[HN Gopher] Power over fiber
___________________________________________________________________
Power over fiber
Author : rwmj
Score : 326 points
Date : 2024-01-04 10:51 UTC (12 hours ago)
(HTM) web link (chaos.social)
(TXT) w3m dump (chaos.social)
| cwillu wrote:
| From a reply: "wow. I expected expensive (two digits), but
| indeed: these are _very_ expensive (three digits)."
|
| Honestly, seems pretty reasonable for what is likely an
| industrial-grade product. I've paid 80 dollars or so per button
| on a panel with a dozen "simple" push buttons, and there were
| buttons in that same series that went for a few hundred (for
| example https://www.digikey.ca/en/products/detail/schneider-
| electric...).
| genter wrote:
| If you already have the fiber in place, that's dirt cheap
| compared to hiring a sparky to run power for a sensor.
| treesciencebot wrote:
| I don't understand how people find 3V at 180mA usable, isn't
| it like 0.5 watts?
| taneq wrote:
| Watt are you using it for, though?
| ExoticPearTree wrote:
| You can use it for a low voltage relay switch for
| example. Recently got a device that has a small LCD,
| buttons, a small OS and which consumes ~ 20mA at 4V.
|
| Nowadays you can do a lot of things with 3V and 100mA.
| m463 wrote:
| maybe they could power a repeater with it.
|
| (this is a joke btw)
|
| EDIT: wait, what if the repeater was amplifying light going
| the other direction (coming out) or on a different strand?
| aifooh7Keew6xoo wrote:
| then you would have rediscovered the Erbium doped fiber
| amplifier
| lesuorac wrote:
| While light travels pretty far; it doesn't travel
| perfectly inside the fiber. So over time you lose all the
| light.
|
| This can be trivially prevented by have amplifiers
| (analog) along the long cable so that you boost the
| signal's light level. However now we introduce another
| problem where the our nice on-off-on square wave starts
| to look like a gaussian distribution and as it continues
| to degrade it becomes hard to determine a 0 from a 1 (or
| say 00 from 01). So instead of amplifying you have a
| repeater (digital) that re-transmits the original signal
| (assuming it can read it correctly).
|
| Why not just plug the amplifiers and repeaters into the
| grid? They probably do; it's just there isn't a grid
| underwater.
|
| https://www.synopsys.com/photonic-solutions/product-
| applicat...
| londons_explore wrote:
| Thats plenty for a temperature sensor, PIR sensor, humidity
| sensor, door open/close switch, a button, CO2 sensor, etc.
| yetihehe wrote:
| 180mA at 3v is plenty for a lot of pretty beefy
| microcontrollers.
| willis936 wrote:
| It's a perfectly electrically isolated 0.5 W that doesn't
| need a bulky transformer. Let's say you have a sensor +
| tiny computer that you want grounded to a high voltage
| device. You could use this and side step any questions
| about insulation and isolation.
| rkangel wrote:
| That's loads for people who are used to designing
| electronics to run off a coin cell or small Li-On battery.
| My current project avoids peaks of more than 60mA.
| postalrat wrote:
| A capacitor would be useful if you need a spike of higher
| power. If it's the only or you have you will make it work.
| _joel wrote:
| Active power draw (average) of an ESP32-S3 is 78.32 mW. Can
| do quite a lot with that budget.[1]
|
| I'm not sure I'd use this personally, but there could be
| some situation where it's useful I guess.
|
| [1] https://esp32s3.com/
| slau wrote:
| I've designed and installed bespoke industrial cameras
| running on batteries because running any kind of electrical
| cable would require recertification of the entire factory
| floor.
|
| I'm not convinced this fibre wouldn't require
| recertification, but I can guarantee I would've spent the
| time and money to find out if this was an option.
|
| Battery operation and maintenance required SOPs, yearly
| reviews, and a lot of documentation and training.
|
| Quiescent current was in the picoamps, and operation
| spiking in the hundreds of milliamps, which a capacitor or
| two could easily handle.
|
| And if this provides communication as well...
| Aurornis wrote:
| An average AA battery will have 3-4 Watt-hours of capacity.
|
| This 3V at 180mA is 13 Watt-hours in a day.
|
| So think of it like consuming about 4 x AA batteries every
| day, or almost 1500 x AA batteries jn a year.
|
| You can do a lot with that amount of energy. You won't be
| powering a switch or computer, but it's orders of magnitude
| more power than small battery operated devices can use.
| ahmedalsudani wrote:
| A few lemons/potatoes can power an MCU. 0.5 watts is
| luxurious.
|
| https://youtube.com/shorts/qLTEtXY5-BQ
| wkipling wrote:
| At minimum 20pc per order...
| cwillu wrote:
| Digikey stocks them individually:
| https://www.digikey.com/en/products/filter/special-
| purpose-i...
|
| 561.79USD per converter, 540USD if you buy them in packs of
| ten.
| jetrink wrote:
| What separates a $300 button from say a $60 button? Is it like
| an airplane part where has a special rating or is it actually
| that much more reliable?
| cwillu wrote:
| Reliability, ruggedness, flexability, serviceability, lots of
| ilities.
|
| The line of switches I linked lets you snap on independent
| contacts (both normally closed and normally open) that are
| all actuated by the same button, as well as leds in various
| configurations, to a baseplate that fits in a standard hole
| in the panel; the button itself can be swapped out from that
| baseplate for various reasons (recessed, illuminated, a
| rotary switch instead of a button, a giant emergency stop
| button, a 2 or 4-way joystick, etc). Various ratings on the
| whole mess for dust-proof/splash-proof/water-proof/high-
| pressure-wash-proof, which is one of the places where the
| cost starts to go up. Button materials range from relatively
| cheap plastics up to stainless steel, and potentially heavy
| duty enough to survive and continue functioning after blows
| that might shatter a cheaper button.
|
| And you'll be able to order compatible replacement parts 20
| years from now. That's a big part of it too.
| squarefoot wrote:
| > Reliability, ruggedness, flexability, serviceability,
| lots of ilities.
|
| Plus probably some certification+warranty that covers the
| asses of whoever chose that part in case things go bad.
| breischl wrote:
| >you'll be able to order compatible replacement parts 20
| years from now.
|
| Is that because it's an industry standard, or just that the
| manufacturer promises, or something?
|
| Sheer curiosity - I know nothing about this space. :)
| cwillu wrote:
| Promises and history and network effects. Generally you
| more or less buy into a system of instrumentation.
| Obviously you can always run wires from terminal A to B
| across brands, but you can work _much_ more quickly and
| neatly when working with the standard-for-your-shop
| stuff. Your shop will have oodles of terminals and
| buttons and relays in stock, and know exactly where to
| get the oddball stuff, etc. The resellers and supply
| houses all keep inventories. If a part does go end-of-
| life, you'll probably get an email if you've ever
| purchased that part, advising you to make final purchases
| for the long term if needed, etc.
| I_Am_Nous wrote:
| Most of the cool fiber pluggables are a lot more than a couple
| hundred bucks, so when they said expensive I immediately
| thought 4 digits.
| BenoitP wrote:
| > efficiently converts optical power to electrical power
|
| Damn, I thought it was just a copper pair going along the fibers.
| I hope they provide some thick safety glasses with that.
|
| I don't know if it'd come out as laser light, but 600 mW puts it
| into class 4 (eyes are damaged at a few 100m distance):
|
| https://www.lasersafetyfacts.com/resources/FAA---visible-las...
| TheTxT wrote:
| Maybe it can first check if something is on the other end
| before blasting full power
| v7n wrote:
| Something like what? An eye?
| Gare wrote:
| Something that responds to a protocol handshake?
| publicmail wrote:
| I think most high power optics do this already, right?
| onionisafruit wrote:
| So a freemason
| moffkalast wrote:
| _blinks in IEEE_
| mikewarot wrote:
| It does that, if I understand what I read about it a year
| ago.
| NavinF wrote:
| Yeah that's exactly how higher power (compared to 40km SFP
| modules) communication lasers work and why nobody wears laser
| goggles in a data center. Automatically turning the laser off
| when the other side stops responding is ancient tech
| ExoticPearTree wrote:
| You know, in some places there are warning signs that read: Do
| not look into laser with remaining eye
| (https://qph.cf2.quoracdn.net/main-
| qimg-1482f39eeb7fe2a2abc36...).
|
| Anyway, common sense says you don't look with your unprotected
| eye through a fiber endpoint.
| onionisafruit wrote:
| What does that mean? I read it as people who have already
| lost an eye shouldn't risk their only remaining eye, but I
| think I'm missing something.
| ttoinou wrote:
| Yeah it's provocatively funny
| onionisafruit wrote:
| Thanks. I must be awake too early because it didn't occur
| to me the sign is a joke.
| thriftwy wrote:
| The joke being is that's not a joke.
| afandian wrote:
| I think part of the joke is that damage is instantaneous so
| if you're not prepared you can't take evasive action.
| I_Am_Nous wrote:
| On top of this, we can't see 800 nm light. That's well
| into the Infrared band so "invisible lightsaber for your
| eyes" is an exaggeration, but helps visualize what you
| could be dealing with.
| tgsovlerkhgsel wrote:
| It's tongue-in-cheek, implying that many people working
| with the stuff already lost an eye to it.
|
| It's part joke and part telling people "hey, this stuff is
| really dangerous, take it seriously or you'll lose an eye,
| or both". I don't think I've seen a single lab with high-
| powered lasers that didn't have a variant of this sign.
|
| A similar popular sign for chemical labs is "Carol Never
| Wore Her Safety Goggles. Now She Doesn't Need Them",
| depicting a blind woman with sunglasses and a white cane.
| (https://knowyourmeme.com/memes/carols-safety-goggles)
| redog wrote:
| I think that sometimes when humor is added, in this way, it
| is to make you pause first.
|
| At least in my mind when I encounter something oddly
| said/written my mind starts suggesting contexts and I can
| clearly "see" myself going blind by doing me like things.
| marcosdumay wrote:
| It emphasizes that you will only notice there's something
| dangerous around after you are already blind.
|
| It's a very well worded warning, that spread because it's
| effective. The official warning saying that you must take
| precautions even if you don't see anything wrong just
| doesn't work well.
| willis936 wrote:
| What does looking at a laser have to do with being safe from
| a class 4 laser? You could be two rooms over and be blinded
| by it if there are specular surfaces (which there usually
| are).
| jakderrida wrote:
| You probably still shouldn't look into the laser with your
| remaining eye, though.
| xtiansimon wrote:
| "Common sense"?
|
| Never had one of those toys...
|
| https://images.app.goo.gl/nFwVrEe26vkxxJWLA
| xxs wrote:
| You dont have to look at the laser at all, scattered beam can
| be dangerous as well. Note: class 4 lasers have no upper
| bound, they are just hazardous.
| jahnu wrote:
| Have these ever been weaponised?
| cyberax wrote:
| It's against the Geneva Convention to use blinding
| weapons.
| Snow_Falls wrote:
| Has the Geneva convention ever stopped anyone? They can
| only arrest you if you lose the war, and people don't
| tend to plan for that.
| xxs wrote:
| The application would be more civil than war-alike, if it
| existed.
| Snow_Falls wrote:
| That's even harder to prosecute, pretty much no one is
| starting a war over what rulers are doing to their own
| citizens.
| solardev wrote:
| https://en.wikipedia.org/wiki/Dazzler_%28weapon%29?wprov=
| sfl...
|
| They're "intended" to cause only temporary blindness
| cyberax wrote:
| It has. That's why countries don't have real chemical
| weapons anymore. They are easy to make (for an
| industrialized country), but they don't provide any real
| advantage when both sides in a war have access to them.
| They just increase misery for everyone involved.
|
| Blinding laser weapons are in the same category.
| Snow_Falls wrote:
| That's not really the Geneva convention though, chemicals
| weapons are just not effective for any actual warfare
| (aside from committing atrocities).
| robertlagrant wrote:
| Sadly it's not against it to use killing weapons.
| xxs wrote:
| They are called direct energy weapons, more like a sci-
| fi, though.
|
| It'd be a rather short range weapon, that's not easy to
| aim, require a line-of-sight, can't penetrate armor... or
| goggles, or fog/dust.
| adrianN wrote:
| I'm pretty sure high powered lasers penetrate goggles by
| just vaporizing them.
| xxs wrote:
| True but how would you deploy high powered ones and keep
| line of sight?
| paradox460 wrote:
| Use an X-Ray laser, as Larry Niven liked to use as a
| MacGuffin in a few of his stories
| solardev wrote:
| Experimentally, sure:
| https://en.wikipedia.org/wiki/Laser_weapon?wprov=sfla1
|
| Big pewpews require big power and it's not super
| practical yet
| FuriouslyAdrift wrote:
| US Navy has a few deployed and in use
|
| https://en.wikipedia.org/wiki/AN/SEQ-3_Laser_Weapon_Syste
| m
| jnwatson wrote:
| You betcha. I remember in the late 90s an anti sniper
| technology that could detect lenses at long distances and
| fire a laser at them.
|
| The idea was to mess up scope optics, but human heads
| have lenses too. It was not Geneva Conventions friendly.
| andruby wrote:
| I'd love to read more about this. Especially the part
| about the Geneva Convention.
| cromulent wrote:
| I'm guessing it was the Protocol on Blinding Laser
| Weapons.
|
| https://en.m.wikipedia.org/wiki/Protocol_on_Blinding_Lase
| r_W...
| Bluecobra wrote:
| Most fiber/transceivers you commonly find in a datacenter
| won't cause eye damage:
|
| https://www.nanog.org/news-stories/nanog-tv/top-
| talks/tutori...
|
| (slides 79-84)
| mikewarot wrote:
| This is definitely _not_ a most common transceiver, which
| is the point of all the commentary.
|
| I'd refuse to buy this thing unless there was some national
| security reason for doing so, and then there would have to
| be interlocks on the room to de-energize it when anyone
| entered.
| runjake wrote:
| Disclaimer: I recommend you don't look at lasers as a
| standard practice.
|
| For more context, an SFP+ 10G LR 10km module is Class 1
| (completely harmless during normal use).
|
| Same with a 100G LR4 type module.
|
| The ZR type modules that run 100+km are also Class 1.
|
| Pretty much _any_ optical module you plug into a router or
| a switch is Class 1.
|
| Where you should definitely be cautious is:
|
| - Around optical amplifiers, where things can get into
| Class 2 and 3.
|
| - DWDM setups where each module may be a Class 1, but the
| sum of their light adds up into something harmful.
| dpratt wrote:
| "Danger: Not Only Will This Kill You, It Will Hurt The Whole
| Time You're Dying"
| AriedK wrote:
| I find these tremendously helpful https://i.etsystatic.com/13
| 650636/r/il/617182/2062686717/il_... as popularized by AvE
| hotpotamus wrote:
| And if infrared, you won't even see it, and even reflections
| can be damaging to the eyes in theory.
| kiicia wrote:
| green lasers are scaring the heck out of me, each one of them
| is pumped IR laser and each reflection causes green beam and
| IR beam to diverge more and more
| lexicality wrote:
| Looking up the specs, the actual laser is 1.5W, the converted
| output power is 600mW.
|
| The chart you linked suggests that it'll start fires if you
| accidentally break the fibre.
| RCitronsBroker wrote:
| I have several lasers in that category somewhere in the
| depths of the electronics stuff i accumulated from hoarding
| and reselling it for years, including a surplus fiber laser i
| auctioned myself into owning. They can certainly start fires
| under the right conditions, but that requires the fiber end
| to be polished VERY well, otherwise, the beam isn't focused
| enough to deliver the needed energy, bundled up on one spot.
| Still way enough to make you blind before you notice tho,
| nothing to skimp on in any case.
| TheDudeMan wrote:
| Probably the power would stop when the fault is detected.
| avsteele wrote:
| 800 nm (NIR) does present hazards. Most people can't se it
| until the intensity is very high, so you blink reflex doesn't
| protect you.
|
| Having said that, it is probably highly divergent out of the
| fiber (depends on type). There's no risk beyond a few cm. Don't
| stick the fiber it up against your eye though.
|
| To answer someone below its unlikely you could get burned
| except right at the fiber tip. You can stick your hand in a
| 1.5W beam as long as it isn't tightly focused.
| lightedman wrote:
| "it is probably highly divergent out of the fiber"
|
| Those of us in the styropyro discord have found that to
| almost never be the case. WEAR EYE PROTECTION AT ALL TIMES.
| rubidium wrote:
| Agreed. A 40W 1550nm laser I used in grad school would burn
| post it notes readily and slowly burn black painted objects.
| It gave me a little burn once too (Was like touching a hot
| stove). 1.5W focused to 100 um would be a zinger, but at 4 mm
| would be not super dangerous thermally.
|
| The main risk is you couldn't see it so no blink reflex to
| help from even specular reflections.
|
| Regardless, it would be reckless to expose this to people
| without eye protection.
| weberer wrote:
| I think your laser was 40mW. A 40W laser can engrave steel.
| NietzscheanNull wrote:
| Judging by the fact that they mentioned being in grad
| school at the time and that the laser was infrared, I
| imagine engraving steel isn't too far off from what they
| were using it for.
| BenjiWiebe wrote:
| But they mentioned it would slowly burn black painted
| objects.
| xxs wrote:
| Agree on the 3 orders of magnitude difference. 40W
| soldering iron will inflate post-it notes, 40W laser
| steel/stone engraving/cutting area.
| cycomanic wrote:
| Depends highly on wavelength and pulse length. IIRC the
| vast majority of laser engraving lasers are pulsed (the
| cheaper ones are probably qswitched) so 40W actually
| gives you peak powers much higher than 40W.
|
| Igniting something is actually quite different from
| cutting or engraving. Lasers are often so good at cutting
| because they don't deliver enough energy to set things on
| fire, but enough inatantaneous intensity to rip molecules
| apart (have a look at comparisons between femtosecond and
| nanosecond laser cutting for example).
| rubidium wrote:
| Beg your pardon, but I think I would know (PhD in
| experimental AMO physics).
|
| It was one of these:
| https://www.ipgphotonics.com/en/products/lasers/low-
| power-cw...
| galangalalgol wrote:
| Could a fiber break in the wall ignite the sheath? What if
| the Sheath broke as well and it is up against the cardboard
| backing of drywall? Worst case, cellulose insulation?
| cycomanic wrote:
| Cellulose insulation is in fact very flame retardent. But
| to your question yes if the broken fibre was stuck
| against something flammable it could slowly ignite it.
| no_wizard wrote:
| When you say most people, are there in fact people that can
| see this at low intensity?
| NavinF wrote:
| Most (all?) IR lasers leak visible light too. Look into any
| 1310nm SFP module and you'll see red light even though
| 1310nm is well outside the visible range.
|
| And no, this won't burn your eyes out. Despite what the
| clipboard warriors claim, a laser that's designed to couple
| to fiber will not magically focus itself at the exact
| distance where your eyes are located. Instead the beam will
| diverge as if the 1mW laser was a 1mW LED.
| zrail wrote:
| > a copper pair going along the fibers
|
| I learned the other day that this is actually a thing one can
| buy. Direct bury hybrid fiber copper, up to looked like 2 OS2
| strands and 2 12awg copper conductors. It's fantastically
| expensive but might be worth it for certain applications, like
| cameras that are beyond PoE distance limits and also don't have
| power available.
| xoa wrote:
| I wish this was a broadly supported and mass manufactured
| standard and the industry had gone more that way ages ago.
| Optical for data and still have a couple plain strands of
| copper (no need for shielding, twisted pairs etc) for power.
| There isn't any particular reason it should be fantastically
| expensive beyond lack of mass manufacturing and standards. Ah
| well.
| zrail wrote:
| Honestly it probably only helps installation costs, and not
| by much. There are no code issues with running standard
| direct bury copper in the same trench as direct bury fiber,
| nor are there any code issues (iirc, I am not an
| electrician) with running them in the same conduit even.
| Plain direct bury OS2 and 12/2 or 12/3 copper is dirt cheap
| and the fancy cable they use for generators that has 12/3
| plus additional current sense conductors isn't that much
| more expensive.
| Moto7451 wrote:
| With 12AWG, depending on the cable type and rating, you can
| bring 20-30A (90C rated) of power to go with your fiber in
| the same pull. The cable might be expensive but I'm sure the
| use case is great for when you don't want to spend $10,000 on
| bringing a service trunk and meter to where your network
| equipment is being installed.
| dylan604 wrote:
| Sounds perfect for long runs requiring repeaters/boosters
| or whatever kind of inline equipment that could be
| necessary
| wongarsu wrote:
| And power the network gear at the end of the fibre run at
| the same time
| dylan604 wrote:
| Even for remote connections requiring a data line, seems
| like supplying power via solar/battery. Otherwise, you'll
| get some asshat that plugs in their microwave and/or
| kettle and ruins it for everyone else.
| nick222226 wrote:
| Electricians hate this one trick!
| dwater wrote:
| OM4 fiber is rated at 10GB up to 500m or ~1800ft, and the
| amount of current that 12AWG copper could carry at that
| distance with acceptable voltage drop is pretty low, so
| you'd probably still need to be stepping the voltage up and
| down on each end. I looked into this recently daydreaming
| about building a small office in the woods.
| michaelt wrote:
| _> It 's fantastically expensive_
|
| Right now you can buy 50m USB3 cables made of 'Active Optical
| Cable' which is a fiber data link with two copper wires for
| power.
|
| Options start at ~$100 for 50m
| https://www.aliexpress.com/item/1005004105594973.html and
| prices go up to https://www.lindy.co.uk/cables-
| adapters-c1/usb-c449/50m-hybr... - not cheap, but considering
| how few they probably sell and that you're getting a special
| custom type of cable, kinda affordable.
| swores wrote:
| Thanks for sharing.
|
| I can't quite explain it, but... having not known of the
| existence of such cables, and despite the fact that it's
| good I don't have a use for one since they're not exactly
| cheap, there's something about them that makes me want to
| buy one.
|
| I've really no idea why, but I even spent a few minutes
| wondering if there's anything I've never done due to not
| having a cable like that, but didn't think of anything.
|
| (And it's not like I'm a cable collector or enthusiast or
| anything like that, generally!)
| NavinF wrote:
| Move your desktop to the basement and use optical cables
| to connect your monitor and all the peripherals located
| in your room. This is one of the common use cases and it
| was popularized by Linus from LTT. He has optical
| Thunderbolt (PCIe and USB) at his desk and optical
| DisplayPort in several rooms. The latter allows screen
| casting without the usual compression artifacts, input
| lag, and low refresh rate that you get from shoving a
| 32gbps signal down a 1gbps pipe
| swores wrote:
| Thanks! At the moment I'm enjoying my gaming PC adding a
| little bit of warmth in my home office that anyway needs
| heating constantly during the winter anyway... but would
| be tempted to get the PC out of sight in the future.
|
| Any ideas of reputable brands for optical display port
| (and miniDP) cables?
|
| Did a quick search and the first version was PS80 for 10m
| / PS100 for 20m on Amazon from one of those shitty,
| random name Chinese "companies" (in this case called
| "ATZEBE), which wouldn't surprise me if it was actually
| just the cheapest DP cable of the right length they could
| find rather than the real deal. (Not that I'd trust
| buying any cable on Amazon, even one they claim is sold
| directly by a company like Apple, considering Amazon's
| co-mingling system leads to any time they claim "sold by
| x company" has for years actually meant "one or more of
| the stock we have for this item is sold by the company
| that its claiming to be made by, good luck hoping you get
| one of the legit ones".)
|
| And thinking about the two options that user michaelt
| linked in the comment I replied to just above you:
|
| > " _Options start at ~$100 for
| 50mhttps://www.aliexpress.com/item/1005004105594973.html
| and prices go up to [PS450 / $570 USD for 50m at:]
| https://www.lindy.co.uk/cables-
| adapters-c1/usb-c449/50m-hybr..._
|
| To what extent is the expensive one the equivalent of an
| audiophile getting a placebo effect from using overpriced
| audio cables that make no difference in a blind test, vs.
| it being the price needed for a good quality 50m
| optical/hybrid USB cable while the cheap one linked on
| AliExpress might either perform worse, last less long, or
| be an outright scam like those fake USB storage sticks
| that are hacked to tell the OS that they have more
| capacity than they actually do?
| NavinF wrote:
| AFAIK most optical cables are made in the same factory so
| it doesn't matter which one you buy. They also don't need
| controlled impedance like copper cables so it's pretty
| hard for an optical cable to not work
| swores wrote:
| So buying that second option (the Lindy link) is really
| just wasting hundreds of pounds with zero benefit, apart
| from shipping speed, compared to the cheap AliExpress
| option?
| zrail wrote:
| I bought a set of optical HDMI cables for my TV. Not
| because it's a long run, although it is, but because
| they're significantly thinner and I had to get four of them
| through a pretty small conduit. They're pretty nice,
| although I think the cable part is just fiber and each end
| is powered by the device.
| hinkley wrote:
| There was a time they were suggesting structured cabling for
| new buildings, that ran power fiber and coax through the same
| ~1 inch cable. Because you didn't know what you'd want and
| where you'd want it.
| zrail wrote:
| Yep, I remember seeing a variant with 2x Cat5e, 2x coax,
| and fiber. Iirc the argument against them was that they
| were a pain to install in typical residential framed
| construction because the bend radius in reality was like 3
| feet (probably exaggerated, but not by much).
|
| Having now done retrofit Ethernet install in a 75 year old
| house, if I ever build a new house it's going to have low
| voltage conduit from attic or basement to every interior
| wall and one or more big conduits from attic to a single
| home run location, itself with a dedicated 20A circuit.
| hinkley wrote:
| Every time I have to touch wiring I think there's someone
| out there who could get rich figuring out how to make it
| easier to edit the wiring in finished walls.
|
| Though I do know there's a company out there that makes
| manufactured 2x6 stud (tstuds is one name) that's
| basically 2 3x2's with diagonal pins between them.
| Quieter, less thermal transfer, and cheaper to make high
| R outside walls since the cost scales faster with length
| than width. Snaking a new cable through an interior walls
| made of that stuff would just require your typical
| fiberglass pole, with little to no drilling.
| amluto wrote:
| That chart is for _collimated_ lasers. There is nothing
| especially inherently dangerous about laser light, and 1.5W or
| so of light is common (your average household ceiling light is
| in that ballpark). A fiber break is a point source (more
| dangerous especially at very close range) and is a bit focused,
| but it's not going to burn holes in your skin or cornea at any
| appreciable distance. If it's a wavelength that penetrates to
| the retina, then maybe the fact that it's a point source will
| make it more dangerous if it's in focus.
| hinkley wrote:
| This is 35% efficient. 1.5W in and .54W out.
|
| That's not efficient in my book.
| NavinF wrote:
| That's a matter of perspective. Are you comparing to copper
| or to other electrically isolated power transmission tech?
|
| A typical LED is 40% efficient and a typical solar panel is
| ~20% efficient. A typical Qi charger is ~50% efficient. I
| stopped using cables for portable devices a few years ago and
| use magsafe instead which is supposedly has 75% efficiency
| due to perfect alignment of the coils, but that's still
| nowhere close to the ~100% you get from copper cables.
| hinkley wrote:
| I suppose if you're just running one of these, we are
| talking about 8 KWH per year wasted. There are devices in
| my home burning more standby power than that.
|
| If you're running a whole cabinet of these then it's not
| the greatest.
| engineer_22 wrote:
| Approximately 30% power efficiency
| tiku wrote:
| The other 70% can be used to heat your office through the
| fiber?
| masklinn wrote:
| You're not going to heat much with a watt of loss.
| yitchelle wrote:
| For layman, can someone explain how much power are the lights
| emitted? I mean can it be used to burn wood, or the cut through
| sheets of metal.
| Tade0 wrote:
| It's less power than a phone flashlight.
| CoastalCoder wrote:
| But in laser form. Does that change things much?
| zokier wrote:
| Being laser in itself is afaik less of a factor, but being
| IR and a very small spot are more so.
| Sebb767 wrote:
| Now this might be my layman knowledge, but "being a
| laser" seems to imply "a very small spot", no?
| dekhn wrote:
| No, not really. Laser beams have a width and that can be
| adjusted. As it comes out of the fiber, it forms an
| expanding cone which you would then modify with a lens
| (https://content.coherent.com/legacy-
| assets/literature/white_...)
| ben_w wrote:
| Assuming this calculation is correct, from my experience you
| can cut plastic and wood:
| https://chaos.social/@jaseg/111697386931635059
|
| But it won't even _mark_ steel unless you pre-prepare the steel
| with absorbent inks, and definitely won 't cut it.
| dthul wrote:
| I wonder if you could send power at one wavelength, and data at
| another wavelength, over the same fibre.
| CoastalCoder wrote:
| Could they use separate phases of the same frequency, or do
| things like DWDM preclude that?
| zamadatix wrote:
| There's PSK and the likes which mess with phase but I don't
| think that's the same as what you're asking as you would
| typically then use something else to actually get separate
| streams with it. The problem with pure and plain phase
| division multiplexing is how do you separate it back out on
| the other side? You can make up as many pairs of wave values
| to create the resulting wave without doing something else
| beyond plain multiple phases.
|
| Time division multiplexing and frequency or amplitude
| division multiplexing preclude most things because they are
| so cheap and simple these days. Polarity is also another knob
| to mess with when you need to squeeze more.
| raphman wrote:
| Why not both via the same wavelength?
| dthul wrote:
| I was thinking that the "power extraction" might attenuate
| the signal too much, and it would probably lower the power
| output since you need to modulate the light to transmit data,
| instead of having it on full brightness all the time. But
| maybe it would work for certain applications!
| cycomanic wrote:
| Efficiency of laser diodes goes down quite a bit with
| bandwidth. More importantly you typically want the data going
| the other way (from the powered sensor). If you would use the
| same fibre for both directions (might be done for space
| constraints) the issue of using the same wavelength is that
| there are scattering processes (some fundamental to how
| fibres work) in the fibre that will cause some light to be
| back scattered and act like noise essentially. Your sensor
| would transmit with only very little power so the SNR might
| be completely destroyed by the back scatter of the high power
| piwer delivery light. If they are at different wavelengths
| they can be easily separated.
| raphman wrote:
| Oh, you are right - I didn't think about the other
| direction at all. Thanks for the explanation!
| retrac wrote:
| Yes. This is already done. It's how almost all submarine
| communication cables currently work. Most long-distance fibre
| links do not use electronics to regenerate their signals.
|
| They use optical amplifiers, which take light at one wavelength
| and use it to intensify light at another wavelength. They're
| much like lasers (technically I think they count as optically-
| pumped lasers?), and they turn on from a very small input
| signal, effectively reenforcing it.
|
| This can happen across multiple signals, on different
| wavelengths, in parallel. Like a broadband radio amplifier, it
| boosts everything across a large working bandwidth. There are
| even optical compressors (also powered by light), which speed
| up the baud rate of signals. That way a slow electronic system
| can produce the original pulses, and then they can be
| compressed to faster than electronics can work with, and then
| multiplexed with many other signals at different wavelengths,
| and this whole composite thing is sent down the line, amplified
| without decoding along the way, and then finally the whole
| thing is reversed at the other end.
|
| This is the trick behind how fibre links are so fast,
| considering there are no electronics that can handle data
| serially at those speeds.
| pbmonster wrote:
| You're right about submarine fibers, but you seem to suggest
| that the pump light for the laser amplifiers is transmitted
| through the fiber from the cable landing point - like the
| technology discussed in the OP.
|
| That is certainly not the case, the pump light is generated
| from electricity right where the laser amplifier sits in the
| fiber. No real amounts of energy are sent optically down the
| fiber. To power the amplifier, a high voltage DC line is
| designed right into the submarine fiber cable. And those
| things carry a lot of power, a long fiber cable will draw
| tens of kilowatts of DC for all the optical repeaters.
|
| The reason is, of course, that thousands of miles of cable
| has a pretty insane optical attenuation, no matter what you
| do, because optical attenuation rises exponentially with
| length. The electrical resistance of a high voltage DC power
| line only rises linearily, on the other hand.
| petercooper wrote:
| Just to prove I never took physics, where are the photons
| actually going in a long distance undersea cable that makes
| it impossible to just flash a signal across an ocean sized
| length of fiber? (As I had assumed was the case.) Is it
| more a loss of clarity/resolution in terms of wavelength
| rather than the photons going astray?
| drcoopster wrote:
| Think of it as the same as the internal resistance of a
| conductor. Some of the photons are effectively absorbed
| by the fiber and turned into heat.
| petercooper wrote:
| Thanks! I am embarrassingly so much a 'software' kind of
| person that this didn't occur to me, but I get the idea a
| bit better now.
| cycomanic wrote:
| You're right about submarine cables running DC along the
| shielding/armor to power the optical amplifiers. However
| it's worth pointing out that there are so-called "repeater-
| less" systems that do use optical delivery of pump power to
| the amplifiers (typically they combine this with Raman
| amplification). Those systems can deliver high capacity
| communication (not sure where the record stands at but 100s
| of Gb/s to low Tb/s) over >500 km without any electrical
| connection (you still need power at the receiver though).
|
| These are typically used for short submarine connections to
| e.g. connect an island. As it is much cheaper than running
| a full repeatered system.
| etaioinshrdlu wrote:
| How much optical power could be safely carried over such an
| optical fiber in theory? What are the limitations?
| taneq wrote:
| What's your definition of "safely"? :D
| ExoticPearTree wrote:
| not OP, but I put "safe" just a tad below melting point of
| fiber :)
| internetter wrote:
| For glass fiber, that would be 1700C, but you'd need to be
| very worried about any damage if you're anywhere close to
| that
| londons_explore wrote:
| The limitation is the fiber melting. It won't melt along the
| whole length - there will be some bend/crack/dirt which will
| make a hotspot, and that hotspot will then absorb more laser
| light and get hotter, and you'll get a runaway heating. The hot
| bit will then propagate slowly towards the laser source,
| eventually destroying the whole fiber.
|
| High power fiber optic communication systems have protections
| in place to detect this happening and turn off to reduce the
| damage radius.
|
| Learn more: https://www.microcare.com/en-US/Resources/Resource-
| Center/FA...
| zokier wrote:
| Laser cutting machines use optical fibers and can push tens of
| kilowatts if power, although I don't know what sort of fiber
| arrangement they do use. But I think that still indicates that
| you can push a lot of power through fiber.
| bloggie wrote:
| I don't really have numbers for you, but there are currently
| 120 kW+ fiber lasers. A lot of the difficulty is in coupling,
| small defects or misalignment can easily self-destruct.
| (https://www.ipgphotonics.com/en/products/lasers/high-
| power-c...) Commonly used QBH connector
| (https://www.coherent.com/news/blog/qbh-fiber-optic-cables) The
| losses inside the fiber can be small in comparison and less of
| a problem due to manufacturing process control. There are
| efforts to develop hollow-core fibers that may be able to
| couple into free-space with lower loss and risk.
| cycomanic wrote:
| It's worth noting that the word "fibre" should be interpreted
| very loosely when it comes to high power lasers. They are
| often very specialised and in many cases more like "rods"
| i.e. held completely straight as even small bending would
| introduce enough loss to then cause the fibre to melt.
|
| That said you can deliver 100s of W with relatively off the
| shelf fibres.
| vectro22 wrote:
| The target application for this seems to be high voltage
| isolation, and common mode leakage immunity. I could imagine this
| being used to power an active high voltage probe.
| bell-cot wrote:
| THIS.
|
| And in that use case...~1.5W of laser energy would probably be
| way, _way_ down the list of hazards.
| ckocagil wrote:
| It could be used to power a LOT of sensitive test instruments.
| severino wrote:
| Could this idea be used, for example, to power a landline phone
| like it was done with POTS? So no external power was needed for
| the phone and it even worked in the event of a blackout.
| masklinn wrote:
| According to SIN 352[0]
|
| > the average DC current in the loop and voltage across the
| phone will be up to 42 mA at 12.5 V (short line), up to 33.5 mA
| at 10 V, and will be not less than 25 mA at 9 V.
|
| So it's around the same values. However the distances are in a
| different realm entirely: the spec sheet tests over 30m of
| fiber, phone loops range in kilometers.
|
| [0]:
| https://www.openreach.co.uk/cpportal/content/dam/cpportal/pu...
| rwmj wrote:
| Hmm, a class 4 laser going into a consumer landline phone, what
| could possibly go wrong?
| gosub100 wrote:
| it could be done safely with an interlock on the data side.
| if it doesn't get a ping every 1ms it cuts power.
| chx wrote:
| Sure thing. This is 540mW and looking at
| https://electronics.stackexchange.com/a/36495/27147
|
| > headphone jacks typically provide only 10-20 mW of output
| power.
|
| microphones draw even less. A handful of mW is plenty to drive
| even an ARM Cortex M0 not that you need something that complex.
| j4nek wrote:
| I was working i a company (EMC testing) which decided to build
| their own "Power over Fiber" solar cells, also in the 500 or
| 600mW power range. Yes, you can buy such stuff now from boradcom
| but these are simply too expensive.
| j4nek wrote:
| costs were under 10 bucks iirc, same specs.
| csours wrote:
| Ever had one of those retaining clips get weak over time? Yea,
| I'm gonna need some lock out tag out on this cabinet.
| malanj wrote:
| The transmitter module; https://docs.broadcom.com/docs/AFBR-
| POL2120-DS
| Geisterde wrote:
| I am imagining running all the sensors in my data center off
| fiber and not needing a hamster ball of 24v in every cabinet.
| rwmj wrote:
| Getting the server's power consumption down to 500mW would be a
| ... challenge.
| tompccs wrote:
| Must be very niche as lasers operate typically below 10%
| efficiency. And one speck of dust or defect on a component and
| you're setting fire to something.
| Aachen wrote:
| The post says it
|
| > can provide 3v 180mA from 1.5W
|
| 0.18x3=0.54W, so like 1/3 efficient. Maybe that's why it's so
| expensive compared to other modules which can get away with
| lower efficiencies?
| hwillis wrote:
| That's the efficiency of the device, not the laser. This
| device does not include a laser.
|
| That said, I don't know of any diode lasers that are that
| bad. Lasers for this fiber are probably 50%+ efficient and
| even the high frequency laser diodes are still 30%+
| vanderZwan wrote:
| This would still make the whole system a lot less
| inefficient than I expected, tbh.
| auspiv wrote:
| up to 45% efficient at lower power (0.5W in, 0.225W out)
| https://www.farnell.com/datasheets/2785190.pdf
| ajsnigrutin wrote:
| > Maybe that's why it's so expensive compared to other
| modules which can get away with lower efficiencies?
|
| It's expensive, because most people don't need that, because
| they just use a wire to power their device.
|
| This has some very niche uses in high voltage insulation
| (where you need the power on the other side, but really
| really don't want high voltage to travel back down the line
| and destroy your device.
| namibj wrote:
| If you want efficiency you'd use iirc 405nm laser diode plus
| blue LED receiver.
| amelius wrote:
| > 3v 180mA from 1.5W
|
| So only 36% efficient.
| riffic wrote:
| orange site needs a standing rule to avoid linking directly to
| Mastodon instances unless we know they can handle the hug of
| death.
| justaj wrote:
| Have you also recently noticed that Mastodon sites are not
| being archived properly by https://web.archive.org/ ?
|
| It doesn't display any content when viewing the archive. I
| wonder why that is.
| gene-h wrote:
| Powerlight technologies(formerly LaserMotive) has demonstrated
| power over fiber tech that can transmit hundreds of watts[0][1].
| The intended application of this tech was for powering underwater
| remotely operated vehicles(ROV). The same amount of power could
| be transmitted with a thinner fiberoptic cable than a copper
| cable, so it would encumber the ROV less. Although other niche
| applications like powering electronics in regions with EMP or
| near MRI's were suggested. Powerlight's linkedin currently shows
| them powering an inflatable christmas decoration with power over
| fiber.
|
| Some of the people at Powerlight found this tech to be ironic
| because Powerlight was originally founded as a wireless power
| beaming company. However, some of their customers asked if they
| could transmit power via wires, so that's what they did.
|
| [0]https://powerlighttech.com/power-over-fiber/
| [1]https://www.laserfocusworld.com/test-
| measurement/research/ar...
| flakes wrote:
| Thats super cool for the ROV aspect. In university I was part
| of the underwater robotics program, and optimizing the tether
| was a huge aspect. We used a fiberoptic line for communication,
| leaving the rest of the cable mostly dominated by the copper
| conductor for power.
|
| Any weight reduction that can be made for the cable internals
| is actually two fold. The cable needs to remain neutrally
| buoyant as to not pull on the ROV and not restrict the pilot.
| Less internal weight in the cable means less foam/other
| material needs to be added to offset the negative buoyancy.
| anfractuosity wrote:
| Would I be right in thinking a tether would be necessary with
| a ROV for a high bandwidth live video link as ultrasound
| seems only usable up to 100s of kHz.
|
| I guess the only high bandwidth alternative might be lasers?
| gene-h wrote:
| Really bright LEDs can be used for underwater optical
| communication up to 100 m[0]. I'd really like to see
| someone make this tech into an FPV system for RC subs.
|
| [0]https://optics.org/news/11/9/36
| anfractuosity wrote:
| Cool, that's very interesting! I also just found this
| using an array of ultrasound transducers
| https://group.ntt/en/newsrelease/2022/11/01/221101a.html
| for standard definition video.
| ethbr1 wrote:
| It'd be kind of sketchy to have as a single point of
| failure in an underwater ROV that might not be able to
| emergency-surface straight up (e.g. wreck or overhang
| exploration).
|
| There's a ton of gnarly stuff that can happen underwater
| acoustically without obvious warning (salinity,
| temperature, topography, etc etc).
| sandworm101 wrote:
| >>LEDs can be used for underwater optical communication
| up to 100m
|
| Maybe in the clear open sea of the Caribbean. Not all
| water is perfectly clear at any wavelength. I give it
| something more like 100mm through turbid river outflow.
| pi-e-sigma wrote:
| I call bullshit on the claim that you can transfer as much
| energy through optical fiber as through a copper wire of the
| same width. I'm pretty sure they calculate the power
| transmitted taking into account only the 'active' part of the
| fiber, its core which diameter is in micrometers. So it's akin
| to pretending that to transfer electricity you just need copper
| core without the insulators
| beambot wrote:
| I suspect their statement is true if you consider the fully-
| loaded diameter too -- i.e. fiber + cladding can carry more
| power than copper + insulation, especially for small gauges.
|
| Edit: Quick google... This paper [1] shows a 180um fiber +
| cladding carrying 150W over 1km. According to [2], that
| diameter equates to a 33awg wire, which has 678 ohm/km
| resistance and a maximum current of 0.072A. At 1km, the wire
| would be 678ohms. For maximum power transfer, you want the
| load to equal the resistance of the wire. Thus you could
| deliver 0.072A into a 678ohm load - i.e. your maximum power
| would be 3.5 Watts. The fiber is better by 40x.
|
| [1] https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8908
| 271...
|
| [2] https://www.badgerwire.com/tech-info/wire-gauge-table/
| pi-e-sigma wrote:
| Nah, just google 'high power fiber cable', these are used
| to transfer light in laser steel cutters. As these are
| already in practical, industrial use we can assume that
| their spec is in line with what is currently realistically
| achievable for an optical fiber power transmission over a
| distance of a few meters max. For instance a SMA905 Fiber
| Cable can deliver meager 50 Watts and its external diameter
| is 5 millimeters which is laughable low compared to how
| much power you could push through a copper cable with the
| same external diameter, that is including electrical
| insulator.
| beambot wrote:
| I don't think it's a reasonable assumption to look at
| industrial use cases over small distances compared to
| long-distance operations -- the design criteria are
| different.
| pi-e-sigma wrote:
| The design criteria is exactly the same. Have an optical
| medium with as little attenuation as you can. If you
| can't have it in a medium that is only a few meters long
| how could you possibly achieve it in a medium of a few
| kilometers? Apply your logic to copper cables. Can you
| have a copper cable able to deliver power over a long
| distance but unable to deliver the same power over a
| shorter distance?
| quailfarmer wrote:
| The analogy doesn't hold because one of the hardest parts
| of this technology is building a device that can extract
| the optical energy as electrical energy, and dissipate
| whatever heat it generates. The power density of the
| fiber itself is easy by comparison.
| pi-e-sigma wrote:
| The analogy holds perfectly. Remember, we are discussing
| a claim that optical fiber with all required
| cladding/protection can carry as much power as a copper
| wire with all insulation having the same external
| dimension as the fiber cable. It is simply not possible,
| fiber will always have less power carrying capacity and
| your claim that fiber power density is 'easy' has no
| basis in the reality.
| mlyle wrote:
| There's absolutely no reason for the application you
| cited to optimize diameter and isn't approaching physical
| limits.
|
| There's no reason you can't shove many optical fibers
| into that 5mm diameter. People don't, in short distance
| applications, to have simpler systems and connectors.
|
| There's big reasons why we don't use power over fiber
| (the endpoints are very expensive, and the overall system
| efficiencies are low). None of them have to do with the
| highest optical power density you could hit.
| kube-system wrote:
| > The design criteria is exactly the same. Have an
| optical medium with as little attenuation as you can.
|
| If the design criteria for cables was "make a good
| cable", we wouldn't have thousands of different types.
| There are cables which have different mechanical and
| environmental properties, different cost constraints,
| prioritization of different performance characteristics,
| etc.
|
| > Can you have a copper cable able to deliver power over
| a long distance but unable to deliver the same power over
| a shorter distance?
|
| Depending on the particular application, yes. Consider
| some 12/2 solid Romex. It'll handle 10 watts just fine,
| for quite a distance, if you want. Won't work well for a
| 1 meter long phone charging cable, though. Different
| mechanical requirements.
| htgb wrote:
| I know things kind of derailed downthread from here, but
| I just have to add that your claim is either confusing or
| simply untrue. I visited a manufacturer of industrial
| laser welds [1], and they use 16 kWh lasers over
| reasonably small fibers. I don't know the exact
| dimensions, but the overall cable looked like... a
| reasonable cable. Somewhere like 10 to 25 mm perhaps?
|
| [1] https://www.permanova.se/en/our-products/laser-
| source/
| pi-e-sigma wrote:
| The cables look reasonably thin because they are water-
| cooled. That means that the power loss in the cables is
| so great that without active cooling the fiber would just
| melt. Take a look at this page https://www.photontec-
| berlin.com/power_delivery_fiber_cable.... which contains
| actual specs of the cables, for instance
| https://www.photontec-berlin.com/pdf/ld80.pdf or
| https://www.photontec-berlin.com/pdf/ld80-water.pdf
| heisenzombie wrote:
| You're right, though I suspect you could increase that
| "max" current figure quite substantially if we're assuming
| this is an underwater ROV and the wire has water cooling
| for free. You'd need to be pumping a whopping 300A/mm^2
| through that wire to match the 150W fiber, though, so your
| conclusion isn't affected.
|
| Also, your calculation is for equivalent diameters. If mass
| was more important then, well, the fiber is 1/3 the density
| of copper...
| aidenn0 wrote:
| It's been a long time since I did any physics, but explain
| to me why you can't run the 0.072A into e.g. a 10kohm load
| and have 51W of power dissipated in the load? Sure you'd be
| running at several hundred volts, but high voltage is how
| you get more power through less copper.
|
| [edit]
|
| Upon further reflection your claim about maximum power
| transfer being when the load and cable are dissipating the
| same total power doesn't pass the sniff test, because it
| would imply that a load connected by the same 33awg cable,
| but only 1m long could only drive a load of 3.5mW since the
| load would then only be 678 mohm.
| coryrc wrote:
| Your maximum current is too conservative, power
| transmission calculations are conservative enough to run
| wire through fiberglass insulation in a hot attic. Closer
| is "chassis wiring" which rates that wire for 0.47A:
| https://www.powerstream.com/Wire_Size.htm
|
| To deliver 150W with output voltage of 300V (0.5A) would
| require an input voltage of 640V at an efficiency of ~45%.
| Not great. The water could handle a lot higher heat
| distribution but efficiency is already terrible.
|
| > For maximum power transfer
|
| _at a fixed input voltage_.
| onetimeuse92304 wrote:
| Remember, that power is voltage times current. You can
| increase voltage to push as much power as you want through
| any wire. This is the reason why overhead lines use such
| high voltages.
|
| Now, the limitation is the insulation of the wire. The
| insulation will determine how high voltage you can use and
| when you increase voltage, the insulation requirements grow
| very quickly.
|
| The fiberoptic can transfer more power, just not for the
| reason you think it can.
| resters wrote:
| how is this different than the skin effect in wire?
| dragontamer wrote:
| What's the use-case here? That's the biggest optoisolator I've
| ever heard of.
|
| Someone out there wants a lot of power pushed through
| electrically isolated islands. Normally, you'd have power on both
| sides but just send a signal (lower-power light + sensor to
| detect the light). It seems odd to use this technique to transmit
| power (Albeit a small 0.5W worth of power or so, but that's
| enough to run most microcontrollers and even some
| microprocessors).
|
| My guess is some kind of optoisolator situation except you
| weren't allowed to run power on the other side for some strange
| reason. But I'm having difficulty thinking of a practical
| application where these requirements pop up.
| michaelt wrote:
| Products like [1] an oscilloscope probe with +-60,000V
| isolation.
|
| [1]
| https://www.tek.com/en/products/oscilloscopes/oscilloscope-p...
| dragontamer wrote:
| Why would an oscilloscope probe ever draw more than a few mW
| or even microwatts?
|
| I'd expect a normal optoisolator module to work for a probe
| like that. No need for 180mA+ transferred between circuits.
|
| ----------
|
| An oscillator probe is an example where electrical isolation
| + signal (aka: communications) are useful. But under no
| circumstances should 500mW of power be sent through such a
| setup in either direction.
| duskwuff wrote:
| The amplifiers in high-speed active probes can use
| nontrivial amounts of power. I don't have specific numbers
| as the probe/scope interfaces are proprietary, but I
| wouldn't be surprised if some of the wired (non-isolated)
| probes draw multiple watts.
|
| > I'd expect a normal optoisolator module to work for a
| probe like that.
|
| Absolutely not. "Standard" optoisolators tend to be slow
| and have analog characteristics which are unsuitable for an
| oscilloscope.
| quailfarmer wrote:
| Active probes can draw several watts. Probably shouldn't,
| but no one is optimizing them for efficiency
| dragontamer wrote:
| IIRC, leaker and worse-power BJTs handle higher-power and
| have lower noise. (Though Google says JFETs have even
| lower noise).
|
| But the numbers discussed here is a lot more power than I
| was expecting. I'm guessing that at the GHz-range,
| everything uses more power though.
| chemeril wrote:
| I've worked with these exact parts on a few designs for a large
| government institution. Exactly as you suspect: couldn't run
| power/conductive lines to the device on the receiving end for
| physics reasons. But, did work surprisingly well for the
| incredibly impractical use case.
| etskinner wrote:
| Opto-isolators don't transmit power per se. Since they use a
| phototransistor, it's more like they allow power to flow
| through from one pin to another, not provide a voltage across
| the pins.
| Epitom3 wrote:
| The company I work for uses these Cisco Meraki devices in their
| network, some of which support "Power over ethernet".
|
| https://meraki.cisco.com/product/switches/access-switches/ms...
|
| With these devices, you don't need to worry about a separate
| power cable for your network devices.
| TotempaaltJ wrote:
| Fwiw, Power over Ethernet or PoE has been a widely used IEEE
| standard since 2003. This is not specific to Cisco, or Meraki.
| It's common for VoIP phones, cameras, routers, intercoms, etc.
| mcwiggin2 wrote:
| This seems super useful for remote sensors in hostile
| environments.
| cryptonector wrote:
| This could be great for power isolation. Think of a micro-HSM
| application, where you want electrical isolation to protect
| against over/under voltage attacks.
| samstave wrote:
| So... I have a really interesting anecdote on _" Power over
| fiber"_
|
| In ~2004 I was the technology designer for the Lucas Arts
| Presidio Campus - I designed all the physical network, custom
| cable tray in the DC, the DC power infrastructure for the DC and
| did all the layout of the devices collapsing into the DC from
| ILM, Big Rock and other locations.
|
| When we designed the network, it was the largest 10G network in
| the world, all based on FORCE10 equipment, as spec'd by ILM's
| Raleigh Mann (later netword head for Google)...
|
| The original design was for fiber to the desktop, as they wanted
| all desktop machines to become a part of the render farm when not
| being used.
|
| --
|
| We were doing vendor selection from the RFP and holding
| interviews for each vendor to present their response to the RFP
| (The network was ~$50 million (this was 2004, so that was a
| really large number back then)
|
| In the meeting with Cisco, Cisco performed a clown show, but the
| CTO for Lucas seriously (remember, Cisco 6500s was the core king
| at the time)
|
| Lucas CTO: _" Yeah, well we have CAT6 and Fiber to the desktop.
| When can you give me power over fiber so I can just run fiber to
| the desktop"_
|
| Blank stares from everyone.
|
| (He sadly died of heart attack shortly after)
|
| ---
|
| But here we are. We thought a fool, but I guess he was a
| visionary.
| mciancia wrote:
| Crazy that it has been 20 years since 10G was available and
| it's still very uncommon outside of enterprise
| cmpxchg8b wrote:
| I was in LDAC from 2007-2010 and was told that all machines
| could remote boot to join the renderfarm if required, but I
| never actually saw it in action.
|
| Lucasfilm never picked good CTOs. While I was there they picked
| someone from Apple who seemed to be more about marketing than
| anything else..
| samstave wrote:
| It was a money war.... CFO won.
| rini17 wrote:
| Biggest obstacle would probably be the 2/3rds of power which
| ends up as waste heat before it even enters the workstation :)
| jiveturkey wrote:
| > 3v 180mA
|
| i suppose you can't run power and data together, but anyway how
| does this compare to PoE?
| MattIPv4 wrote:
| PoE is around 15w at 48v, PoE+ is 30w, and PoE++ is 60 or 100w
| einpoklum wrote:
| Apparently the price of these things can make a grown man cry.
| orenlindsey wrote:
| Didn't know this was a thing. Pretty cool, but doesn't seem like
| it'd work over long distances.
| NelsonMinar wrote:
| I'm a customer of the very best US ISP (sonic.net) in San
| Francisco. We had a major power outage affecting a quarter of the
| city, including my home. Everything went down. Except my
| sonic.net fiber ISP. I asked the CEO how that worked and he
| responded
|
| > Our network is a "passive optical network" in the outside plant
| - the cabinets on poles just house optical splitters - no
| electronics.
|
| Yes, apparently it's glass all the way from San Francisco to San
| Jose. I'm assuming they aren't using this power over fiber trick
| either but it's neat to think they could, at least for limited
| power needs.
|
| https://twitter.com/dane/status/1190054557667053568
| Animats wrote:
| Years ago, Bell Labs once developed a fiber-optic telephone
| handset that obtained all its power over the fiber from the
| central office. A comment was that the audio wasn't that hard,
| but the bell was really tough.
|
| (It used to be a thing in telephony to be totally independent of
| local power. Landline phones were powered entirely from the
| central office end.)
| wingworks wrote:
| Yep, still a thing here in New Zealand. Though the number of
| people who still have a landline connection at home is dropping
| greatly, and the few that also have a phone which can run off
| the phoneline even fewer. (you need a fairly basic landline
| phone)
|
| Before we got fibre we had our phone just connected to the
| landline and no power, was great, because it always worked,
| power cut, still worked.
| Animats wrote:
| In Switzerland, at least, ISDN phones were powered over the
| phone connection. You could have end to end 64Kb/s
| uncompressed digital voice, the high water mark of telephony
| voice quality.
| Bluebirt wrote:
| Sadly, the bandwidth of the devices is not given anywhere. Would
| be really interesting for certain applications. This is very
| helpful in medic applications like MRI.
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