3 ms·

Powerlight technologies(formerly LaserMotive) has demonstrated power over fiber tech that can transmit hundreds of watts[0][1]. The intended application of this

by gene-h 3y ago

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/ https://powerlighttech.com/power-over-fiber/ [1]https://www.laserfocusworld.com/test-measurement/research/article/16561660/lasermotive-announces-laser-power-over-fiber-technology https://www.laserfocusworld.com/test-measurement/research/ar...

flakes 3y ago
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 3y ago
  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 3y ago
    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 https://optics.org/news/11/9/36
    - anfractuosity 3y ago
      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 https://group.ntt/en/newsrelease/2022/11/01/221101a.html for standard definition video.
      - ethbr1 3y ago
        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 3y ago
      >>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.
  - flakes 3y ago
    Wireless signals can drop off very quickly even in clear water. Add dirt, algae, turbulence, etc to that and it quickly drops off in about a meter for reasonable devices. For our bot we had about 3 1080p video streams being sent back over the wire, which requires a decent amount of bandwidth (we used a small fiberoptic ethernet switch on the surface and inside the enclosure). Apart from that, if your ROV is light, and the cable is durable enough, the cable can make for a good retrieval method when you brown out the bot haha.
pi-e-sigma 3y ago
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 3y ago
  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=8908271&casa_token=W_8YBHm8hssAAAAA:86Dy1EppIMO4Inbg7u6ZAEciApnsS5-DbJ0wAWPSiOQdHDhbksO7BE-8j8BWQHCr5CXjW1CyODh5yJQ&tag=1 https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8908271... [2] https://www.badgerwire.com/tech-info/wire-gauge-table/ https://www.badgerwire.com/tech-info/wire-gauge-table/
  - pi-e-sigma 3y ago
    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 3y ago
      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.

by gene-h 3y ago

flakes 3y ago

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 3y ago
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 3y ago
  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 https://optics.org/news/11/9/36
  - anfractuosity 3y ago
    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 https://group.ntt/en/newsrelease/2022/11/01/221101a.html for standard definition video.
    - ethbr1 3y ago
      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 3y ago
    >>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.
- flakes 3y ago
  Wireless signals can drop off very quickly even in clear water. Add dirt, algae, turbulence, etc to that and it quickly drops off in about a meter for reasonable devices. For our bot we had about 3 1080p video streams being sent back over the wire, which requires a decent amount of bandwidth (we used a small fiberoptic ethernet switch on the surface and inside the enclosure). Apart from that, if your ROV is light, and the cable is durable enough, the cable can make for a good retrieval method when you brown out the bot haha.

pi-e-sigma 3y ago

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 3y ago
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=8908271&casa_token=W_8YBHm8hssAAAAA:86Dy1EppIMO4Inbg7u6ZAEciApnsS5-DbJ0wAWPSiOQdHDhbksO7BE-8j8BWQHCr5CXjW1CyODh5yJQ&tag=1 https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8908271... [2] https://www.badgerwire.com/tech-info/wire-gauge-table/ https://www.badgerwire.com/tech-info/wire-gauge-table/
- pi-e-sigma 3y ago
  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 3y ago
    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.