate for the turbulence of the air, there is no solution | for the attenuation caused by bad weather. | | It might be possible to use lasers between a base station and | satellites only if the base station is located at high altitude | in a dry place, like those typically chosen for astronomical | observatories, so that the links will be blocked by bad weather | only infrequently. | | So I do not believe that there is even a remote chance of | replacing most undersea cables. | cycomanic wrote: | I like the ETH result and it is an impressive feat (I know some | people involved in that work). That said the article is a lot of | rubbish. First there is the weird focus on lasers, all (relevant) | Optical Communication uses lasers, including fibre comms. Then | they make it sound like this is to replace fibre, again rubbish. | | The amount of data going through fibres is absolutely staggering, | replacing this with intersatellite links is just not going to | happen. First you still need fibre to connect your ground | stations (and you need quite a bit of redundancy due to weather) | and there are still a lot of unsolved problems (tracking and | pointing for example). However there are many interesting | applications of optical satellite links and quite a few players | are investing in it, the big one is actually data connections for | scientific space missions. | Aeroi wrote: | HFT bros jizzing in their pants | cvs268 wrote: | What pants? :-D | ortusdux wrote: | Current fiber optic cables transmit signals at 2/3rds the speed | of light. Modeling has shown that starlink's laser backbone would | allow it to beat deep-sea cables in some situations. This article | estimates a NYSE -> FTSE reduction from 76ms to 43ms. I wouldn't | be surprised to learn that there is a HFT bidding war going on. | | https://archmeregreenarch.org/1456/news/starlink-and-the-ris... | | There is a newer version of fiber optic cable that uses a hollow | core. Testing has shown it transmits signals at nearly the speed | of light. It is very difficult to produce at scale and will | require a generational shift to deploy. | | https://www.nature.com/articles/s41467-020-19910-7 | posnet wrote: | The question isn't whether satellite links can beat deep-sea | cables, it's whether they can beat shortwave. | | https://sniperinmahwah.wordpress.com/2018/05/07/shortwave-tr... | moffkalast wrote: | How can that scale when they need to increase trading volume? | Radio has jack shit in terms of bandwidth. | bhouston wrote: | And HFT setups are also nearly colocated with the exchanges I | understand -- as close as they can get physically, so adding | a hop to space and back may be adding quite a bit of | distance. | heipei wrote: | This would be about reducing latency between these two | exchanges to enable arbitrage opportunities the way I | understood it. | ortusdux wrote: | Exactly. IEX exchange is relatively new, and their big | innovation is that they use long spools of fiberoptic | wire to delay their user's connections, thus creating an | even playing field. | | https://www.sec.gov/files/07feb18_hu_iex_becoming_an_exch | ang... | | _" The reduction in trading costs (spreads) is broadly | consistent with recent theories on how speed advantages | may be used to exploit mechanical arbitrage | opportunities. These theories suggest that market makers | face adverse selection from fast traders even in the | absence of traditional "fundamental" informed trading. | For instance, Budish et al. (2015) defnes "quote sniping" | as the mechanical arbitrage of taking "stale" quotes | before market makers can cancel. In his Comment Letter on | IEX's Exchange Application, Eric Budish argues that IEX's | speed bump may be able to mitigate quote sniping as it | allows IEX's pegged orders to avoid executing against | market orders at stale prices.7 Moreover, cross-sectional | di.erences in spreads in response to IEX's protected | quote are consistent with recent theory suggesting that | exchange speed is a double-edged sword for market makers | (Menkveld and Zoican, 2016). On one hand, faster | exchanges allow market makers to update their quotes | faster, reducing spreads. On the other hand, higher | exchange speed results in a higher probability of quote | sniping. Hence, the results support this more nuanced | view of the net e.ects of speed on trading costs. "_ | willis936 wrote: | "Why is our market crashing" might actually have | something to do with the price of tea in China soon. | tikhonj wrote: | It would be relevant for transmitting information from | different exchanges (NYC = London = Tokyo... etc), not | going from the trading firm's systems to the exchanges. At | a high level, the firms would be making money by helping | markets on different continents synchronize faster. | [deleted] | jdblair wrote: | I think the use case is signalling between exchanges for | millisecond advantages in arbitrage trades, not for trading | on a single exchange. | | See https://spectrum.ieee.org/wall-street-tries-shortwave- | radio-... | ajsnigrutin wrote: | Am I the only one who thinks HFT should be forbidden? Stocks | and investments are a nice thing to have, since you can buy a | share of a company you believe in, they get the money, do | stuff, you get dividends and in the end can sell the stock | after some time too. | | HFT changes these "beliefs in company" to "beliefs that the | stock will go up", and the timeframe of those "beliefs" is | sometimes in milliseconds. This turns classic "investment" into | a computer game with a lot of real money. | criddell wrote: | > you can buy a share of a company you believe in, they get | the money, do stuff | | I think that's only true for IPO shares which often aren't | available to retail investors/gamblers like me. | lend000 wrote: | Where do you think all your liquidity comes from when you | want to buy or sell some instrument? The difference in price | isn't all that substantial if all you do is buy now, sell | when cash is needed in retirement, but if you're that kind of | general index investor, one could argue that your | contribution to markets is actually negative (whereas HFT is | helpful by making prices better and spreads tighter). Buying | SPX makes no differentiation between bad and good companies | in the index and allocates money based on current prices | (which are mainly calculated by HFT's who did the legwork to | get to the current point). | anigbrowl wrote: | No. It's garbage, trading is supposed to serve human needs | and should take place on human timescales. If I had a magic | wand I'd randomly fuzz the timing of trades to remove a lot | of incentives for HFT and some other kinds of automated | trading, which are not much more than banging on a known | deficiency in a slot machine. | | Proponents argue that HFT and other such innovations provide | liquidity to markets; my skeptical take is that this is a | nice technical-sounding term for traders with cash to lowball | falling asset prices. | 542458 wrote: | > since you can buy a share of a company you believe in | | I don't think this is generally true. Stock trading isn't | charity, it's done to make a profit. Almost trading is done | on the basis of second order effects, and has been for as | long as there's been a stock market. Stocks aren't given | value by the company being profitable, they're given value by | what other people are willing to pay for them (okay, yes, | dividends also factor in, but many companies don't pay | dividends and people still assign value to those stocks). | ajsnigrutin wrote: | Well sure it's for profit, but what exactly do we (the | society) get if we allow millisecond investments in our | companies? Compared to classic, long-term investments. | EMM_386 wrote: | The common answer will be "liquidity". | | The honest answer is probably nothing. | patmorgan23 wrote: | Are HFTs taking trades that otherwise wouldn't have | happened? | jfengel wrote: | Is liquidity even a real answer? The HFTs only work | because the market would be made a moment later. A buyer | and a seller already exist. If they didn't, it wouldn't | be high-frequency trading. it would just be "trading". | | As far as I can tell, it neither benefits us, nor costs | us. It siphons off a tiny fraction of money, too small to | notice, but large enough in aggregate. Some parasite gets | to survive, which is annoying if you look directly at it, | but ignorable if you don't. | CameronNemo wrote: | If you have not already looked into it, the Long Term Stock | Exchange (LTSE) is trying to buck this trend and cater to | patient capital. | elif wrote: | HFT isn't even that harmful. What's harmful is brokerages | that hold large portions of financial instruments who take | advantage of customers' live buying and selling with delayed | swaps, intentional front running, etc. This is how the stock | market was bullied before HFT, options markets, trading bots, | etc enabled 'everyone' to do skeezy arbitrage and not just | market makers. | | The only meaningful way to limit the efficacy of these modern | trading styles would be purposeful market friction through | minimum holding times, circuit breakers, etc. You can't just | legislate that people mustnt have low ping.. it's impossible | to enforce. And those market friction mechanisms can create | scary market conditions like backlogs, etc and guess what, | enable market making brokerages to do internal swaps etc. in | spite of the friction and essentially be the only ones able | to bypass restrictions. | bjelkeman-again wrote: | Wouldn't a financial transaction tax be the friction | required? | https://en.wikipedia.org/wiki/Financial_transaction_tax | strictnein wrote: | > HFT isn't even that harmful. What's harmful is brokerages | that hold large portions of financial instruments who take | advantage of customers' live buying and selling with | delayed swaps, intentional front running, etc | | HFT does very similar things, except it's even more opaque | to those not doing it. Large financial firms and exchanges | sell their order data to HFTs. If you're interested in a | deeper dive on what they're doing, a book like Flash Boys | will explain how there's a lot more going on than just a | quicker network connection. | DylanDmitri wrote: | How about forcing public markets to bucket trades within | say 2 second windows, executing best matches at the end of | each period. Low friction and reduces value of millisecond | latency advantages. | phkahler wrote: | >> The only meaningful way to limit the efficacy of these | modern trading styles would be purposeful market friction | through minimum holding times, circuit breakers, etc | | So I occasionally try to think of a reason to have a | guaranteed delay due to signal propagation delay to/from | Mars. Would there be a use for putting an automated | exchange there? Maybe, but then whomever gates the orders | could monitor and predict what will happen 40 minutes out | or whatever. Need TLS from trader to exchange or something. | govg wrote: | You might be interested in IEX [0]. The idea behind that | stock exchange was similar to your thought process - | introduce a guaranteed delay / random offset so that HFTs | can't exploit the markets the way they do others. | | [0] - https://en.wikipedia.org/wiki/IEX | ajmurmann wrote: | Eric Ries with his Long Term Stock Exchange for me really | nailed this issue. HFT is the epitome of all the reasons why | the LTSE is great. | marcell wrote: | What's the actual harm of HFT for the average person? I can | set a $ limit on my orders, so I don't pay more than I want. | Why should I care if some HFT guy scrapes 0.01% value off | each trade? | beirut_bootleg wrote: | It scrapes that % every trade, every millisecond, thousands | of times over. That adds up, and all that money has to come | from somewhere. | lend000 wrote: | That's the price you pay for liquidity, and the | alternative (paying a difference in price far more than | 0.01%) makes everyone worse off except other people | competing in the markets. The money HFT's make comes from | other people trading the zero sum short term trading | game, not you (assuming you are longer term investor or | non-participant in the market), so why should you or | others in your situation get worked up about it? It seems | like either a demonization of that which people do not | understand, a class warfare sort of vibe, or both. | anigbrowl wrote: | * * * | willis936 wrote: | What would that look like? If you rate limit stock exchanges | to something like 1 update per minute then there will likely | be the same amount of networking and computation going on to | speculate on the next update and calculate optimal plays. It | just moves it to behind closed doors where it is harder to | know if shenanigans are going on. | | It would take a heavier hand to push against this problem. | I'm all for it, I'm just not clever enough or knowledgeable | enough to know what would be a good regulation that would fly | in congress. | patmorgan23 wrote: | Small cost per trade (tax/fee) | | Minimum time between buying and selling the same ticker | | Mandatory network 'speed bump' of a few ms between the | exchange and any trading parties | Terr_ wrote: | > What would that look like? | | One attempt is the exchange IEX [0] which introduced a ~350 | microsecond delay to everything simply by running incoming | order data through a ~60km loop of fiber-optic cable. | | Perhaps not the most, er, _featureful_ solution, but it 's | very easy to audit and argue that there are no biases or | backdoors. | | [0] https://en.wikipedia.org/wiki/IEX | vgatherps wrote: | If everybody is exactly 350us slower, then it's still the | same game. | | Iex also offers a variety of (dark) order types that can | pull back without the 350us delay if iex believes the | incoming flow will be toxic | Terr_ wrote: | > If everybody is exactly 350us slower, then it's still | the same game. | | IANATrader, but I don't think that's entirely true. Yes, | it won't stop Carol from getting information from | somewhere and then running in front of Alice to the same | exchange. [0] | | However even fixed-delays [1] can still create | uncertainty about what price your order may actually | execute at when it hits the server, which is something | HFTs rely on more heavily than other traders, since their | strategy depends on high-certainty that they will have a | small positive margin on every trade. | | __ | | [0] I find it geeky-amusing to write (i.e. IEX) or (ex: | IEX) because it feels like the start of a mental tounge- | twister. | | [1] Can't edit my original post anymore, but apparently | there's another 350ms on the outbound path too. | javajosh wrote: | Limit trades to once per hour, then, and require a human to | enter them. | ajsnigrutin wrote: | If you buy a stock, you must keep (hold) it for eg. 30 days | (or 7, or 60, or whatever). | | Compute all you want, whenever you want, but instead of | millisecond timings, optimize stuff for at least some time. | | Maybe even a tax on stock profits, which is really high and | falls after some time of ownership of such stock (we have | this in slovenia, but it's not really high in the first | place, and time brackets go less than 5 years (25%), 5-10 | years (15%), 10-15 years (10%) , 15-20 years (5%), and zero | tax after that. | patmorgan23 wrote: | Even if you said you have to hold it for 3 hours that | would cut against the worst of the HFTs | edgyquant wrote: | There already is a penalty for not holding and a tax on | wash trading (selling and rebuying within 30 days.) | gnopgnip wrote: | Raising the financial transaction tax to 0.1%, 1$ per $1000 | would eliminate the vast majority of unproductive and rent | seeking HFT without negatively effecting liquidity. The US | already has an FTT to fund the SEC, implementation should | be straightforward. Currently the rate is very low, about | 0.002%. Raising the rate would be minimally impactful for | longer term investors and generate on the order of $50b a | year for the government. | | Hong Kong has an FTT of 0.13% currently, it was 0.1% from | 1993-2021 so you can compare HFT impacts on these markets. | Or compare dozens of other countries with similar rates, | Switzerland, Taiwan, France, Italy, Japan. | paulsutter wrote: | do you have a link, love to learn how it worked out in | other places | gnopgnip wrote: | https://www.bnymellon.com/content/dam/bnymellon/documents | /pd... has a good review of several countries laws | robertlagrant wrote: | What's rent-seeking HFT? | lucubratory wrote: | I'm not that person, but presumably it's that someone has | purchased real estate in a geographically relevant | location and constructed property on it/between it and | the exchange which gives them an insurmountable latency | advantage in HFT, and they are characterising the raking | in of cash from that latency advantage as rent seeking. | gnopgnip wrote: | Rent-seeking is an "economic activity to gain wealth | without any reciprocal contribution of productivity". Or | put another way it means societies resources are put | towards wealth transfer instead of productivity/wealth | creation. | karkari wrote: | Is the $50b/year figure estimated after assuming the | 'unproductive and rent seeking' HFT volume is eliminated? | gnopgnip wrote: | Yes, that estimate is with the greatly reduced HFT | volume. And it may not be 100% accurate, HFT and trading | in general could move to another market without these | taxes and/or switch to a type of derivative with a | lower/no tax. Like the UK, for swaps. But these other | markets are smaller and not really a replacement. And | these other markets may pass similar taxes in the future. | Y_Y wrote: | What about a flat "Tobin tax" charged on each transaction | so that it becomes very expensive to do lots of small | trades quickly and encourages doing bigger trades at lower | frequency? | | https://en.m.wikipedia.org/wiki/Tobin_tax | ortusdux wrote: | A few congress people put forth a bill that would add a | 0.1% tax on trades. This would be a rounding error for most | traders, but a significant value for HFT. | | https://www.brookings.edu/opinions/congress-wants-to-tax- | sto... | | I wonder what happened to it. | [deleted] | Loughla wrote: | Honestly, I don't understand how they're legal, either. HFT | just seems like the most naked of naked cash grabs in | finance. | tails4e wrote: | I agree. HFT goes against the original ethos of a market open | to all. Instead of trading on the merit of a given company, | it simply reinforces the market is increasingly gamified and | unfair. It's like futures, no ones cares about the commodity | being traded, or that doing so can really hurt people and | business that rely on that item, it's just another item to be | gambled. | pravus wrote: | > HFT changes these "beliefs in company" to "beliefs that the | stock will go up" | | No, this is the part most everyone gets wrong about HFT. | These systems make money off of volume, not price. They don't | care if the price is going up or down. All they care about is | that they can capture a small price delta by facilitating a | trade faster than someone else and they are willing to do so | for smaller fractions of a cent which makes them more | attractive to all market participants, including you and your | retirement funds. Their concerns are orthogonal to investors | and they compete with other HFT firms and market makers. | Xcelerate wrote: | I have a suspicion that at some point, an HFT group will | obtain a brief but substantial lead in machine learning (a la | RenTech, but on a shorter timeframe) that allows them to suck | a decent amount of money out of the stock market before | anyone else can respond or close the gap. We probably won't | get any sort of regulation until after that happens. | vgatherps wrote: | Hft groups are about 15-20 years ahead of you on that | cortesoft wrote: | In a healthy market, HFTs serve as market makers, and allow | normal traders to have faith that prices will be consistent | at all exchanges. If there is enough competition, an HFT will | have very low profit. | [deleted] | gorkish wrote: | > require a generational shift to deploy. | | Photonic bandgap / Bragg fiber is being produced in quantity, | and some subsea cables are using it. | | I'm pretty sure it's the satellite lasers that require the | generational shift. One subsea cable has no bearing on any | other; once the first is installed, you're up and running. not | so with laser-connected swarms. | ortusdux wrote: | Starlink's laser connections have been active for a year now. | cma wrote: | What's the latency NY to Australia all over Starlink with | laser interconnect now? | modeless wrote: | I don't know if Starlink is routing packets that way. I | think it's more likely that they route packets to a | ground station as soon as possible to save laser link | capacity for customers that actually need it, like ones | in the middle of the ocean. If you want your packets | routed all the way around the Earth through space then | you'd probably need a special contract with SpaceX. | thesz wrote: | [1] https://wccftech.com/starlink-turns-on-laser- | satellites-for-... | | Judging from [1], lasers are used not for inter-satellite | links, but for downstream or upstream links - from | satellites to the ground. | | Intersatellite links require precise machinery, such as | picometer-precise positioning systems [2]. | | [2] https://www.pi- | usa.us/fileadmin/user_upload/pi_us/files/prod... | | Also, there should be compensation for satellite rotation, | initial targeting and tracking. At ~12km between satellites | (~4000 on 550 km orbit), the (possible) target of laser | signal receiver which, say, is one meter in diameter will | be one third of an angular minute. It is not impossible to | target that initially, but keep in mind that laser beam is | very focused and its power drops significantly with the | angular distance. | | I really do not know how to even target satellites' | receivers initially, let alone compensate for rotation and | track these targets afterwards. | ortusdux wrote: | From [1]: | | _" Space lasers allow Starlink satellites to connect | directly to one another, eliminating the need for a local | ground station and enabling Starlink. to deliver service | to some of the most remote locations in the world - like | Antarctica."_ | wmf wrote: | Don't read WCCFTech; they don't know what they're talking | about. | | AFAIK the satellites within an orbital plane are | stationary relative to each other, so once the laser is | aimed it should stay connected. | cycomanic wrote: | Photonic bandgap fibres are not used in submarine cables | their loses are too high. There are recent antiresonant | fibres (NANF) which can achieve lower losses than even SMF. | However production capabilities are not ready yet to make the | amount of fibre necessary for submarine. The startup (out of | Southampton) that pioneered these was recently acquired by | Microsoft. | | We probably see these fibres for links between the exchange | and data centres first (although there it is difficult to | beat RF links, as they are direct line of sight) | [deleted] | [deleted] | HWR_14 wrote: | Wouldn't they have to relay between many satellites due to line | of sight? And wouldn't that eat up any decrease in time of | flight for the signal itself? | nine_k wrote: | I suspect that retransmission with amplification only, | without much processing, can be really fast. Modern | electronics can routinely do sub-nanosecond latency. | londons_explore wrote: | Indeed. If the system is designed with latency in mind, | then the receive to send latency can be as low as a few | feet of distance equivalent. | activiation wrote: | HFTs are in the nanoseconds range, not milliseconds... They | rent space AT the exchanges... They remove firewalls and such | to shave even more time | client4 wrote: | Only within the DC, not between exchanges. | [deleted] | sleepybrett wrote: | Used to work, in the early naughts, for a company that had a | laser uplink in seattle from their office building to the westin. | I sat in the office with the uplink for awhile, pointed out the | window with a big gimble, you could watch it adjust for building | sway. | | Uplink went to shit in heavy fog though... | samtho wrote: | This tech is really cool, but as they mentioned, they have not | tested this with a moving satellite. Because any antenna would | need to be localized on a satellite for transmission, you're | going to be stuck with having to maintain (likely) expensive and | precise motors who's job it will be to run in perpetuity. | However, I would be confident that stepper motors of this grade | will come down in price or will become more available. | | My primary concern comes down to reliably. Your ground station | must now accurately target moving satellites, negotiate handoffs, | and reroute when necessary. Architecturally, you will need to | develop the ground station with at least three transponders: an A | link, B link, and a redundant Z link. The A and B take turns | localizing to their satellite where one is only allowed to move | positions if the other is currently active. The backup Z link is | on standby in case of failure or maintenance. The three would | likely rotate roles periodically to keep time on each of the | motors more evenly distributed amongst them. This system must | work in harmony with all the satellites in its network. The | satellite system has its own maintenance burden too, including | orbital decay requiring you to periodically adjust its position | until it runs out of propellant, and send more up when it's | reached the end of its useful life. To me, this is a ton of | moving parts. | | An undersea cable by contrast, will pretty much be maintenance | free once laid only requiring infrequent repairs in the event of | a wayward ship anchor. Yes, the data center components will need | to upgraded periodically but you don't need to replace the | transmission mode. There are no moving parts, no need To track | objects hundreds of miles away, just sending light down a tube. | | Is this tech cool? Absolutely. Will it replace undersea cables? | Probably not soon, but I can see this as a great solution to link | remote islands where it does not make strategic sense to run a | cable, or where it is difficult or uneconomical to run a | terrestrial connection. | colinsane wrote: | > Because any antenna would need to be localized on a satellite | for transmission, you're going to be stuck with having to | maintain (likely) expensive and precise motors who's job it | will be to run in perpetuity. However, I would be confident | that stepper motors of this grade will come down in price or | will become more available. | | the article says they direct the laser using a MEMS device. not | dissimilar to the micromirror arrays used in DLPs for decades, | i would assume. you've definitely got options that don't | require stepper motors or any macroscopic moving parts here. | hbogert wrote: | are they trying to the feed the flat earthers? | 1970-01-01 wrote: | Last I checked, there is a 1% chance of a Carrington Event within | the next decade. Leaving cables behind and trusting new wireless | links before we have a "full DR" situation would be stupid. | okasaki wrote: | Neat, but won't it be slower? | CorrectHorseBat wrote: | It should be faster, the speed of light in optical fiber is | only 2/3 of that in vacuum (and air). I'm more concerned about | clouds and storms. | Havoc wrote: | I could see both being in use, but replacement seems unlikely to | me. | | If nothing else I could see governments insisting on both just | for strategic reasons. Both techs are vulnerable to being fk'd | with so doubling up makes sense | aj7 wrote: | I suspect the tracking and switching infrastructure, the | sophistication of free space lasers with their adaptive optics, | and the inclusion of satellite receiver-transmitters with their | own adaptive optics will not be competitive with laying a passive | undersea cable for at least a decade. | supriyo-biswas wrote: | Does it bring any latency improvements for users? | _R_ wrote: | Hope to see it deployed in GEO, as this would significantly | increase bandwidth and reduce costs in remote areas. | huijzer wrote: | Eliminate deep sea cables? How are they going to send the lasers | in a curve from one base station to the next? | | Starlink is already working on a backhaul from satellite to | satellite. Interestingly, they claim that they can speed up data | transfers by 50% over long distances. Musk said that in a Tweet | which I cannot find now. I looked a bit into it and the reason | seems to be that light trough a cable can only reach 70% of the | speed of light while lasers through the vacuum of space can reach | the speed of light. | toast0 wrote: | Sending lasers in a curve should be easy if you use circular | polarization. /s | | You would send to a satellite in view; my orbital dynamics are | poor, but I think with the LEO orbits, you may need to relay in | space for a cross ocean link, as it seems unlikely one satelite | would have a view of both sides. But Telstar 1 and 2 were used | for cross-Atlantic microwave relay with a single satellite in | view at a time. Future Telstars were geostationary, because | satellite tracking was a lot of work (and with only two | satellites, service was intermittent as they were only in view | for a portion of their orbits). I imagine satellite tracking | for lasers is going to be very difficult as well. | ackbar03 wrote: | How hard can it be | Tuna-Fish wrote: | To be clear, Starlink is already doing this. Their | satellites have laser links that connect them to each | other. | ceejayoz wrote: | They've launched satellites with laser links, but I don't | think they've got the satellite-to-satellite links active | yet. https://www.starlink.com/technology says "testing" | for that feature. | Tuna-Fish wrote: | The website is out of date. | | They are already providing service over open ocean out of | reach of one hop to base station. | dlisboa wrote: | > How are they going to send the lasers in a curve from one | base station to the next? | | All you need is a well-placed black hole in Earth's atmosphere. | ceejayoz wrote: | > Eliminate deep sea cables? How are they going to send the | lasers in a curve from one base station to the next? | | Multiple satellites. The ISS can see about a thousand miles in | each direction to the horizon, so you'd only need to bounce | across a couple to cross the Atlantic. | [deleted] | Aaargh20318 wrote: | > Eliminate deep sea cables? How are they going to send the | lasers in a curve from one base station to the next? | | They use a special laser that gives the photons a bit of | topspin. | ryanwaggoner wrote: | Sure, because we only need the internet on sunny days. | teeray wrote: | I genuinely hope one of these systems gets called "Tightbeam" | CAP_NET_ADMIN wrote: | > Although the laser system was not directly tested with an | orbiting satellite, they accomplished high-data transmission over | a free-space distance of 53km (33 miles). | | This is peanuts compared to under sea cables and issues you will | find penetrating atmosphere and increasingly, space. | | We should keep under sea cables and work on additional | connections to make our networks more resilient, both to natural | phenomena, equipment failures and sabotage. | pushfoo wrote: | > more resilient, both to natural phenomena, equipment failures | and sabotage. | | I think you're understating the risks from geomagnetic storms. | In comparison to satellites, fiber optic cables seem like | they'd be relatively unaffected even if the equipment attached | to them needs replacement. | zamfi wrote: | Perhaps the ocean is protective to some degree, but beyond | very short lengths undersea cables have powered repeaters | that draw considerable current, and which would plausibly be | destroyed if the base stations are too. | adrian_b wrote: | I would not say "very short lengths", because undersea | cables without powered repeaters (only with optical | amplifiers) are possible until a few hundred kilometer. | | But you are right that transoceanic cables need powered | repeaters. | CAP_NET_ADMIN wrote: | Currently, you can cut internet connections to most countries | with a small deep water sub. China, for example, was busy | building one that can be used at 10k+ depth and has arms. | giobox wrote: | Its widely assumed China, Russia and the US have "kinetic | kill" abilities on satellites in space too, its just | capabilities are not as widely known. Projects Like the | US/Boeing X-37 space drone etc, whose purposes still | haven't really been revealed: | | > https://en.wikipedia.org/wiki/Boeing_X-37 | | Russia has already demonstrated its satellite destroying | tech: | | > https://www.cnbc.com/video/2021/11/16/russia-blows-up- | satell... | wcoenen wrote: | Also, India. List of anti-satellite tests: https://www.re | searchgate.net/publication/368223169/figure/tb... | CAP_NET_ADMIN wrote: | "Kinetic kill" is arguably easier to detect and harder to | deny. | | I haven't said that we should only focus on sea cables, I | said that we should do both so that the overall | reliability and resiliency increases. | kelnos wrote: | Can those be deployed "anonymously" though? Publicly | destroying another nation's satellite would be an act of | war. Quietly and secretly cutting an undersea cable, | while being able to plausibly deflect blame, is a bit | safer. | elzbardico wrote: | The problem is that it is fairly difficult to do it | cleanly without risking precipitating Kessler syndrome. | https://en.wikipedia.org/wiki/Kessler_syndrome | | It is basically automatic MAD (Mutually Assured | Destruction) out there in space. | piyh wrote: | Are solar storms an issue for LEO sats? | irq-1 wrote: | off topic: NASA is working on lasers in space. | | > The Deep Space Optical Communications (DSOC) package aboard | NASA's Psyche mission utilizes photons -- the fundamental | particle of visible light -- to transmit more data in a given | amount of time. The DSOC goal is to increase spacecraft | communications performance and efficiency by 10 to 100 times over | conventional means, all without increasing the mission burden in | mass, volume, power and/or spectrum. | | https://www.nasa.gov/directorates/spacetech/tdm/feature/Deep... | JoshTko wrote: | We should keep both, Solar flares, space junk, etc. can knock out | satellites | NelsonMinar wrote: | The key thing here is it allows for very high bandwidth to go | almost anywhere on earth, not just spots where it's easy to land | a cable. Starlink's already demonstrated how great that is for | consumer bandwidth (50Mbps); a multi-gigabit link terminated at a | satellite is fantastic. | | The part that impresses me most is they're talking about LEO | satellites. Those move fast! Starlink does this with a very | impressive phased array antenna design. Conceptually tracking a | moving satellite with a laser is as easy as rotating a mirror, | not sure how hard it is in practice. | nottorp wrote: | > how great that is for consumer bandwidth (50Mbps) | | 50 Mbps is great consumer bandwidth where? | littlecranky67 wrote: | Almost everywhere in Germany. | NelsonMinar wrote: | Sadly, in most of the rural US. My other options are 12Mbps | fixed wireless, 1-100Mbps cellular, or 3Mbps DSL which AT&T | stopped selling in violation of various government contracts. | | Starlink in practice is 10-200Mbps. Here's their | specifications: | https://www.starlink.com/legal/documents/DOC-1138-34130-60 | UI_at_80x24 wrote: | Rural Canada. On a lake shore. 30km from one of Canada's "Top | 50" cities. | | Where I used to live, I had 2 options for internet access. A | Wireless ISP that uses a parabolic antenna pointed at a | water-tower about ~20km from my home; or a cell-phone based | internet connection. | | The WISP allowed me on average 300kb/s transmissions. The | Cell-Phone allowed me between 1.5Mb/s and 7Mb/s (to a max use | of 5GB/month). | | So 50Mb/s is an incredible upgrade. | bcrl wrote: | Sounds like your WISP isn't investing in the new generation | of massive MIMO radios made by companies like Cambium. | NohatCoder wrote: | An actual 50 Mbps link is perfectly good for most use cases, | you can stream anything and it is not really a bottleneck in | determining how quickly pages load. Large file transfers may | still take appreciable time, but it is rarely a big issue. | | An advertised "50 Mbps" mobile connection is dog food if you | are used to 50 Mbps fiber. You are lucky if you get 20 Mbps | through, though it can be much less. Worst part is all the | packet loss that cause inconsistent latency and speed. | nine_k wrote: | In most places where you can't economically get a fiber. That | is, in most places outside dense urban cores. They are petty | numerous in the US. | lm28469 wrote: | I'm on 50mbps and 99% of the time it's too fast for my needs. | I've lived on 10mbps capped 4g for a month and I didn't | notice any problems either | | Anything that allows video communication/streaming is "great" | imho, it certainly is more than enough for most people. | oceanplexian wrote: | It also circumvents the biggest problem with fiber, politics. | Starlink doesn't need permission to run a backbone across (or | rather over) a country. This will be revolutionary for people | in Africa, South America, and huge swaths of Asia/Australia | where a few telecom monopolies have artificially jacked the | price of transit. | falcolas wrote: | IIUC, it only circumvents politics due to existing treaties. | Those old treaties are likely ripe for revision with the | extensive commercialization and the increasing number of | countries capable of launching payloads into space. | | https://en.wikipedia.org/wiki/Politics_of_outer_space | thecosas wrote: | It definitely helps mitigate the infrastructure buildout | hurdles (which are not small), but they would still need to | jump through any "I need to do business in this country" | regulations, etc. | looofooo wrote: | https://en.m.wikipedia.org/wiki/Chappe_telegraph | | Might be cheaper to build an Tower with PV and battery every 30km | than running lines. | | Cell-Tower in remote Locations etc. | nine_k wrote: | Congrats, you've reinvented microwave lines, widely deployed in | exactly this manner. | Tuna-Fish wrote: | The big difference between open air laser and microwave links | is that one of them doesn't require licensed spectrum. The | costs of doing it will be much lower. | nine_k wrote: | Fair! And the existing MW re-translator towers can be | upgraded / reused this way. | | Lasers have a downside though: optical and near IR light is | much more readily absorbed by water vapor than microwaves. | I wonder if a maser would be an acceptable solution, if | cheaper versions of it existed. | looofooo wrote: | 1550nm water is super transparent. | adrian_b wrote: | Not at all. | | While 1550 nm falls between two absorption maxima of | water, so it is not the worst choice, the absorption in | water is still more than one hundred times higher than at | e.g. 905 nm. | | Because of this, 1550 nm is absorbed through fog or | clouds at least 3 to 5 times more than shorter | wavelengths like 905 nm. Even the latter is absorbed a | lot by water, while being much more dangerous for eyes | than 1550 nm. | | There is no near infrared wavelength where the water | absorption is negligible. | | See the graphs at: | | https://en.wikipedia.org/wiki/Electromagnetic_absorption_ | by_... | looofooo wrote: | Microwave is also slow compared to this. | bcrl wrote: | I'm sure regulators will start regulating the 1550nm | spectrum once they realize they can start making money off | free space optics. | eqvinox wrote: | This sure sounds useful, but "might remove need for deep-sea | cables" is quite silly. | | Anything they do to cram bandwidth into their laser link can | reasonably also be applied to fiber optical cables. Except the | fiber optical cables come in bundles of 12 to 144 with absolutely | no separation issues. Replicating that over open space (air or | vacuum), if reasonably possible at all, will chug significant | amounts of power in signal processing at the receive end. | | There are major benefits to free-space optics - | | - quicker to build | | - lower latency | | - in some cases, large coverage | | But deep-sea cables compete on bandwidth, and that's not | something free-space optics can beat them on. Why diminish this | research achievement by conflating it with that? :( | NohatCoder wrote: | On top of this I really doubt the claim about working in bad | weather. Some weather will work, sure, maybe at reduced speeds. | But if there is a proper cloud in the way, the near-visible | 1550 nm light will be scattered completely. | giantrobot wrote: | I believe the idea is that the ground link is still radio but | the interconnect between the satellites is a laser. While | radio can be affected by weather, the "works in bad weather" | is a long solved issue. | dylan604 wrote: | what is a proper cloud? it does not seem to be a term | frequently used when discussing clouds: | https://en.wikipedia.org/wiki/Cloud | IshKebab wrote: | Is this parody? | dylan604 wrote: | Not any more than saying a "proper cloud" will disrupt | satellite transmissions is meant to be serious. Is it a | cirrus cloud? Is it a cumulus? A cumulonimbus? Which | cloud is going to do this blocking? | staunton wrote: | This really isn't that complicated. You can't do a link | through pretty much any cloud where you would say "it's | cloudy". If you're not sure, the link still works but a | lot worse... | nvahalik wrote: | Not to mention stuff like Solar flares. ___________________________________________________________________ (page generated 2023-06-26 23:00 UTC)